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Lake Shore Model 625 Superconducting Magnet Power Supply

1. OUTPUT WARNING 625_Rear bmp Figure 3 1 Model 625 Rear Panel 3 2 Installation Lake Shore Model 625 Superconducting MPS User s Manual 3 3 LINE INPUT ASSEMBLY This section describes how to properly connect the Model 625 to line power Please follow these instructions carefully to ensure proper operation of the instrument and the safety of operators 100 120 V 10 0 AT 250 V 0 25X1 25 100 120 220 240 V 10 6 Voltage 50 60 Hz 850 VA MAX Line Input bmp Figure 3 2 Line Input Assembly 3 3 1 Line Voltage The Model 625 has four different AC line voltages configurations so that it can be operated from line power anywhere in the world The nominal voltage and voltage range of each configuration is shown below The recommended setting for 230 V operation is 240 V Nominal Minimum Maximum 100 V 90 V 106 V 120V 108 V 127 V 220 V 198 V 233 V 240 V 216 V 254 V Verify that the AC line voltage indicator in the fuse drawer window shows the appropriate AC line voltage before turning the instrument on The instrument may be damaged if it is turned on with the wrong voltage selected Instructions for changing the line voltage configuration are given in Paragraph 7 4 3 3 2 Line Fuse and Fuse Holder The line fuse is an important safety feature of the Model 625 If a fuse ever fails it is important to replace it with the value and type indicated
2. OA Ramp Segments Rate 0 0001 A s Display Display Mode Current Voltage Sense Display On Brightness ca ciate D seed ERE 25 Persistent Switch Persistent Switch Mode Disabled AAA Off PSH Current esses 10 mA PSH Delay Time eese 5s Persistent Mode Rate Disabled Persistent Mode Ramp Rate 0 1 A s Keypad Locking A eon Unlocked Lock Code ehe ntt 123 Computer Interface Baud ssec A e 9600 IEEE Address sess 12 IEEE Terminators CR LF Mode cin Local Indicates value is also initialized on power up 4 18 Operation Lake Shore Model 625 Superconducting MPS User s Manual CHAPTER 5 COMPUTER INTERFACE OPERATION 5 0 GENERAL This chapter provides operational instructions for the computer interface for the Lake Shore Model 625 Superconducting Magnet Power Supply Either of the two computer interfaces provided with the Model 625 permit remote operation The first is the IEEE 488 Interface described in Paragraph 5 1 The second is the Serial Interface described in Paragraph 5 2 The two interfaces share a common set of commands detailed in Paragraph 5 3 Only one interface can be used at a time 5 1 IEEE 488 INTERFACE The IEEE 488 Interface is an instrumentation bus with hardw
3. Operation 4 3 Lake Shore Model 625 Superconducting MPS User s Manual 4 4 DISPLAY SETUP The display of the Model 625 is designed so that all of the pertinent operational information is being presented in a logical manner The most important readings either output current and voltage or calculated magnetic field are displayed using large 11 x 15 block characters that can be seen from across the room The remote voltage sense readings can be displayed if they are being utilized or they can be removed from the display altogether 4 4 1 Display Mode The Model 625 is able to display in two modes output current mode or magnetic field mode In output current mode the output current and voltage are displayed using large 11 x 15 block characters In magnet field mode the calculated magnet field is displayed using large 11 x 15 block characters The display mode also changes the way the Output Setting key works In current mode the output setting value will be in units of amps A but in field mode the output setting value will be in units of field either kG or T Refer to Paragraph 4 5 to set the output current To configure the display press Display Setup The first display setup screen appears as a prompt for the display mode Use the A or V key to select the display mode either Current or Field Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and r
4. enable Specifies if the persistent mode ramp rate is to be used when the magnet is in persistent mode PSH heater off 0 Never use persistent mode ramp rate 1 Use persistent mode ramp rate when in persistent mode lt rate gt Specifies the ramp rate to use while in persistent mode 0 0001 99 999 A s Typically the current can be ramped faster when the magnet is in persistent mode since the current change is not seen by the inductance of the magnet This setting will automatically change the ramp rate when the magnet goes into or out of persistent mode Persistent Mode Ramp Rate Parameter Query RATEP term lt enable gt lt rate gt term n n nnnn Refer to command for description Field Output Reading Query RDGF term field term nn nnnnE nn lt field gt Calculated output field reading Field is calculated by multiplying the field constant by the measured current output Use the FLDS command to set the field constant and field constant units G or T Computer Interface Operation 5 41 RDGI Input Returned Format RDGRV Input Returned Format RDGV Input Returned Format RSEG Input Format Remarks RSEG Input Returned Format RSEGS Input Format Remarks RSEGS Lake Shore Model 625 Superconducting MPS User s Manual Current Output Reading Query RDGI term lt current gt term nn nnnn current Actual measured o
5. Dim Dim Dim Dim Dim strReturn As String strHold As String Term As String ZeroCount As Integer strCommand As String frmSerial Show Term Chr 13 amp Chr 10 ZeroCount 0 strReturn strHold If frmSerial MSComml PortOpen True Then End frmSerial MSComml PortOpen False If frmSerial MSComml CommPort 1 frmSerial MSComml Settings 9600 0 7 1 frmSerial MSComml InputLen 1 frmSerial MSComml PortOpen True Do Do DoEvents Loop Until gSend True gSend False strCommand frmSerial txtCommand Text strReturn strCommand UCase strCommand If strCommand EXIT Then End End If frmSerial MSComml Output strCommand amp Term If InStr strCommand lt gt 0 Then End Loop End Sub While ZeroCount lt 20 And strHold lt gt Chr 10 If frmSerial MSComml InBufferCount frmSerial Timerl Enabled True Do DoEvents Main code section Used to return response Temporary character space Terminators Counter used for Timing out Data string sent to instrument Show main window Terminators are lt CR gt lt LF gt Initialize counter Clear return string Clear holding string Close serial port to change settings Example of Comm 1 Example of 9600 Baud Parity Data Stop Read one character at a time Open port Wait loop Give up processor to other events Loop until Send button pressed Set Flag as false Get Command Clear resp
6. 4 11 2 Maximum Compliance Voltage Limit The maximum compliance voltage limits in magnitude the maximum compliance voltage that can be entered To enter a value for the maximum compliance voltage limit continue from the maximum output current limit screen or press Max Settings then Enter until the following display setup screen appears as a prompt for the maximum compliance voltage limit Use the data entry keys to enter the maximum compliance voltage limit value between 0 1000 and 5 0000 V Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence 4 11 3 Maximum Current Ramp Rate The maximum current ramp rate limits the maximum current ramp rate that can be entered If ramp segments are being used this setting will also limit the ramp rate that can be set by a ramp segment Refer to Paragraph 4 12 to setup Ramp Segments To enter a value for the maximum current ramp rate limit continue from the maximum compliance voltage limit screen or press Max Settings then Enter until the following display setup screen appears as a prompt for the maximum current ramp rate limit Use the data entry keys to enter the maximum current ramp rate limit value between 0 0001 and 99 999 A s Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave
7. Quench Parameter Command Input QNCH enable rate term Format n n nnnn term enable Specifies if quench detection is to be used 0 Disabled 1 Enabled lt rate gt Specifies the current step limit for quench detection 0 0100 10 000 A s Remarks When quench detection is enabled a quench will be detected when the output current attempts to change at a rate greater than the current step limit 5 40 Computer Interface Operation QNCH Input Returned Format RATE Input Format Remarks RATE Input Returned Format RATEP Input Format Remarks RATEP Input Returned Format RDGF Input Returned Format Lake Shore Model 625 Superconducting MPS User s Manual Quench Parameter Query QNCH term lt enable gt lt rate gt term n n nnnn Refer to command for description Output Current Ramp Rate Setting Command RATE lt rate gt term n nnnn lt rate gt Specifies the rate at which the current will ramp at when a new output current setting is entered 0 0001 99 999 A s Sets the output current ramp rate This value will be used in both the positive and negative directions Setting value is limited by LIMIT Output Current Ramp Rate Setting Query RATE term lt rate gt term n nnnn Refer to command for description Persistent Mode Ramp Rate Parameter Command RATEP lt enable gt lt rate gt term n n nnnn term
8. To enter a value for the persistent mode ramp rate continue from the persistent mode ramp rate enable screen or press PSH Setup then Enter until the following setup screen appears as a prompt for the persistent mode ramp rate Use the data entry keys to enter the persistent mode ramp rate between 0 0001 and 99 999 A s Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence 4 15 PSH ON OFF The persistent switch heater should be properly set up before attempting to turn it on Refer to Paragraph 4 14 to setup the persistent switch heater The PSH On and PSH Off buttons will not function unless the persistent switch heater is enabled When the PSH is off no current is sourced to the heater and the persistent switch will revert to its superconducting state The magnet is said to be in persistent mode and any changes to the output current of the supply are not reflected in the magnet When the PSH is on the persistent switch is heated and becomes resistive The magnet current can only be changed when the PSH is on To turn on the persistent switch heater press the PSH On key The PSH will begin warming and the PSH On LED will blink The output current of the power supply cannot be changed while the PSH is in transition Once the persistent switch has stabilized as determined by the PSH delay time the PSH will be on and the P
9. 1 mA 0 05 of reading 2 5 readings s display 10 readings s interface Compensated for lead resistance and 25 source resistance Output Voltage at supply terminals Resolution Accuracy Update Rate Remote Voltage at magnet leads Resolution Accuracy Update Rate Input Resistance Connector 100 uV 1 mV 0 05 of reading 2 5 readings s display 5 readings s interface 100 uV 1 mV 0 05 of reading 1 25 readings s 250 kQ Shared 15 pin D sub Persistent Switch Heater Output PSHO Current Range Compliance Voltage minimum Heater Resistance minimum Setting Resolution Accuracy Operation Protection Connector Front Panel Display Type Display Readings Display Settings Display Annunciators LED Annunciators Keypad Type Keypad Functions Interface IEEE 488 2 Interface Features Reading Rate Software Support Serial Interface Electrical Format Baud Rates Reading Rate Connector Output Current Monitor Sensitivity Accuracy Noise Source Impedance Connector 10 mA to 125 mA 12 V or 21 V selectable 100 1 mA 1 mA On Off with lockout delay of 5 s to 100 s Open or shorted heater detection error message if off and on output currents differ BNC 8 line by 40 character graphic vacuum fluorescent display module Output current calculated field T or G output voltage remote voltage sense Output current calculated field compliance voltage ramp rate
10. 5 1 4 4 6 Using Operation Complete OPC and Operation Complete Query OPC The Operation Complete OPC and Operation Complete Query OPC are both used to indicate when pending device operations complete However the commands operate with two distinct methods The OPC command is used in conjunction with bit 0 OPC of the Standard Event Status Register If OPC is sent as the last command in a command sequence bit 0 will be set when the instrument completes the operation that was initiated by the command sequence Additional commands may be sent between the instrument and the bus controller while waiting for the initial pending operation to complete A typical use of this function would be to enable the OPC bit to generate an SRQ and include the OPC command when programming the instrument The bus controller could then be instructed to look for an SRQ allowing additional communication with the instrument while the initial process executes The OPC query has no interaction with bit 0 OPC of the Standard Event Status Register If the OPC query is sent at the end of a command sequence the bus will be held until the instrument completes the operation that was initiated by the command sequence Additional commands except RST should not be sent until the operation is complete as erratic operation will occur Once the sequence is complete a 1 will be placed in the output buffer This function is typically used to signal a completed operat
11. Instrument firmware version main firmware DAC firmware Example LSCLMODEL625 1234567 1 0 1 0 5 34 Computer Interface Operation OPC Input Remarks Lake Shore Model 625 Superconducting MPS User s Manual Operation Complete Command OPC term Used in conjunction with bit 0 OPC of the Standard Event Status Register If sent as the last command in a command sequence bit 0 will be set when the instrument completes the operation that was initiated by the command sequence Refer to Paragraph 5 1 4 4 6 for more information OPC Input Returned Remarks RST Input Remarks SRE Input Format Remarks SRE Input Returned Format STB Input Returned Format Remarks TRG Input Remarks Operation Complete Query OPC term 1 term Has no interaction with bit 0 OPC of the Standard Event Status Register If sent at the end of a command sequence the bus will be held until the instrument completes the operation that was initiated by the command sequence Once the sequence is complete a 1 will be placed in the output buffer Refer to Paragraph 5 1 4 4 6 for more information Reset Instrument Command RST term Sets controller parameters to power up settings Use the DFLT command to set factory defaults Service Request Enable Register Command SRE bit weighting gt term nnn The Service Request Enable Register determines which summary bits of the Status Byte
12. Label3 Name IbIResponse Caption Response Textl Name txtCommand Text lt blank gt Text2 Name txtResponse Text lt blank gt Command1 Name cmdSend Caption Send Default True Forml Name frmIEEE Caption IEEE Interface Program 12 Add code provided in Table 5 5 a In the Code Editor window under the Object dropdown list select General Add the statement Public gSend as Boolean b Double Click on cmdSend Add code segment under Private Sub cmdSend Click as shown in Table 5 5 c Inthe Code Editor window under the Object dropdown list select Form Make sure the Procedure dropdown list is set at Load The Code window should have written the segment of code Private Sub Form Load Add the code to this subroutine as shown in Table 5 5 13 Save the program 14 Run the program The program should resemble the following i IEEE Interface Program Type exit to end program Command Bikel x Response 15 Type in a command or query in the Command box as described in Paragraph 5 1 5 5 16 Press Enter or select the Send button with the mouse to send command 17 Type Exit and press Enter to quit 5 18 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual Table 5 5 Visual Basic IEEE 488 Interface Program Public gSend As Boolean Global used for Send button state Private Sub cmdSend Click gSend True End Sub Routine to handle Se
13. PSS PSH Short PSO PSH Open ess 7 6 TS TATE TE TITO Enable Register Not Not Not Not Not Not pss Pso N ERSTE ERSTE used Used Used Used Used Used Name Figure 5 1 Model 625 Status System Sheet 2 of 2 5 6 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual 5 1 4 1 6 Reading Registers Any register in the status system may be read using the appropriate query command Some registers clear when read others do not Refer to Paragraph 5 1 4 1 7 The response to a query will be a decimal value that corresponds to the binary weighted sum of all bits in the register see Table 5 1 The actual query commands are described later in this section Table 5 1 Binary Weighting of an 8 Bit Register Position B7 B6 B5 B4 B3 B2 Bl BO Decimal 128 64 32 16 8 4 2 1 Weighting 27 2 25 24 23 2 2 20 Example If bits 0 2 and 4 are set a query of the register will return a decimal value of 21 1 4 16 5 1 4 1 7 Programming Registers The only registers that may be programmed by the user are the enable registers All other registers in the status system are read only registers To program an enable register send a decimal value which corresponds to the desired binary weighted sum of all bits in the register see Table 5 1 The actual commands are described later in this section 5 1 4 1 8 Clearing Registers The me
14. Status and errors PSHO on remote compliance limit fault ramping 26 full travel keys Direct access to common operations menu driven setup SH1 AH1 T5 L4 SR1 RL1 PP0 DC1 DT1 C0 E1 To 10 readings s National Instruments LabVIEW driver consult Lake Shore for availability RS 232C 9600 19200 38400 57600 To 10 readings s 9 pin D sub 60A 6V 1 of full scale mV 20 0 Shared 15 pin D sub Introduction Output Voltage Monitor Sensitivity Accuracy Noise Source Impedance Connector Fault Output Type Relay Contact Connector Remote Inhibit Input Type Connector Trigger Input Type Connector General Ambient Temperature Cooling Warm up Line Power Size Weight Approval pending Calibration Schedule Ordering Information Part Number 625 625 DUAL Select a power configuration VAC 100 B VAC 120 B VAC 120 BC VAC 220 C VAC 240 C VAC 220 D Accessories included 6271 6241 6242 6243 6251 6252 Accessories available 6201 6261 6262 6263 CAL 625 CERT CAL 625 DATA Lake Shore Model 625 Superconducting MPS User s Manual 1V 1V 1 of full scale mV 200 Shared 15 pin D sub Relay closed on fault 30 VDC IA Shared 25 pin D sub TTL or contact closure Shared 25 pin D sub TTL or contact closure Shared 25 pin D sub 15 C to 35 C Air cooled with internal 2 speed fan 30 minutes at output current setting 100 120 220 240 VAC 6 10
15. a uses usea ao an 9 PAM cowe Name OPSTE PSHS PSH Stable RAMP Ramp Done COMP Compliance Figure 5 1 Model 625 Status System Sheet 1 of 2 Computer Interface Operation 5 5 Lake Shore Model 625 Superconducting MPS User s Manual enor Siatus 7 6 5 4 3 2 1 9 Condition Register ERST Error Status 7 6 8 4 3 2 9 5 M 505 eee oo 901 Used Used Hardware Errors ERSTR DAC DAC Processor Not Responding OCF Output Control Failure O S eet OOV Output Over Voltage OOC Output Over Current LLV Low Line Voltage TF Temperature Fault enor situs 7 Te T Y 4 Enable Register Not T Not ERSTE ERSTE os s we o 312 Sst 25 1 EN ejes wr Condition Register ERST Error status 7 6 5 4 5 2 6 Event Register ERSTR Name Operational Errors MDC Magnet Discharging through Crowbar QNCH Magnet Quench Detected to RI Remote Inhibit Detected B Sheet TH Temperature High 1 of 2 HLV High Line Voltage EPE External Current Program Error CAL Calibration Error eworsaus 7 6 5 4 3 2 11 Enable Register ERSTE ERSTE Name Emorstaus 7 8 8 4 2 9 rnm eso usa use usea a usa usea ess so Name poy Y Y Y Y v 4 Error status 7 6 8 4 3 2 9 Event Register Not m ERSTR Used Used Used Used Used Used to C Sheet 1 of 2 PSH Errors
16. fuses software power surges lightning and non rechargeable batteries c software interfacing parts or other supplies not furnished by Lake Shore d unauthorized modification or misuse e operation outside of the published specifications f improper site preparation or site maintenance g natural disasters such as flood fire wind or earthquake or h damage during shipment other than original shipment to you if shipped through a Lake Shore carrier This limited warranty does not cover a regularly scheduled or ordinary and expected recalibrations of the Product b accessories to the Product such as probe tips and cables holders wire grease varnish feedthroughs etc c consumables used in conjunction with the Product such as probe tips and cables probe holders sample tails rods and holders ceramic putty for mounting samples Hall sample cards Hall sample enclosures etc or d non Lake Shore branded Products that are integrated with the Product To the extent allowed by applicable law this limited warranty is the only warranty applicable to the Product and replaces all other warranties or conditions express or implied including but not limited to the implied warranties or conditions of merchantability and fitness for a particular purpose Specifically except as provided herein Lake Shore undertakes no responsibility that the products will be fit for any particular purpose for which you may be buying the Pro
17. logically ANDed to the corresponding enable bit of the Service Request Enable Register When a Service Request Enable Register bit is set by the user and the corresponding summary bit is set in the Status Byte the RQS MSS bit of the Status Byte will be set which in turn sets the Service Request hardware line on the bus 5 4 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual Standard Event 7 6 5 4 3 2 1 0 Bit Status Register Not cue exe Not ave Not oec Name ESR EL ed ips d Output Buffer La pi lano gt By A TA rom MERC B Sheet 20f2 Standard Event Status Enable La Naa Bit i Not Not Not Pe rn as oe oe s oe as o amo PON S Pooran je A ee CME Command Error EXE Execution Error WI QYE Query Error OPC Operation Complete Status pala OSSA Bit RQS Generate service request Reset by serial poll D_ L E MSS Read by STB Service Request ET mb Bit SHE RET PESB Name OSB Operation Summary Bit Crore i7 e6 5 4 3 2 t1 o0 et MSS z Minor ROS Status Bit pst Srs ne MAV Sable SOS Bit ov Y v ot 9 d HESB Hardware Errors Summary Bit Operation OESB Operational Errors Summary Bit amp Ee 7 6 5 4 3 2 1 0 Bt PESB PSH Errors Summary Bit Register Not Not Not Not Not OPSTR ee Name Operation Event Enable 7 7 i7zlel5l4 ls 2 1 0 Bit Register Not Not Not Not Not OPSTE
18. noise of the Model 625 make it possible in many situations to run experiments without going into persistent mode This can help to reduce the time necessary to gather data The Model 625 output architecture relies on low noise linear input and output stages The linear circuitry of the Model 625 permits operation with less electrical noise than switch mode superconducting magnet power supplies One key benefit of this architecture is CE compliance to the electromagnetic compatibility EMC directive including the radiated emissions requirement gt N a E 2 c g E 3 o n 3 a B 3 o n e n o Output Programming Nom o x Elapsed time Seconds eo Nr n The Model 625 output currentis programmed 5 A charge of an 8 6 H AMI magnet with a 95 mA s ramp rate internally via the keypad or the computer output current monitor measured at 58 88 Hz rate with a HP interface externally by the analog programming 34401 data multiplied by 10x to obtain output current results input or by the sum of the external and internal settings For the more popular internal programming the Model 625 incorporates a proprietary digital to analog converter DAC that is monotonic over the entire output range and provides a resolution of 0 1 mA The Model 625 generates extremely smooth and continuous ramps with virtually no overshoot The digitally generated constant current ramp rate is variable between 0 1 mA s
19. with EOS on write AT GPIB TNT Plug and Play TT 8 bit EOS Compare 5 Network adapters Secondary Ports COM amp LPT fio EOS Byte e System devices NONE Z 1 0 Timeout 10 pe f y Properties Refresh Remove sec i Advanced JV System Controller OK Cancel Figure 5 8 GPIBO Setting Configuration System Properties General Device Manager Hardware Profiles Performance I View devices by type des National Instruments GPIB Interfaces Properties 2fx General Device Templates m Computer 8 CDROM 4 5 Disk drives y National Instruments GPIB Interfaces H Display adapters 3 Floppy disk controllers Hard disk controllers Device Name E si Keyboard Monitor Mouse BRA National Instruments GPIB Interface ES P 3B Network adapters DEV12 Attributes xi Y Ports COM amp LPT Interface Termination Methods Timeouts c nm sr Bl System devices GPIEO Send ED at end of write hoec s A 10sec m GPIB Address M Terminate Read on EOS Eme Primary v Set EO with EDS on Write sec 12 re Properties Refresh R 8 bit EOS Compare Secondary NONE fi 0 EOS Byte MV Readdress Figure 5 9 DEV 12 Device Template Configuration 5 16 Computer Interface Operation Lake Shore Model 625 Superconducting
20. 20 1 Changing Serial Baud Rate eene nnne nnne nennen nre en trennen nnne 4 17 4 20 2 Changing IEEE 488 Interface ParameterSs i 4 17 4 21 DEFAULT PARAMETER VALUES rcnt rete tede rette tede et pe ct een bla 4 18 5 COMPUTER INTERFACE OPERATION ccsssccsseeesseessseessseeeeseeeeseeseseeeeseesaseeeeneeeeseeesneeeseeesseeenenesneeeeseneseeeeeas 5 1 5 0 GENERAL 30 cece ee RO ARIAL 5 1 5 1 IEEE 488 INTERFACES c Ue YER e elie 5 1 5 1 1 Changing IEEE 488 Interface ParameterSs ii 5 2 5 1 2 Remote Local Op ration 2 nice ano e eon ere Xe ai 5 2 5 1 3 IEEE 488 Command SIFUCtUfe s uec crecer eren deemed en e pe co Ete ec dad 5 2 5 1 3 1 Bus Gontrol Gommiandis rn tee d RU nia ia iaia 5 3 5 1 3 2 Common Commands ae sarai anali iaia 5 3 5 1 3 3 Device Specific COMMANAS eene enne nnne nennen teneret 5 3 5 1 3 4 Message 9Strinigs ee eicere ads 5 3 5 1 4 Status System iip Ana hi er qne Ned tee De E ee 5 4 5 1 4 1 ade sti EE 5 4 5 1 4 2 Status Begisler Sets ete ONE RU REOR De HERE ERR GN US 5 8 5 1 4 3 Error Status Regisler Sets eet e le Pee OM eG ET ira 5 9 5 1 4 4 Status Byte and Service Request SRQ nennen 5 12 ii Table of Contents Lake Shore Model 625 Superconducting MPS User s Manual TABLE OF CONTENTS Continued Chapter Paragraph Title Page 5 1 5 IEEE Interface Example Programs ii 5 15 5 1 5
21. 232 Baud Rate Query BAUD term lt bps gt term n Refer to command for description Factory Defaults Command DFLT 99 term Sets all configuration values to factory defaults and resets the instrument The instrument must be at zero amps for this command to work The 99 is included to prevent accidentally setting the unit to defaults Display Parameter Command DISP lt mode gt lt volt sense gt lt brightness gt term n n n lt mode gt Specifies the display mode 0 Current Field volt sense Specifies if the remote voltage sense reading is displayed 0 Disabled 1 Enabled brightness Specifies display brightness 0 25 1 5096 2 7596 3 100 Display Parameter Query DISP term Returned mode volt sense brightness term Format ERCL nnn Refer to command for definition Error Clear Command Input ERCL term Remarks This command will clear the operational and PSH errors The errors will only be cleared if the error conditions have been removed Hardware errors can never be cleared Refer to Paragraph 5 1 4 3 for a list of error bits 5 36 Computer Interface Operation ERST Input Returned Format Remarks ERSTE Input Format Remarks ERSTE Input Returned Format ERSTR Input Returned Format Remarks FLDS Input Format Remarks FLDS Input Returned Format Lake Shore Model 625
22. 7 RS232 DTE Connector Details tete de eu re t re ere rre neo eee eR dead ee Evene 7 10 7 8 IEEE 488 Rear Panel Connector DetailS i 7 12 C 1 Typical Gryogenic Storage De Wariano ai C 1 LIST OF TABLES Table No Title Page 2 1 Current Capacity and Total Lead LengthSs i 2 4 3 1 Current Capacity and Total Lead LengthS i 3 4 4 1 Default Parameter Values nnum tiere eg Du px ene hai i 4 18 5 1 Binary Weighting of an 8 Bit Register ui 5 7 5 2 Register Clear Methods a eee EUBU On dde salita insalate 5 7 5 3 Programming Example to Generate an SRQ conc nano nc ronca cann narran cnn 5 13 5 4 IEEE 488 Interface Program Control PropettieS eene 5 18 5 5 Visual Basic IEEE 488 Interface Program i 5 19 5 6 Quick Basic IEEE 488 Interface Program iii 5 22 5 7 Serial Interface Specifications i 5 25 5 8 Serial Interface Program Control PropettieS i 5 28 5 9 Visual Basic Serial Interface Program nnne nennen nennen rennen nnne 5 29 5 10 Quick Basic Serial Interface Program sse nennen nennen nennen nnns 5 30 5 11 Command SUMMA 5 eite Lala iaia iii I pas tee Tr ERR E ERN 5 33 7 1 Instrument Hardware Errors ha aee at ai bee ee eel 7 4 7 2 Operational BftO S x ia eee eis ete ee hes dhe a ee ee dad 7 4 B 1 Conversion fr
23. Allows the user to select from a finite list of parameter values During setting selection the A and V keys are used to select a parameter value Enter is used to accept the change and advance to the next parameter Escape will cancel the change to that parameter and return to the normal display Setting selection screens always include the message Select with AW Data Entry Allows the user to enter numeric parameter values using the data entry keys that are printed on the key tops Data entry keys include numbers from 0 to 9 sign and decimal point The labels printed above the keys describe the key function during normal operation When one of the keys is pressed and a data entry sequence is started the keys follow the data entry functions printed on the key tops Once the correct parameter value is entered press Enter to accept the change and advance to next parameter Pressing Escape once will clear the new value and restart the setting sequence Pressing Escape again will return to the normal display Data entry screens always include the message Enter a value for Related setting selection and data entry sequences are often chained together under a single key To skip over a parameter without changing its value press Enter before pressing an arrow or number key To return to the normal display in the middle of a setting sequence press Escape before pressing an arrow or number key Changes entered before Escape is pressed are kept
24. DISPLAY DEFINITION The Model 625 has an 8 line by 40 character vacuum fluorescent VF display capable of showing both text and graphic images This paragraph describes features of the display that appear during normal operation including current measurement voltage measurement and current programming Other display configurations appear during parameter setting and data entry operations These displays are illustrated in their individual operation paragraphs 4 2 1 Output Current Display When the instrument is configured to display in output current the display will look similar to the display shown in Figure 4 1 The output current reading and the output voltage reading are displayed using large 11 x 15 block characters Below that are the instrument setup parameters including output current setting current ramp rate compliance voltage limit and remote voltage sense reading Display setup is described in Paragraph 4 4 Figure 4 1 Model 625 Output Current Display Operation 4 1 Lake Shore Model 625 Superconducting MPS User s Manual 4 2 2 X Magnet Field Display The instrument can be setup to display calculated field See Figure 4 2 This value is calculated using the output current reading and the field constant See Paragraph 4 13 to setup the field constant If the instrument is setup to display in field then only the field reading will be displayed using the large 11 x 15 block characters Other information is sho
25. DOS window It assumes your IEEE 488 GPIB card is installed and operating correctly refer to Paragraph 5 1 5 3 Use the following procedure to develop the Serial Interface Program in Quick Basic Copy c gpib pc Qbasic qbib obj to the QuickBasic directory QB4 2 Change to the QuickBasic directory and type link q qbib obj bqlb4x lib where x 0 for QB4 0 and 5 for QB4 5 This one time only command produces the library file qbib qlb The procedure is found in the National Instruments QuickBasic readme file Readme qb 3 Start QuickBasic Type qb l qbib qlb Start QuickBasic in this way each time the IEEE interface is used to link in the library file 4 Create the IEEE example interface program in QuickBasic Enter the program exactly as presented in Table 5 6 Name the file ieeeexam bas and save 5 Runthe program 6 Typeacommand query as described in Paragraph 5 1 5 5 Type EXIT to quit the program 5 20 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual GPIBO Configuration GPIB PC2 2A Ver 2 1 Select the primary GPIB address by using the left and right arrow keys This address is used to compute the talk and listen addresses which identify the board or device on the GPIB Valid primary addresses range from 0 to 30 00H to 1EH Send EOI at end of Write Adding 32 to the primary address forms the Listen Address LA Assert REN when SC No Adding 64 to
26. MPS User s Manual 5 1 5 2 Visual Basic IEEE 488 Interface Program Setup This IEEE 488 interface program works with Visual Basic 6 0 VB6 on an IBM PC or compatible with a Pentium class processor A Pentium 90 or higher is recommended running Windows 95 or better It assumes your IEEE 488 GPIB card is installed and operating correctly refer to Paragraph 5 1 5 1 Use the following procedure to develop the IEEE 488 Interface Program in Visual Basic Start VB6 Choose Standard EXE and select Open Resize form window to desired size Bow pm or On the Project Menu select Add Module select the Existing tab then navigate to the location on your computer to add the following files Niglobal bas and Vbib 32 bas 5 Addcontrols to form a Add three Label controls to the form b Addtwo TextBox controls to the form c Add one CommandButton control to the form 6 Onthe View Menu select Properties Window 7 Inthe Properties window use the dropdown list to select between the different controls of the current project 10 Set the properties of the controls as defined in Table 5 4 11 Save the program Computer Interface Operation 5 17 Lake Shore Model 625 Superconducting MPS User s Manual Table 5 4 IEEE 488 Interface Program Control Properties Current Name Property New Value Labell Name IbIExitProgram Caption Type exit to end program Label2 Name IblICommand Caption Command
27. Not Not Not Not Not Pss Pso N ERST Used Used Used Used Used Used Name Eor status 7 8 8 4 3 2 1 0 Event Register ERSTR PSH Errors To Bit 0 PESB of Izi o 4 mig t Status Byte Register E aa ee 7 3 3 2 BN See Figure 5 1 nable Register Not Not Not Not Not Not Pss Pso N ERSTE ERSTE used Used Used Used Used Used Name Figure 5 6 PSH Error Status Register Computer Interface Operation 5 11 Lake Shore Model 625 Superconducting MPS User s Manual 5 1 4 4 Status Byte and Service Request SRQ As shown in Figure 5 1 the Status Byte Register receives the summary bits from the two status register sets and the message available summary bit from the output buffer The status byte is used to generate a service request SRQ The selection of summary bits that will generate an SRQ is controlled by the Service Request Enable Register 5 1 4 4 1 Status Byte Register The summary messages from the event registers and output buffer set or clear the summary bits of the Status Byte Register see Figure 5 5 These summary bits are not latched Clearing an event register will clear the corresponding summary bit in the Status Byte Register Reading all messages in the output buffer including any pending queries will clear the message available bit The bits of the Status Byte Register are described as follows Operation Summary OSB Bit 7 Set summ
28. Paragraph Title Page 1 INTRODUCTION cio iii eaa aaa Eana anaana nirean onkaan aansen aoao paN n rea aranana Na 1 1 1 0 GENERAL 2 5 la LL DR PERI DIE ATTS 1 1 1 1 DESCRIPTION cuca ee aa pibe ei Ha Ce eco d e fe iu 1 1 1 2 SPEGIFIGATIONS 2 4 dae ciere TA fee ees 1 4 1 3 SAFETY SUMMARY 5 ni dte etn shee ned ageret e pt n ertt dali 1 7 1 4 SAFETY SYMBOLS 1 eat tin i eae OR ae ie to e ey 1 7 2 JMAGNET SYSTEM DESIGN aeaaaee eeaeee aTe taasen aap ea anale ii 2 1 2 0 GENERAL ELE eta tdt tes cde T te Metres 2 1 2 1 SUPERCONDUCTING MATERIALS i 2 1 2 2 SUPERCONDUCTING MAGNETS i 2 1 2 2 1 Superconducting Magnet Construction i 2 1 2 2 2 Magnet Inductance 2 rai ated tiet pate Doe i e Bea dalle 2 2 2 2 3 Maximum Ramp Hale eet A e igiiur el 2 3 2 2 4 Maximum Magnet G rtenl eie itii TUR ER RE ER HCM EROR OSEE 2 3 2 2 5 Magnet Quench Protection DiOGeS oo Lina 2 3 2 3 PERSISTENT SWITCHES ie ed in Ee e De d cre eleven Shere eel 2 3 2 4 MAGNET CURREN T EEADS 1 tar ie ek sien eta Ri 2 4 2 5 HELIUM DEWARS cnet cce Da edo corni te Dr repe i ea ee Re co rr eee Lei dida ceda 2 4 2 6 MAGNET QUENGLE ione ett eer re ta ttt dote t et 2 5 37 INSTALLATION a 3 1 3 0 GENERAL istiga rent e uENINnEM DNE oath aati coo ERGO IRO B aah lo ai root ilo nia irta 3 1 3 1 INSPECTION AND UNPACKING ii 3 1 3 2 REAR PANEL DEFINIT IQN tore td o ee e ce icc el Pd ini en PED
29. Program in Quick Basic Start the Basic program Enter the program exactly as presented in Table 5 10 Adjust the Com port and Baud rate in the program as necessary Lengthen the TIMEOUT count if necessary Save the program Run the program Type a command query as described in Paragraph 5 2 7 3 90 ou Ov Uv E A rs Type EXIT to quit the program Table 5 10 Quick Basic Serial Interface Program CLS Clear screen PRINT SERIAL COMMUNICATION PROGRAM PRINT TIMEOUT 2000 Read timeout may need more BAUD 9600 TERM CHR 13 CHR 10 Terminators are lt CR gt lt LF gt OPEN COM1 BAUDS 0 7 1 RS FOR RANDOM AS 1 LEN 256 LINE INPUT ENTER COMMAND or EXIT CMD Get command from keyboard CMDS UCASES CMD Change input to upper case IF CMD EXIT THEN CLOSE 1 END Get out on Exit CMD CMDS TERMS PRINT 1 CMDS Send command to instrument IF INSTR CMD lt gt 0 THEN Test for query RS If query read response N 0 Clr return string and count WHILE N lt TIMEOUT AND INSTR RS TERMS 0 Wait for response INS INPUT LOC 1 1 Get one character at a time IF INS THEN N N 1 ELSE N 0 Add 1 to timeout if no chr RSS RSS INS Add next chr to string WEND Get chrs until terminators IF RS THEN See if return string is empty RS MID RS 1 INSTR RS TERMS 1 Strip off terminators PRINT RESPONSE RS Print response to q
30. To disable the reading compensation of the source impedance send CALCOMP 1 over the computer interface To turn on the reading compensation the default setting send CALCOMP 0 over the interface To make the change nonvolatile send the CALSAVE command after setting the compensation or else the previous setting will be used at the next power up There are some magnet systems in which the 25 Q output resistor is not necessary for stable operation Many of the magnets that have a persistent switch have enough resistance for the power supply to operate properly In this case the resistor can be removed and the reading compensation shut off in software Please contact Lake Shore for further information on removing this resistor CAUTION If the 25 Q output resistor is removed and the power supply is operated on a magnet without enough resistance the power supply can go into oscillation possibly quenching and damaging the magnet Please contact Lake Shore before attempting this procedure 7 8 ELECTROSTATIC DISCHARGE Electrostatic Discharge ESD may damage electronic parts assemblies and equipment ESD is a transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field The low energy source that most commonly destroys Electrostatic Discharge Sensitive ESDS devices is the human body which generates and retains static electricity Simply walking across a carpet in l
31. alerts other system components of the fault If the power supply detects an internal hardware fault the fault relay is closed the front panel fault LED is lit and the condition is latched If the power supply detects an operational fault the fault relay will close for 1 second and then open and the front panel LED will blink When two Model 625s are connected in parallel the fault output should be wired to the remote inhibit line of the other supply Refer to Paragraph 3 9 for details on connecting two power supplies in parallel Installation 3 5 Lake Shore Model 625 Superconducting MPS User s Manual 3 6 2 Remote Inhibit The Remote Inhibit connection on the Digital I O connector is an input that instructs the power supply to immediately set the output current to 0 A This input allows an external device to immediately shut off the output current of the supply in case of a failure This input is normally tied to an external quench detection circuit the fault output of a second power supply or an emergency shut down button This function will only set the output current to zero so if the magnet is still charged it will discharge at a rate determined by the compliance voltage limit The Remote Inhibit input is TTL compatible and a logic low will activate it The signal is internally pulled up to allow operation with a simple switch closure Refer to Figure 3 5 5 V 5 V TTL OR y Figure 3 5 Remote Inhibit and Trigger In Operatio
32. before installing the instrument and powering it on to ensure the best possible performance and maintain operator safety For instrument operating instructions refer to Chapter 4 For computer interface installation and operation refer to Chapter 6 NOTE It is recommended that the instrument be powered up and operated with the shorting bar in place before connecting it to a magnet This will allow the user to setup the supply and become comfortable with its operation without risk of damage to the magnet 3 4 INSPECTION AND UNPACKING Inspect shipping containers for external damage before opening them Photograph any container that has significant damage before opening it If there is visible damage to the contents of the container contact the shipping company and Lake Shore immediately preferably within 5 days of receipt of goods Keep all damaged shipping materials and contents until instructed to either return or discard them Open the shipping container and keep the container and shipping materials until all contents have been accounted for Check off each item on the packing list as it is unpacked Instruments themselves may be shipped as several parts The items included with the Model 625 are listed below Contact Lake Shore immediately if there is a shortage of parts or accessories Lake Shore is not responsible for any missing items if not notified within 60 days of shipment Inspect all items for both visible and hidden damage that occurred
33. costs incurred by you arising from the infringement of patents or trademarks or violation or copyrights by the Product THIS WARRANTY IS NOT TRANSFERRABLE This warranty is not transferrable Except to the extent prohibited by applicable law neither Lake Shore nor any of its subsidiaries affiliates or suppliers will be held liable for direct special incidental consequential or other damages including lost profit lost data or downtime costs arising out of the use inability to use or result of use of the product whether based in warranty contract tort or other legal theory regardless whether or not Lake Shore has been advised of the possibility of such damages Purchaser s use of the Product is entirely at Purchaser s risk Some countries states and provinces do not allow the exclusion of liability for incidental or consequential damages so the above limitation may not apply to you Lake Shore Model 625 Superconducting MPS User s Manual 13 This limited warranty gives you specific legal rights and you may also have other rights that vary within or between jurisdictions where the product is purchased and or used Some jurisdictions do not allow limitation in certain warranties and so the above limitations or exclusions of some warranties stated above may not apply to you 14 Except to the extent allowed by applicable law the terms of this limited warranty statement do not exclude restrict or modify the mandatory statutory rights ap
34. during shipment If damage is found contact Lake Shore immediately for instructions on how to file a proper insurance claim Lake Shore products are insured against damage during shipment but a timely claim must be filed before Lake Shore will take further action Procedures vary slightly with shipping companies Keep all shipping materials and damaged contents until instructed to either return or discard them If the instrument must be returned for recalibration replacement or repair a returned goods RA number must be obtained from a factory representative before it is returned The Lake Shore RA procedure is given in Paragraph 7 2 Items Included with Model 625 Superconducting Magnet Power Supply 1 Model 625 Instrument Model 625 User s Manual Front Handles Rear Handles Digital I O Mating Connector Analog I O Mating Connector Output Shorting Bar and Terminal Fasteners Installed on output bus bars Line Power Cord Fuse Pair for Alternative Voltage Rh INN Line Power Cord for Alternative Voltage Included only when purchased with VAC 120 ALL Power Option 3 1 1 Moving and Handling Four handles are provided for ease of moving and handling the Model 625 Always use at least two and if possible four handles when carrying the unit Installation 3 1 Lake Shore Model 625 Superconducting MPS User s Manual 3 2 REAR PANEL DEFINITION This paragraph defines the rear panel of the Model 625 See Figure 3 1 Readers
35. enter a value for the field constant continue from the field constant units screen or press Field Constant then Enter until the following display setup screen appears as a prompt for the field constant value Use the data entry keys to enter the field constant value between 0 00100 and 1 00000 T A or 0 0100 and 10 0000 kG A Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence 4 14 PERSISTENT SWITCH HEATER OUTPUT Some superconducting magnets are constructed with a persistent switch A persistent switch is a length of superconducting wire that shorts across the terminals of the magnet This length of wire can be heated to drive it into a resistive state so that a voltage can be applied across the magnet terminals and the magnet can be charged or discharged When the heater is shut off this section of wire will cool and become superconducting again and the magnet will be in persistent mode At this time the power supply can be ramped to zero current and even removed from the system while the magnet holds its charge The magnet will continue to hold its charge indefinitely unless the cryogen is allowed to boil off to the point where there is insufficient cooling to keep the magnet in its superconducting state 4 10 Operation Lake Shore Model 625 Superconducting MPS User s Manual 4 14 1 Persistent Switch Heater Output Enabl
36. in its side covers Do not block these holes when the instrument is operating Do Not Operate In An Explosive Atmosphere Do not operate the instrument in the presence of flammable gases or fumes Operation of any electrical instrument in such an environment constitutes a definite safety hazard Keep Away From Live Circuits Operating personnel must not remove instrument covers Refer component replacement and internal adjustments to qualified maintenance personnel Do not replace components with power cable connected To avoid injuries always disconnect power and discharge circuits before touching them Do Not Substitute Parts Or Modify Instrument Do not install substitute parts or perform any unauthorized modification to the instrument Return the instrument to an authorized Lake Shore representative for service and repair to ensure that safety features are maintained Cleaning Do not submerge instrument Clean only with a damp cloth and mild detergent Exterior only Moving and Handling Four handles are provided for ease of moving and handling the Model 625 Always use at least two and if possible four handles when carrying the unit 1 4 SAFETY SYMBOLS Direct current power line Equipment protected throughout by double insulation or reinforced insulation equivalent to Class II of Alternating or direct current power line IEC 536 see Annex H Alternating current power line Three phase alternating current power line
37. listing of all the error conditions When an error condition occurs the name of the error is shown in the lower part of the display alternately with Press Status Key for More Info Pressing the Status key will bring up a screen that will show an extended description of the error An example of how the magnet quench error is shown on the main display is given below To enter the error status display press Status while in the main display A screen similar to the one shown below appears This screen will differ depending on the error that is being displayed If there are no errors to report the display will show No errors reported The following example shows the description for the magnet quench error 4 18 EXTERNAL CURRENT PROGRAMMING The output current of the Model 625 can be set internally externally or by the sum of the external and internal settings Normally the current is controlled internally by entering a setting from the front panel using the Output Setting key Refer to Paragraph 4 5 to set the output current When the external program mode is set to External the front panel setting is fixed at 0 A and the output current is set using an external voltage where 1 V 10 A When the external program mode is set to Sum the internal and external settings are summed together to set the output current When using the External or Sum modes care must be taken to insure that the output current does not exce
38. measured 25 NOTE V measurea is from Step 4 of this section Verify Ioutt Lverify 40 008 A 0 015 Set the Model 625 output current to 55 A ramp rate 20 A s nominal Wait 30 seconds Calculate and record Lou Vshunt Rshunt Verify Tou Iverity 0 008 A 0 015 Set the Model 625 output current to 0 A Send CALSAVE to write this calibration to non volatile memory 7 13 3 7 Calibrate Current Reading Gain 1 SOO ON S pr UD BD E e Rh o W N 14 15 16 17 18 Send CALCOMP 0 this is a math computation that takes into account the current that flows through the 25 Q damping resistor that 1s across the output of the Model 625 CALCOMP 0 turns the compensation ON so that the reading reflects only the current going through the load by subtracting the current going through the resistor Send CALG 0 1 To set the output current reading gain constant to 1 Set the Model 625 output current to 60 A Ramp rate 20 A s nominal Wait 30 seconds Measure the actual voltage across the shunt and record V sunt Calculate and record Imeasuredneg VstunRsnunt Get the Model 625 output current reading by front panel or interface and record Treadingneg Set the Model 625 output current to 60 A Ramp rate 20 A s nominal Wait 30 seconds Measure the actual voltage across the shunt and record V shunt Calculate and record Imeasuredpos Vshunt R shunt Get the Model 625
39. measurement resolution The ability of an instrument to resolve a measured quantity For digital instrumentation this is often defined by the analog to digital converter being used A n bit converter can resolve one part in 2 The smallest signal change that can be measured is the full scale input divided by 2 for any given range Resolution should not be confused with accuracy RhFe Rhodium iron Rhodium alloyed with less than one atomic percent iron is used to make the Lake Shore RF family of sensors Rhodium iron is a spin fluctuation alloy which has a significant temperature coefficient of resistance below 20 K where most metals rapidly lose sensitivity root mean square RMS The square root of the time average of the square of a quantity for a periodic quantity the average is taken over one complete cycle Also known as effective value RS 232C Bi directional computer serial interface standard defined by the Electronic Industries Association EIA The interface is single ended and non addressable Glossary of Terminology A 5 Lake Shore Model 625 Superconducting MPS User s Manual Seebeck effect The development of a voltage due to differences in temperature between two junctions of dissimilar metals in the same circuit self heating Heating of a device due to dissipation of power resulting from the excitation applied to the device The output signal from a sensor increases with excitation level but so does the self heating and the
40. memory 1 2 3 4 5 6 7 1 2 3 Get the Model 625 remote voltage sense reading by front panel or interface 4 5 6 7 7 13 3 5 Calibrate External Programming Voltage Reading Zero 1 Short the external current programming input lines pins 3 and 11 of the Analog I O connector 2 Send CALZ 7 0 To set the external programming voltage reading constant to 0 3 Get the Model 625 external programming voltage reading NOTE To get this reading from the Model 625 press and hold the Status key on the front panel until the display goes dark 3 seconds When the key is then released a diagnostics display will be seen The upper right reading REMOTE I is the reading needed for this step Calculate zero offset constant external programming voltage reading Send CALZ 7 zero offset constant Verify the Model 625 external programming voltage reading to be 0 0 0001 V Sio 7 Send CALSAVE to write this calibration to non volatile memory 7 13 3 6 Calibrate Output Current Gain Span This calibration is the most difficult and most important of the procedure It first requires measuring the span of the trim range which changes from unit to unit within 1 2 to determine the trim adjustment range that corresponds to a 100 calibration trim change In other words we adjust the calibration in from 100 to 100 but the size of the calibration trim range changes slightly for each unit W
41. output current reading by front panel or interface and record Treadingpos Calculate gain constant per Equation 3 Equation 3 Verify gain factor to be 1 0 02 Send CALG 0 gain constant Verify the Model 625 output current reading to equal Imeasuredpos 40 008 A Set the Model 625 output current to 0 A Send CALSAVE to write this calibration to non volatile memory Again this method is somewhat lengthy but takes into account the contribution of the damping resistor to the current reading with resistance in the high current cabling even when cable resistance is low It also averages the differences between positive and negative excursions Service 7 17 Lake Shore Model 625 Superconducting MPS User s Manual 7 13 3 8 Calibrate Voltage Reading Gain 1 2 3 4 Di 10 11 12 13 14 15 16 17 Add the larger load resistor in series with the shunt resistor Set the Model 625 output compliance limit to 5 V Send CALG 5 1 To set the output voltage reading gain constant to 1 Set the Model 625 output current to I 0 18 4 5 R load For example if R load 1 Q set the Model 625 output current to 4 68 A Wait 30 seconds Measure the Model 625 actual output voltage at the output terminals and record Vimeasuredneg This voltage must be between 4 0 and 5 0 volts 4 5 V nominal Get the Model 625 output voltage reading by front panel or interface and
42. over one hundred thousand Joules In the case of a magnet quench all of this energy is going to be dumped into the liquid helium within a matter of a few seconds creating a large amount of helium gas Any dewar that is used with a superconducting magnet should have a pressure relief port on the helium reservoir to allow the helium gas to be dissipated in the case of a quench The level of the liquid helium can be monitored by using a liquid helium level sensor installed in the dewar The level of the helium should never be allowed to drop below the top of the magnet while the magnet is in operation Allowing the magnet to become uncovered can cause a quench Also the level of the helium should never be higher than the inlets of the vapor cooled current leads If the inlets are submerged in liquid helium the helium gas can no longer cool the leads and extra heat will be transferred into the helium reservoir increasing the rate of helium boil off 2 6 MAGNET QUENCH A magnet quench occurs when part of the superconducting wire in the magnet becomes normal and has resistance When a section of the magnet becomes resistive it will begin to heat and will cause more of the magnet to become resistive This causes an unstoppable chain reaction that will result in the magnet dissipating all of its energy into heat This can happen if the critical temperature critical current or critical field are exceeded Refer to Paragraph 2 1 for a description of superconduc
43. radiation baffles in the neck region of the dewar These baffles are normally made from copper and are cooled by the escaping helium gas This will help cut down on radiation losses from the room temperature top flange on the insert It will also help to cut down on conductive heat loss being transferred down the neck of the dewar The high current leads used for charging the magnet should be vapor cooled to reduce the amount of heat that is transferred into the helium reservoir Information gathered from Introduction to Laboratory Cryogenics M N Jirmanus Janis Research Company Inc 2 4 Magnet System Design Lake Shore Model 625 Superconducting MPS User s Manual With the magnet submerged in liquid helium it will be at a temperature of 4 2 K at atmospheric pressure Some magnets are rated to work at 2 2 K allowing a larger field to be generated This temperature can be achieved by lowering the pressure over the helium reservoir thereby lowering the boiling point of the helium Some dewars will have a pumping port that can be attached to a vacuum pump to reduce the pressure and lower the temperature but will increase the rate of liquid helium consumption The amount of energy that can be stored in a magnet is given by the equation E LI Typical laboratory magnets have inductances of 10 to 100 Henries and can have maximum currents of 40 to 120 Amps The energy stored in a typical magnet can be anywhere from a few thousand Joules to
44. reete i eden eo teda dd 4 1 4 2 DISPLAY DEFINITION iaia cte afe eoe ide Rr tet n ea 4 1 4 2 1 Output Current Display datada Hiatt ea ded te eet et 4 1 4 2 2 Magnet Field Display cece enin t reete eit tbe Deo tee cca phen dee dpa iet 4 2 4 2 3 Persistent Switch Heater DisplaYy ii 4 2 4 2 4 EED Anrnurnclators O 4 2 Table of Contents Lake Shore Model 625 Superconducting MPS User s Manual TABLE OF CONTENTS Continued Chapter Paragraph Title Page 4 3 KEYPAD DEEINITIQN gola o e tl en D e eer gestr vetet eda 4 2 4 3 1 Key Descriptions eet ERE ede t oe EM ie iis ula e et ends 4 2 4 3 2 General Keypad Operation uci iere ceci edi cte ia i cente un 4 3 4 4 DISPEAY SETUP nin etat eta E ERE ERREUR EBD FURIEH dai 4 4 4 4 1 Display Moder eee AA IRE een Aes 4 4 4 4 2 Display Remote Voltage Sense nennen rennen neret 4 4 4 4 3 Display Brightniess iet eed patet om e Rl Dee i Rr ERE Sos ER Ra cn at 4 5 4 5 SETTING OUTPUT CURRENT atrio de e ER ee ERE e Ee ote 4 5 4 6 CURRENT RAMP RATE ttc fet rre tte e eee a aede ada 4 6 4 7 COMPLIANCE VOLTAGE LIMIT 5 oie re E REEF RE Er IER EO EAE AERA PIS 4 7 4 8 ZERO OUTPUT CURRENT 3 212 creto tiec enr Dee tr Do e ei ene 4 7 4 9 STOP OUTP T GURRENT iR eR inet d ii ED e utu tete ech ca 4 7 4 10 PAUSE OUTPUT CURRENT riii o onc erate ste Ee ala lidia 4 7 4 11 MAXIMUM SETTINGEIMITS coins ca iocur aoa det c eil Re otn reete pe e Fear na 4
45. should be strapped together with heavy gauge copper wire or ground strap Signal leads in communication cables should not be relied on for ground strapping The high current output stage in the Model 625 uses a bridging output technology and is optically isolated from power line ground Optical isolation of the output stage provides noise immunity from power line Earth related ground loops with outside measurement equipment A 100 ohm internal resistor ties the power line ground to the internal output stage common to provide a reference to the output stage in instances where the output is allowed to float This is to prevent electrostatic build up between the isolated sections of the Model 625 If the magnet coil is left ungrounded this is the only path that keeps the common mode voltage of the magnet at or near earth ground In many instances it is expected that one of current output terminals will be attached to power line ground In this instance it is recommended that the negative terminal be attached to power line ground since tying the positive terminal to ground will result in a small current reading error of 30 70 mA Either output terminal can be connected to power line ground without damage The computer interfaces are still referenced to power line ground The Output Voltage Monitor and Output Current Monitor outputs are sourced from the isolated output stage but are electronically balanced and have a common mode voltage limit of 10 V
46. summary bit indicates that an enabled operational error event has occurred PSH Errors Summary PESB Bit 0 Set summary bit indicates that an enabled persistent switch heater error event has occurred 5 1 4 4 2 Service Request Enable Register The Service Request Enable Register is programmed by the user and determines which summary bits of the Status Byte may set bit 6 RQS MSS to generate a Service Request Enable bits are logically ANDed with the corresponding summary bits see Figure 5 5 Whenever a summary bit is set by an event register and its corresponding enable bit is set by the user bit 6 will set to generate a service request The Service Request Enable command SRE programs the Service Request Enable Register and the query command SRE reads it Reading the Service Request Enable Register will not clear it The register may be cleared by the user by sending SRE 0 5 12 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual From Operation Condition Register From Standard Event Status Register From Output Buffer From Error Status Register Hardware From Error Status Register Operational F From Error Status Register PSH Status Byte 6 5 4 3 2 1 0 si RQS Generate service request Reset by serial poll Enable Register Figure 5 7 Status Byte Register and Service Request Enable Register 5 1 4 4 3 Using Service Request SRQ and Se
47. temperature demagnetization when a sample is exposed to an applied field Ha poles are induced on the surface of the sample Some of the returned flux from these poles is inside of the sample This returned flux tends to decrease the net magnetic field strength internal to the sample yielding a true internal field Hin given by Hint Ha DM where M is the volume magnetization and D is the demagnetization factor D is dependent on the sample geometry and orientation with respect to the field deviation The difference between the actual value of a controlled variable and the desired value corresponding to the setpoint differential permeability The slope of a B versus H curve ua dB dH differential susceptibility The slope of a M versus H curve ya dM dH digital controller A feedback control system where the feedback device sensor and control actuator heater are joined by a digital processor In Lake Shore controllers the heater output is maintained as a variable DC current source digital data Pertaining to data in the form of digits or interval quantities Contrast with analog data dimensionless sensitivity Sensitivity of a physical quantity to a stimulus expressed in dimensionless terms The dimensionless temperature sensitivity of a resistance temperature sensor is expressed as Sa T R dR dT which is also equal to the slope of R versus T on a log log plot that is Sa d InR d InT Note that the absolute temperature
48. the operational and PSH errors Hardware errors cannot be cleared Computed Magnetic Field Parameter Command FLDS units constant term n n nnnn lt units gt Specifies the units of the magnetic field constant 0 T A 1 KG A lt constant gt Specifies the magnetic field constant in either T A or kG A depending on units 0 0010 1 0000 T A or 0 0100 10 000 KG A The computed magnetic field is calculated by multiplying the current output reading by the constant The calculated field and the constant are in the units specified Computed Magnetic Field Parameter Query FLDS term lt units gt lt constant gt term n n nnnn Refer to command for description Computer Interface Operation 5 37 IEEE Input Format Example IEEE Input Returned Format KEYST Input Returned Format Remarks LIMIT Input Format Remarks LIMIT Input Returned Format Lake Shore Model 625 Superconducting MPS User s Manual IEEE 488 Interface Parameter Command IEEE terminator EOI enable lt address gt term n n nn lt terminator gt Specifies the terminator Valid entries 0 lt CR gt lt LF gt 1 lt LF gt lt CR gt 2 lt LF gt 3 No terminator must have EOI enabled lt EOI enable gt Sets EOI mode 0 Enabled 1 Disabled lt address gt Specifies the IEEE address 1 30 Address 0 and 31 are reserved IEEE 0 0 4 term After re
49. used in both the positive and negative directions Setting value is limited by LIMIT Output Compliance Voltage Setting Query SETV term lt voltage gt term n nnnn Refer to command for description Stop Output Current Command STOP term This command will stop the output current ramp within two seconds of sending the command To restart the ramp use the SETI command to set a new output current setpoint or the SETF command to set a new output field setpoint Computer Interface Operation 5 43 TRIG Input Format Lake Shore Model 625 Superconducting MPS User s Manual Trigger Output Current Setting Command TRIG lt I value gt term nn nnnn lt I value gt Sets the value in which the output current will ramp to when the instrument is triggered 0 0000 60 1000A Remarks This command only sets up the trigger Use the TRG command or the GET group execute trigger TRIG Input Returned Format XPGM Input Format Example XPGM function to start a trigger over the interface Trigger Output Current Setting Query TRIG term lt I value gt term nn nnnn Refer to command for description External Program Mode Command XPGM lt mode gt term n lt mode gt 0 Internal 1 External 2 Sum XPGM 1 term Places the Model 625 into external program mode where the output current is set by an external voltage External Program Mode Query Input XPGM term R
50. x 10 is four parts per million precision Careful measurement under controlled conditions which can be repeated with similar results See repeatability Also means that small differences can be detected and measured with confidence See resolution prefixes SI prefixes used throughout this manual are as follows Factor Prefix Symbol Factor Prefix Symbol 1024 yotta Y 10 deci d 107 zetta Z 102 centi c 1018 exa E 10 milli m 1015 peta P 10 micro u 10 tera T 10 nano n 10 giga G 10 2 pico p 10 mega M 10 5 femto f 10 kilo k 10718 atto a 10 hecto h 107 zepto z 10 deka da 1074 yocto y probe A long thin body containing a sensing element which can be inserted into a system in order to make measurements Typically the measurement is localized to the region near the tip of the probe proportional integral derivative PID A control function where output is related to the error signal in three ways Proportional gain acts on the instantaneous error as a multiplier Integral reset acts on the area of error with respect to time and can eliminate control offset or droop Derivative rate acts on the rate of change in error to dampen the system reducing overshoot rack mount An instrument is rack mountable when it has permanent or detachable brackets that allow it to be securely mounted in an instrument rack The standard rack mount is 19 inches wide A full rack instrument requires the entire width of the rack Two half rac
51. 1 IEEE 488 Interface Board Installation for Visual Basic Program ii 5 15 5 1 5 2 Visual Basic IEEE 488 Interface Program Setup ii 5 17 5 1 5 3 IEEE 488 Interface Board Installation for Quick Basic Program eene 5 20 5 1 5 4 Quick Basic Program hannah ee dee ied 5 20 5 1 5 5 Program Operation a active a an dues ee ie i rade rt a a 5 23 5 1 6 Tro bleshooting tieniti ime eden oboe gab acu oe epee ae 5 23 5 2 SERIAL INTERFACE OVERVIEW eite tdg tei el n a ete pd 5 24 5 2 1 Changing Batic Rates ttc tine eee ertet irata fe e qr ico ett obe pite 5 24 5 2 2 Physical Gonnectioris riii RCRUM EBEN LR METIRI Ge AER 5 24 5 2 8 Hardware Support 2 3 uc sehelets ret Td e e de ee v TEC a d e eT ae eH YEA lane se EYE de en 5 25 5 2 4 Character Format teen Rc rodada 5 25 5 2 5 Message MOS canonica a ae 5 25 5 2 6 Message Flow Goritrol uiiooito tarot Aue id ts ca eee rr pte pe P pete roni 5 26 5 2 7 Serial Interface Example Programs ii 5 26 5 2 7 1 Visual Basic Serial Interface Program Setup seen 5 27 5 2 7 2 Quick Basic Serial Interface Program Setup sse 5 30 5 2 7 3 ProgramiOperationeics sete citete n ee 5 31 5 2 8 Troubleshooting 5 tet nib ld ei i Pi b thy 5 31 5 3 CGOMMAND SU MMABARBY 2 COE E eG nn a REOS ue pea e dele 5 82 5 3 1 Interface Commands Alphabetical Listing nennen
52. 13 Increase delay between all commands to 50 ms to make sure instrument is not being over loaded Computer Interface Operation 5 23 Lake Shore Model 625 Superconducting MPS User s Manual 5 2 SERIAL INTERFACE OVERVIEW The serial interface used in the Model 625 is commonly referred to as an RS 232C interface RS 232C is a standard of the Electronics Industries Association EIA that describes one of the most common interfaces between computers and electronic equipment The RS 232C standard is quite flexible and allows many different configurations However any two devices claiming RS 232C compatibility cannot necessarily be plugged together without interface setup The remainder of this paragraph briefly describes the key features of a serial interface that are supported by the instrument A customer supplied computer with similarly configured interface port is required to enable communication 5 2 1 Changing Baud Rate To select the Serial Interface Baud Rate press the Computer Interface key The first computer interface screen appears as a prompt for Baud Use the A or W key to select 9600 19200 38400 or 57600 Baud The default is 9600 Baud Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display 5 2 2 Physical Connection The Model 625 has a 9 pin D Subminiature plug on the rear panel for serial communication The origi
53. 228 coden PHTOAD A 6 Glossary of Terminology Lake Shore Model 625 Superconducting MPS User s Manual APPENDIX B UNITS FOR MAGNETIC PROPERTIES Table B 1 Conversion from CGS to SI Units Gaussian Conversion SI amp uantit 7 nti amp CGS emu Factor C Rationalized mks Magnetic flux density Magnetic induction gauss G 104 tesla T Wb n weber Wb volt second Vs ampere A Magnetic Flux maxwell Mx Gecm 108 Magnetic potential difference magnetomotive force gilbert Gb 10 47 Magnetic field strength magnetizing force gt a oersted Oe Gb cm 103 47 z 8 emu cm h 103 107 41 Volume magnetization Volume magnetization Magnetic polarization intensity of magnetization 4 T Wb m A m kg 4n x 107 Wb m kg A m joule per tesla J T 4n x 10 10 Wbemi dimensionless Henry per meter emu cm 4n x 107 H m Wb A m 4n x 10 m kg 4n 2 x 10710 H m kg 4n x 10 m mol Am x 101 Hem mol 4n x 107 H m Wb A m dimensionless emu cm 4n x 104 a E Mass magnetization emu g Magnetic moment emu erg G Magnetic dipole moment emu erg G m Volume susceptibility Mass susceptibility Xp cm g emu g Molar susceptibility Ymol Kmol cm mol emu mol Permeability dimensionless not defined Relative permeability Volume energy density energy product 3 z 2 3 erg cm dimensionless d
54. 5 34 6 OPTIONS AND ACCESSORIES ci aii 6 1 6 0 GENERAL vota dete t dede vt o ar n edes 6 1 6 1 MODELS inea nte ede o ete ee A eee 6 1 6 2 AGGESSORIES e aie i ger tegi De tp rers tee ai ees Ro Pe Dep il 6 1 Kap llide me E 7 1 7 1 CONTACTING LAKE SHORE CRYOTRONICS i 7 1 7 2 RETURNING PRODUCTS TO LAKE SHORE i 7 1 7 8 FUSE DRAWER ess iion BERNER 7 2 7 4 LINE VOLTAGE SELECTION iia zaia ilaele eve eda react dr aee 7 2 7 5 FUSE REPLACEMENT ici i Eat ie dee Het eese 7 3 7 6 ERROR MESSAGES eruat isi gue dec bal ovina te 7 3 7 7 OUTPUT SOURGCE IMPEDANGE 2 iei tr ct eR De pede dete Pie e es 7 5 7 8 ELECTROSTATIC DISGHARGE Stic 2 nein C ENG TO RH ER RE RENE 7 5 7 8 1 Identification of Electrostatic Discharge Sensitive Components i 7 5 7 8 2 Handling Electrostatic Discharge Sensitive Components seen 7 6 7 9 ENCLOSURE BOTTOM REMOVAL AND REPLACEMENT i 7 6 7 10 FIRMWARE REPEAGEMENT tania iaa UR lia olii 7 7 7 11 PSH OUTPUT COMPLIANCE VOLTAGE CONFIGURATION eese 7 7 7 12 CONNECTOR AND CABLE DEFINITIONS i 7 9 7 12 1 Serial Interface Cable Wiring iii 7 11 7 12 2 IEEE 488 Interface Connector eterne Deer eee cie dee dL bd 7 12 7 18 CALIBRATION sonata decia On nell one este rine Re epe betta ee ee 7 13 APPENDIX A GLOSSARY OF TERMINOLOJQGY eeeeeeeeeee
55. 6 bit Windows GPIB applications being used 3 Locate the following files and make note of their location These files will be used during the development process of a Visual Basic program a Niglobal bas b Vbib 32 bas NOTE If the files in Steps 2 and 3 are not installed on your computer they may be copied from your National Instruments setup disks or they may be downloaded from www ni com 4 Configure the GPIB by selecting the System icon in the Windows 98 95 Control Panel located under Settings on the Start Menu Configure the GPIB Settings as shown in Figure 5 1 Configure the DEV12 Device Template as shown in Figure 5 2 Be sure to check the Readdress box Computer Interface Operation 5 15 Lake Shore Model 625 Superconducting MPS User s Manual System Properties 2 x General Device Manager Hardware Profiles Perform lad GPIB TNT Plug and Play Properties KI ES d S General GPIB Settings Resources View devices by type C View devices by col B Computer y AT GPIB TNT Plug and Play CDROM 1 9 Disk drives ISA PrP Serial Number OO4D7FA0 Display adapters 2 2 Floppy disk controllers Interface Name r Termination Methods 3 Hard disk controllers GFIEO M Send EOI at end of Write 3 Keyboard E e Monitor GPIB Address IV Terminate Read on EOS Mouse Primary il E W National Instruments GPIB Interfaces h al M Set EO
56. 7 4 11 1 Maxirium QOutput CUE inen te he AUT ERE ai assai ninna dii rei alia 4 7 4 11 2 Maximum Compliance Voltage Limit ii 4 8 4 11 3 Maximum Current Ramp Rate nennen nennen nenne rerit ner en rerit enne nnne nens 4 8 4 12 RAMP SEGMENTS ssi farla etis ester denen get o De m o m Bre Masses e Ex pete Pr eas am dd 4 9 4 18 FIEEB GONS TANT iiit eet oi ub ER VR LEER Un sod 4 10 4 13 1 Field Gonstant Units ore ai Lal ene iaia 4 10 4 13 2 Field Gonstant alu s et Re m t deii al oi ii 4 10 4 14 PERSISTENT SWITCH HEATER OUTPUT i 4 10 4 14 1 Persistent Switch Heater Output EnNable i 4 11 4 14 2 Persistent Switch Heater Current Setting i 4 11 4 14 3 Persistent Switch Heater Delay eene nennen nnne nennen rese ntes 4 12 4 14 4 Persistent Mode Ramp Rale 5 5 eee ee dete ERR PAIRE AR AER RIERA NOR iii 4 12 4 15 PSELON OEEa ee rettet antenne REB DEI IEEE 4 13 4 16 QUENCH DETEGTIQN 2 82 erre Ie cce en tee ce FEE Dn eese inte th eco eed rede ett aa 4 14 4 16 1 Quench Detection Enable wii tia tenerse ede I e ne leaden ies 4 14 4 16 2 Current Step Limiti piedi lia Bin tenet Ere ur alla 4 14 4 17 ERROR STATUS DISPLAY ees corto e A i te ee Eth e Ff heb er hee dde 4 15 4 18 EXTERNAL CURRENT PROGRAMMING essen nennen nennt nn nennt nnne nnne nnn 4 15 4 19 LOCKING THE KEY PAD coccion I Hen lose eet o eene de 4 16 4 20 INTERFACE PD 4 17 4
57. A control system in which the system outputs are controlled by system inputs only and no account is taken of actual system output pascal Pa The SI unit of pressure equal to 1 N m Equal to 1 45 x 104 psi 1 0197 x 107 kgr cm 7 5 x 10 torr 4 191 x 10 inches of water or 1 x 10 bar A 4 Glossary of Terminology Lake Shore Model 625 Superconducting MPS User s Manual permeability Material parameter which is the ratio of the magnetic induction B to the magnetic field strength H u B H Also see Initial Permeability and Differential Permeability platinum Pt A common temperature sensing material fabricated from pure platinum to make the Lake Shore PT family of resistance temperature sensor elements polynomial fit A mathematical equation used to fit calibration data Polynomials are constructed of finite sums of terms of the form aixi where a is the i fit coefficient and x is some function of the dependent variable positive temperature coefficient PTC Refers to the sign of the temperature sensitivity For example the resistance of a PTC sensor increases with increasing temperature pounds per square inch psi A unit of pressure 1 psi 6 89473 kPa Variations include psi absolute psia measured relative to vacuum zero pressure where one atmosphere pressure equals 14 696 psia and psi gauge psig where gauge measured relative to atmospheric or some other reference pressure ppm Parts per million e g 4
58. Caution High voltages danger of electric shock Background color Earth ground terminal Yellow Symbol and outline Black Protective conductor terminal instrument documentation Background color Yellow Symbol and outline Black Caution or Warning See Frame or chassis terminal On supply Off supply E Fuse O Or ede Introduction 1 7 Lake Shore Model 625 Superconducting MPS User s Manual This Page Intentionally Left Blank 1 8 Introduction Lake Shore Model 625 Superconducting MPS User s Manual CHAPTER 2 MAGNET SYSTEM DESIGN 2 0 GENERAL This chapter provides information on general magnet system design It is intended to give the user insight into superconducting materials superconducting magnets persistent switches dewars and cabling issues For information on how to install the Model 625 please refer to Chapter 3 Instrument operation information is contained in Chapter 4 2 4 SUPERCONDUCTING MATERIALS Superconducting materials have a very special property that when cooled to very low temperatures they become perfect conductors of electricity The transition to the superconducting state happens abruptly as the critical temperature is reached When the material is in its superconducting state it has absolutely zero resistance Such materials have a variety of applications one of which is for the construction of high field magnets The unique properties of superconductors make th
59. FLDS Magnetic Field Parameter Cmd wood SETF Output Field Setting Query 43 FLDS Magnetic Field Parameter Query 37 SETI Output Current Setting Cmd suse 43 IEEE TEEE 488 Interface Parameter Cmd 38 SETI Output Current Setting Query sss 43 IEEE TEEE 488 Interface Parameter Query 38 SETV Output Voltage Setting Cmd sss 43 KEYST Keypad Status Query sse 38 SETV Output Voltage Setting Query sss 43 LIMIT Limit Output Settings Cmd sss 38 STOP Stop Output Current Cmd sss 43 LIMIT Limit Output Settings Query sss 38 TRIG Trigger Output Setting Cmd sss 44 LOCK Keypad Lock Cmd see 38 TRIG Trigger Output Setting Query sss 44 LOCK Keypad Lock Query eene 39 XPGM External Program Mode Cmd 44 MODE IEEE Interface Mode Cmd sss 39 XPGM External Program Mode Query 44 MODE IEEE Interface Mode Query sees 39 Computer Interface Operation 5 33 5 3 1 CLS Input Remarks ESE Input Format Remarks ESE Input Returned Format ESR Input Returned Format Remarks IDN Lake Shore Model 625 Superconducting MPS User s M
60. Firmware version information for the main firmware and the DAC firmware is also displayed during this sequence To clear EEPROM memory or view the firmware versions press and hold the Escape key for 5 seconds The following screen appears to show the main firmware version the DAC processor firmware version and as a prompt for returning the instrument parameters to default values Default parameter values are listed in Table 4 1 Use the A or W key to select Yes for default values and No to continue without changing the parameter values Press Enter to accept the new selection and return to the normal display Press Escape to cancel the new selection and return to the normal display Table 4 1 Default Parameter Values Output Settings Output Current iene 0A Current Ramp Rate 0 01 A s Compliance Voltage Limit 1V Maximum Settings Max Output Current 60 A Max Compliance Voltage Limit 2V Max Ramp Rate sess 1 A s Calculated Field Field Units sseni narena ea Tesla Field Constant 0 1 T A Quench Detection Quench Detection Enabled Current Step Limit 2 Als External Program Mode External Program Mode Internal Ramp Segments Ramp Segment Disabled Ramp Segments Current
61. Paragraph 7 9 7 11 PSH OUTPUT COMPLIANCE VOLTAGE CONFIGURATION The persistent switch heater output maximum compliance voltage is configurable for 15 V or 24 V operation This is configured by changing an internal jumper The default setting is for 24 V operation The actual voltage compliance limit is dependant on load but guaranteed to be at least 12 V or 21 V depending on the setting Use the following procedures to change the PSH output maximum compliance voltage 1 Follow the top of enclosure REMOVAL procedure in Paragraph 7 9 2 Locate the jumper JMP 2 on the main circuit board See Figure 7 3 3 Place the jumper on the correct compliance voltage setting The settings are printed on the circuit board 4 Follow the top of enclosure INSTALLATION procedure in Paragraph 7 9 Service 7 7 Lake Shore Model 625 Superconducting MPS User s Manual U51 Main Firmware EPROM Compliance Voltage U28 DAC Micro controller ea en pe E pm es on 62 333 oo 00 H B ca m C x cab 3 RO 625 PCB bmp Figure 7 3 Location Of Important Internal Components Service Lake Shore Model 625 Superconducting MPS User s Manual 7 12 CONNECTOR AND CABLE DEFINITIONS The ANALOG I O PSH OUTPUT DIGITAL I O and RS 232 DTE and IEEE 488 INTERFACE connectors are defined in Figures 7 4 thru 7 8 ANA LOG I O Analog_Output bmp Pin Name Pin Name 1 Voltage Sense 9 Vo
62. Register Operational Error Status Register and the Persistent Switch Error Register 5 1 4 2 1 Standard Event Status Register Set The Standard Event Status Register reports the following interface related instrument events power on detected command syntax errors command execution errors query errors operation complete Any or all of these events may be reported in the standard event summary bit through the enable register see Figure 5 2 The Standard Event Status Enable command ESE programs the enable register and the query command ESE reads it ESR reads and clears the Standard Event Status Register The used bits of the Standard Event Register are described as follows Power On PON Bit 7 This bit is set to indicate an instrument off on transition Command Error CME Bit 5 This bit is set if a command error has been detected since the last reading This means that the instrument could not interpret the command due to a syntax error an unrecognized header unrecognized terminators or an unsupported command Execution Error EXE Bit 4 This bit is set if an execution error has been detected This occurs when the instrument is instructed to do something not within its capabilities Query Error QYE Bit 2 This bit indicated a query error It occurs rarely and involves loss of data because the output queue is full Operation Complete OPC Bit 0 When OPC is sent this bit will be set when the
63. Return Remove extra spaces and Terminators Do While Right strReturn 1 Chr 10 Or Right strReturn 1 Chr 13 strReturn Left strReturn Len strReturn 1 Loop Else strReturn No Response Send No Response End If frmIEEE txtResponse Text strReturn Put response in text on main form End If Loop End Sub Computer Interface Operation 5 19 Lake Shore Model 625 Superconducting MPS User s Manual 5 1 5 3 IEEE 488 Interface Board Installation for Quick Basic Program This procedure works on an IBM PC or compatible running DOS or in a DOS window This example uses the National Instruments GPIB PCII IIA card 1 o Row Install GPIB PCIV IIA card using National Instruments instructions Install NI 488 2 software for DOS Version 2 1 1 was used for the example Verify that config sys contains the command device gpib pc gpib com Reboot the computer Run IBTEST to test software configuration Do not install the instrument before running IBTEST Run IBCONF to configure the GPIB PCII IIA board and dev 12 Set the EOS byte to OAH and Enable Repeat Addressing to Yes See Figure 5 11 IBCONF modifies gpib com Connect the instrument to the interface board and power up the instrument Verify the address is 12 and terminators are CR LF 5 1 5 4 Quick Basic Program The IEEE 488 interface program in Table 5 6 works with QuickBasic 4 0 4 5 or Qbasic on an IBM PC or compatible running DOS or in a
64. SH On LED will be on solid Refer to Paragraph 4 14 3 to setup the PSH delay time Note that the PSH cannot be turned on or off while the output current is ramping or in compliance To turn off the persistent switch heater press the PSH Off key The PSH will begin cooling and the PSH On LED will blink Once the persistent switch has stablilzed the PSH will be off and the PSH On LED will be off When turning on the PSH it is important that the output current setting of the power supply is equal to the current in the magnet If the currents are not equal when the PSH is turned on there is a possibility that the magnet can quench The Model 625 adds an extra layer of protection to keep this from happening The Model 625 stores the output current setting of the supply when the PSH was turned off last If the output current setting does not match this stored setting when the PSH is being turned on the following message screen will appear To override the lockout and turn on the PSH anyway use the A or V key to select Yes and press Enter This should only be done if the user is sure that the output current of the power supply matches the current in the magnet To cancel this operation use the A or W key to select No and press Enter or press Escape at any time NOTE If the PSH is turned on when the output current setting does not equal the current in the magnet the power supply will ramp the magnet to the output current setting at the co
65. SRQ Service Request Tells the bus controller that the Model 625 needs interface service A Multiline Command asserts a group of signal lines All devices equipped to implement such commands do so simultaneously upon command transmission These commands transmit with the Attention ATN line asserted low The Model 625 recognizes two Multiline commands LLO Local Lockout Prevents the use of instrument front panel controls DCL Device Clear Clears Model 625 interface activity and puts it into a bus idle state Finally Addressed Bus Control Commands are Multiline commands that must include the Model 625 listen address before the instrument responds Only the addressed device responds to these commands The Model 625 recognizes four of the Addressed Bus Control Commands SDC Selective Device Clear The SDC command performs essentially the same function as the DCL command except that only the addressed device responds GTL Go To Local The GTL command is used to remove instruments from the remote mode With some instruments GTL also unlocks front panel controls if they were previously locked out with the LLO command GET Group Execute Trigger The GET command is used to trigger a device to have its operation started either individually or as part of a group of devices SPE Serial Poll Enable and SPD Serial Poll Disable Serial polling accesses the Service Request Status Byte Register This status register cont
66. Superconducting MPS User s Manual Error Status Query ERST term lt hardware errors gt lt operational errors gt lt PSH errors gt term nnn nnn nnn The integers returned represent the sum of the bit weighting of the error bits Refer to Paragraph 5 1 4 3 for a list of error bits Use the ERRCL command to clear the operational and PSH errors Hardware errors cannot be cleared Error Status Enable Command ERSTE hardware errors operational errors PSH errors term nnn nnn nnn Each bit has a bit weighting and represents the enable disable mask of the corresponding error bits in the Error Status Register This determines which status bits can set the corresponding summary bits in the Status Byte Register To enable an error bit send the command ERSTE with the sum of the bit weighting for each desired bit Refer to Paragraph 5 1 4 3 for a list of error bits Error Status Enable Query ERSTE term hardware errors operational errors PSH errors gt term nnn nnn nnn Refer to Paragraph 5 1 4 3 for a list of error bits Error Status Register Query ERSTR term hardware errors operational errors PSH errors term nnn nnn nnn The integers returned represent the sum of the bit weighting of the error bits These error bits are latched when an error condition is detected This register is cleared when it is read Refer to Paragraph 5 1 4 3 for a list of error bits Use the ERRCL command to clear
67. This limit is more than adequate for any equipment that is referenced to power line ground Similarly the External Current Programming and Remote Voltage inputs are differential and allow easy interface to power line grounded equipment 3 9 CONNECTING MULTIPLE UNITS IN PARALLEL Up to two Model 625 s can be connected in parallel to provide up to 120 A of current at a maximum compliance voltage of 5 V When the units are connected they are still operated individually The total amount of current supplied to the load is the sum of the currents that each supply is delivering If both supplies are ramping current at the same time then the total ramp rate is equal to the sum of both the ramp rates as long as neither of the supplies reaches its compliance voltage limit If the compliance voltage limits of the two supplies are not the same then the total compliance voltage is limited to the lower setting of the two supplies To connect two power supplies together the OUTPUT and OUTPUT terminals of one supply should be connected to the OUTPUT and OUTPUT terminals of the other supply respectively Make these leads as short as possible to minimize output potential differences between the two power supplies and use a heavy enough gauge wire to carry at least 60 A Refer to Table 3 1 for wire gauge properties Connect the OUTPUT and OUTPUT terminals of one of the supplies to the load using a heavy enough gauge wire to carry 120 A On the Digital I O conne
68. User s Manual Model 625 Superconducting Magnet Power Supply ako e Gi ca mi x 5 egee E Ee ES EE ES I I I1 1 1 ON II Ci Model 625 Supercon u Lake Shore CRYOTRONICS Lake Shore Cryotronics Inc 575 McCorkle Blvd Westerville Ohio 43082 8888 USA E mail Addresses sales lakeshore com service Olakeshore com Visit Our Website At www lakeshore com Fax 614 891 1392 Telephone 614 891 2243 Methods and apparatus disclosed and described herein have been developed solely on company funds of Lake Shore Cryotronics Inc No government or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary rights of Lake Shore Cryotronics Inc in these developments Methods and apparatus disclosed herein may be subject to U S Patents existing or applied for Lake Shore Cryotronics Inc reserves the right to add improve modify or withdraw functions design modifications or products at any time without notice Lake Shore shall not be liable for errors contained herein or for incidental or consequential damages in connection with furnishing performance or use of this material Revision 1 6 P N 119 037 9 November 2015 Lake Shore Model 625 Superconducting MPS User s Manual 10 11 12 Lake Shore Model 625 Superconducting MPS User s Manual LIMITED WARRANTY STATEMENT WARRANTY PERIOD THREE 3 YEARS Lake Shore w
69. age to inductance where V is the charging voltage L is the magnet inductance and di dt is the rate of change in current The Model 625 can charge a magnet up to a 5 V rate although many magnets are not designed to be charged at that rate For instance a 10 Henry magnet can be charged at a rate of 0 5 A s with a 5 V limit A rate of 0 1 A s is more typical 2 2 Magnet System Design Lake Shore Model 625 Superconducting MPS User s Manual The resistance of the leads must be taken into account when calculating charge rate since a voltage drop across the leads will limit the voltage that can be delivered to the terminals of the magnet This becomes especially important as the charging current rises since the voltage drop across the leads will increase 2 2 3 Maximum Ramp Rate Not only is the rate at which a magnet can be charged limited to the magnet s inductance but it is also limited by the magnet s construction When a magnet is charged or discharged heat is generated in the coils The faster the ramp rate the more heat that will be generated If the heat cannot be conducted out of the magnet fast enough a section of the superconducting windings can go normal and cause a quench The magnet manufacturer should state the maximum ramp rate of the magnet In some magnets the current cannot be changed at the same rate over the entire current range of the magnet These magnets need to be charged at a slower rate as they reach their maximum cur
70. ains important operational information from the unit requesting service The SPD command ends the polling sequence 5 1 3 2 Common Commands Common Commands are addressed commands which create commonalty between instruments on the bus All instruments that comply with the IEEE 488 1987 standard share these commands and their format Common commands all begin with an asterisk They generally relate to bus and instrument status and identification Common query commands end with a question mark Model 625 common commands are detailed in Paragraph 5 3 and summarized in Table 5 8 5 1 3 3 Device Specific Commands Device specific commands are addressed commands The Model 625 supports a variety of device specific commands to program instruments remotely from a digital computer and to transfer measurements to the computer Most device specific commands perform functions also performed from the front panel Model 625 device specific commands are detailed in Paragraph 5 3 and summarized in Table 5 8 5 1 3 4 Message Strings A message string is a group of characters assembled to perform an interface function There are three types of message strings commands queries and responses The computer issues command and query strings through user programs the instrument issues responses Two or more command strings or queries can be chained together in one communication but they must be separated by a semi colon The total communication string
71. and 99 999 A s To ensure a smooth ramp rate the power supply updates the high resolution DAC 28 times per second A low pass filter on the DAC output smoothes the transitions at step changes during ramping Ramping can also be initiated by the trigger input The output compliance voltage of the Model 625 is settable to a value between 0 1 V and 5 V with a 100 pV resolution The voltage is an absolute setting so a 2 V setting will limit the output to greater than 2 0 V and less than 42 0 V Output Readings The Model 625 provides high resolution output readings The output current reading reflects the actual current in the magnet and has a resolution of 0 1 mA The output voltage reading reports the voltage at the output terminals with a resolution of 100 uV A remote voltage reading is also available to more accurately represent the magnet voltage by bypassing voltage drops in the leads connecting the power supply to the magnet All output readings can be prominently displayed on the front panel and read over the computer interface Protection Managing the stored energy in superconducting magnets necessitates several different types of protection The Model 625 continuously monitors the load line voltage and internal circuits for signs of trouble Any change outside of the expected operating limits triggers the supply to bring the output to zero in a fail safe mode When line power is lost the output crowbar SCR will activate and maintain
72. ant to 0 Set the Model 625 output current to 0 A N N Wo 00 Calculate the gain constant per Equation 2 Equation 2 30 Send CALG 10 gain constant This method while somewhat lengthy averages the trim spans between negative and positive settings to split the error between positive and negative operation It also measures the output terminal voltage and subtracts the calculated current through the internal 25 damping resistor from the total ideal span This gain calibration may shift the initial zero calibration for the Current Output DAC slightly It is best to repeat the current zero calibrations at this point 31 Recalibrate Current Output Zero refer to Section 7 13 3 1 32 Recalibrate Current Reading Zero refer to Section 7 13 3 2 7 16 Service Lake Shore Model 625 Superconducting MPS User s Manual Calibrate Output Current Gain Continued NOTE The Model 625 has an internal 25 resistor in parallel with the output terminals 33 34 35 36 37 38 39 40 41 42 43 44 The V measurea 25 factor accounts for the current that is diverted from the external shunt that flows through the internal resistor See Section 7 7 for further details Set the Model 625 output current to 55 A ramp rate 20 A s nominal Wait 30 seconds Measure the actual voltage across the shunt and record V shunt Calculate and record Lout Vsnun Rstunt Calculate and record Iverity 55 V
73. anual Interface Commands Alphabetical Listing Clear Interface Command CLS term Clears the bits in the Status Byte Register and Standard Event Status Register and terminates all pending operations Clears the interface but not the instrument The related instrument command is RST Standard Event Status Enable Register Command ESE bit weighting gt term nnn The Standard Event Status Enable Register determines which bits in the Standard Event Status Register will set the summary bit in the Status Byte This command programs the enable register using a decimal value that corresponds to the binary weighted sum of all bits in the register Refer to Paragraph 5 1 4 2 1 Standard Event Status Enable Register Query ESE term bit weighting gt term nnn Refer to command for description Standard Event Status Register Query ESR term bit weighting nnn Bits in this register correspond to various system events and latch when the event occurs When an event bit is set subsequent events corresponding to that bit are ignored Set bits remain latched until the register is reset by this query or a CLS command Refer to Paragraph 5 1 4 2 1 Identification Query Input IDN term Returned lt manufacturer gt lt model gt lt serial gt lt firmware version term Format aaaa aaaaaaaa aaaaaaa n n n n manufacture Manufacturer ID model Instrument model number serial Serial number firmware version
74. are and programming standards that simplify instrument interfacing The Model 625 IEEE 488 Interface complies with the IEEE 488 2 1987 standard and incorporates its functional electrical and mechanical specifications unless otherwise specified in this manual All instruments on the interface bus perform one or more of the interface functions of TALKER LISTENER or BUS CONTROLLER A TALKER transmits data onto the bus to other devices A LISTENER receives data from other devices through the bus The BUS CONTROLLER designates to the devices on the bus which function to perform The Model 625 performs the functions of TALKER and LISTENER but cannot be a BUS CONTROLLER The BUS CONTROLLER is the digital computer which tells the Model 625 which functions to perform Below are Model 625 IEEE 488 interface capabilities SHl Source handshake capability e RLI Complete remote local capability e DC1 Full device clear capability DTI Complete device trigger capability CO No system controller capability e T5 Basic TALKER serial poll capability talk only unaddressed to talk if addressed to listen L4 Basic LISTENER unaddressed to listen if addressed to talk e SRI Service request capability AH1 Acceptor handshake capability e PPO No parallel poll capability Et Open collector electronics Instruments are connected to the IEEE 488 bus by a 24 conductor connector cable as specified by the standard Refer to Paragraph 7 12 2 Cable
75. are referred to paragraphs that contain installation instructions and connector pin outs for each feature A summary of connector pin outs is provided in Paragraph 7 12 CAUTION Verify that the AC line voltage indicator in the fuse drawer window shows the appropriate AC line voltage before turning he instrument on CAUTION Make rear panel connections with the instrument power off OUTPUT Two bus bars for the magnet cable connections Refer to Paragraph 3 4 for connecting the OUTPUT magnet cables to the instrument 15 pin D subminiature receptacle provides analog monitor outputs as well as analog inputs ANALOGO Refer to Paragraph 3 5 and see Figure 7 4 Line Input Includes the IEC 320 C14 line cord receptacle and line voltage selector with line voltage Assembly indicator and line fuse holder Refer to Paragraph 3 3 DIGITAL I O 25 pin D subminiature receptacle provides connections for digital inputs and outputs Refer to Paragraph 3 6 and see Figure 7 6 PSH OUTPUT BNC receptacle provides connections for the Persistent Switch Heater Refer to Paragraph 3 7 and see Figure 7 5 RS 232 DTE 9 pin D subminiature plug wired in DTE configuration for use with RS 232C serial computer interface Refer to Paragraph 5 2 2 and see Figure 7 7 IEEE 488 IEEE 488 compliant interface connector for use with IEEE 488 parallel computer INTERFACE interface Refer to Paragraph 5 1 and see Figure 7 8 9 0 00
76. arrants that products manufactured by Lake Shore the Product will be free from defects in materials and workmanship for three years from the date of Purchaser s physical receipt of the Product the Warranty Period If Lake Shore receives notice of any such defects during the Warranty Period and the defective Product is shipped freight prepaid back to Lake Shore Lake Shore will at its option either repair or replace the Product if it is so defective without charge for parts service labor or associated customary return shipping cost to the Purchaser Replacement for the Product may be by either new or equivalent in performance to new Replacement or repaired parts or a replaced Product will be warranted for only the unexpired portion of the original warranty or 90 days whichever is greater Lake Shore warrants the Product only if the Product has been sold by an authorized Lake Shore employee sales representative dealer or an authorized Lake Shore original equipment manufacturer OEM The Product may contain remanufactured parts equivalent to new in performance or may have been subject to incidental use when it is originally sold to the Purchaser The Warranty Period begins on the date the Product ships from Lake Shore s plant This limited warranty does not apply to defects in the Product resulting from a improper or inadequate installation unless OT amp V services are performed by Lake Shore maintenance repair or calibration b
77. ary bit indicates that an enabled operation event has occurred Request Service RQS Master Summary Status MSS Bit 6 This bit is set when a summary bit and the summary bits corresponding enable bit in the Service Request Enable Register are set Once set the user may read and clear the bit in two different ways which is why it is referred to as both the RQS and the MSS bit When this bit goes from low to high the Service Request hardware line on the bus is set this is the RQS function of the bit See Paragraph 5 1 4 4 3 In addition the status of the bit may be read with the STB query which returns the binary weighted sum of all bits in the Status Byte this is the MSS function of the bit Performing a serial poll will automatically clear the RQS function but not the MSS function A STB will read the status of the MSS bit along with all of the summary bits but also will not clear it To clear the MSS bit either clear the event register that set the summary bit or disable the summary bit in the Service Request Enable Register Event Summary ESB Bit 5 Set summary bit indicates that an enabled standard event has occurred Message Available MAV Bit 4 Set summary bit indicates that a message is available in the output buffer Bit 3 Not used Hardware Errors Summary HESB Bit 2 Set summary bit indicates that an enabled hardware error event has occurred Operational Errors Summary OESB Bit 1 Set
78. associated temperature measurement error sensitivity The ratio of the response or change induced in the output to a stimulus or change in the input Temperature sensitivity of a resistance temperature detector is expressed as S dR dT setpoint The value selected to be maintained by an automatic controller serial interface A computer interface where information is transferred one bit at a time rather than one byte character at a time as in a parallel interface RS 232C is the most common serial interface SI Syst me International d Unit s See International System of Units stability The ability of an instrument or sensor to maintain a constant output given a constant input strain relief A predetermined amount of slack to relieve tension in component or lead wires Also called stress relief susceptance In electrical terms susceptance is defined as the reciprocal of reactance and the imaginary part of the complex representation of admittance suscept ibility conduct ance susceptibility x Parameter giving an indication of the response of a material to an applied magnetic field The susceptibility is the ratio of the magnetization M to the applied field H y M H In both SI units and cgs units the volume susceptibility is a dimensionless parameter Multiply the cgs susceptibility by 47 to yield the SI susceptibility See also Initial Susceptibility and Differential Susceptibility As in the case of magnetization the sus
79. at if maintained in two straight parallel conductors of infinite length of negligible circular cross section and placed one meter apart in a vacuum would produce between these conductors a force equal to 2 x 1077 newton per meter of length This is one of the base units of the SI ampere turn A MKS unit of magnetomotive force equal to the magnetomotive force around a path linking one turn of a conducting loop carrying a current of one ampere or 1 26 gilberts ampere meter A m The SI unit for magnetic field strength H 1 ampere meter 41 1000 oersted 0 01257 oersted analog controller A feedback control system where there is an unbroken path of analog processing between the feedback device sensor and control actuator heater analog data Data represented in a continuous form as contrasted with digital data having discrete values analog output A voltage output from an instrument that is proportional to its input For example from a digital voltmeter the output voltage is generated by a digital to analog converter so it has a discrete number of voltage levels autotuning In Lake Shore instruments the Autotuning algorithm automatically determines the proper settings for Gain Proportional Reset Integral and Rate Derivative by observing the time response of the system upon changes in setpoint B Symbol for magnetic flux density See Magnetic Flux Density bar Unit of pressure equal to 10 pascal or 0 98697 standard
80. at the instrument be powered up and operated with the shorting bar in place before connecting it to a magnet This will allow the user to setup the supply and become comfortable with its operation without risk of damage to the magnet When the Model 625 is turned on the display shows the Lake Shore logo and the alarm beeper sounds briefly After a few seconds a Checking Hardware message will appear while the instrument does an internal diagnostic and makes sure everything is working before the output is turned on Most of the instrument setup parameter values are retained when power is off with a few exceptions The output current will always be set to 0 A anytime the instrument is powered up The persistent switch heater if enabled will be turned off When the instrument is powered on for the first time parameter values are set to their defaults as listed in Table 4 1 When initialization is complete the instrument will begin its normal reading cycle and current or field readings should appear on the display Any error messages will appear in the bottom of the display Messages listed in Table 7 1 Instrument Hardware Errors are related to the instrument hardware and may require help from Lake Shore service The messages listed in Table 7 2 Operational Errors are related to instrument operation and may be corrected with user intervention The Model 625 should be allowed to warm up for a minimum of 30 minutes to achieve rated accuracy 4 2
81. ation Lake Shore Model 625 Superconducting MPS User s Manual enorstatus 7 6 8 4 3 2 1 6 9 Condition Register Lo voc once RI ma v ee BRL fame ERST Y d Emor status 7 Te T5 T4 T3 T2 7 9 9 manent as ee peo v v eo ere on Operational Errors To Bit 1 OESB of Status Byte Register See Figure 5 1 Ems 7 6 T5 4 3 2 1 o w nable Register Figure 5 5 Operational Error Status Register 5 1 4 3 3 Persistent Switch Heater Error Status Register Set The PSH Error Status Register reports the following PSH error events PSH short PSH open circuit Any or all of these events may be reported in the standard event summary bit through the enable register see Figure 5 2 The PSH Error Status Register is the third value of the three values associated with the Error Status Registers The Error Status Enable command ERSTE programs the enable register and the query command ERSTE reads it ERSTR reads and clears the Error Status Register The used bits of the Error Status Event Register are described as follows PSH Short PSS Bit 1 This bit is set if the persistent switch heater circuitry has detected a short circuit condition This can happen of the heater load falls below 10 O PSH Open PSO Bit 0 This bit is set if the persistent switch heater circuitry has detected an open circuit condition Error Status 7 6 5 4 3 2 1 0 Bit Condition Register Not
82. atmosphere Baud A unit of signaling speed equal to the number of discrete conditions or signal events per second or the reciprocal of the time of the shortest signal element in a character bit A contraction of the term binary digit a unit of information represented by either a zero or a one BNC Bayonet Nut Connector Glossary of Terminology A 1 Lake Shore Model 625 Superconducting MPS User s Manual boiling point The temperature at which a substance in the liquid phase transforms to the gaseous phase commonly refers to the boiling point at sea level and standard atmospheric pressure calibrate To determine by measurement or comparison with a standard the correct value of each scale reading on a meter or other device or the correct value for each setting of a control knob Carbon Glass A temperature sensing material fabricated from a carbon impregnated glass matrix used to make the Lake Shore Carbon Glass Resistor CGR family of sensors Celsius C Scale A temperature scale that registers the freezing point of water as 0 C and the boiling point as 100 C under normal atmospheric pressure Celsius degrees are purely derived units calculated from the Kelvin Thermodynamic Scale Formerly known as centigrade See Temperature for conversions Cernox A Lake Shore resistance temperature detector based on a ceramic oxy nitride resistance material cgs system of units A system in which the basic unit
83. both excitation and measurement of a sensor This method will not reduce the effect of lead resistance on the measurement Underwriters Laboratories UL An independent laboratory that establishes standards for commercial and industrial products unit magnetic pole A pole with a strength such that when it is placed 1 cm away from a like pole the force between the two is 1 dyne volt V The difference of electric potential between two points of a conductor carrying a constant current of one ampere when the power dissipated between these points is equal to one watt volt ampere VA The SI unit of apparent power The volt ampere is the apparent power at the points of entry of a single phase two wire system when the product of the RMS value in amperes of the current by the RMS value in volts of the voltage is equal to one watt W The SI unit of power The watt is the power required to do work at the rate of 1 joule per second References 1 Sybil P Parker Editor McGraw Hill Dictionary of Scientific and Technical Terms Fifth Edition New York McGraw Hill 1994 IBSN 0 07 113584 7 2 Christopher J Booth Editor The New IEEE Standard Dictionary of Electrical and Electronic Terms IEEE Std 100 1992 Fifth Edition New York Institute of Electrical and Electronics Engineers 1993 IBSN 1 55937 240 0 3 Nelson Robert A Guide For Metric Practice Page BG7 8 Physics Today Eleventh Annual Buyer s Guide August 1994 ISSN 0031 9
84. ceipt of the current terminator the instrument uses lt CR gt lt LF gt as the new terminator uses EOI mode and responds to address 4 IEEE 488 Interface Parameter Query IEEE term terminator EOI enable address term n n nn Refer to command for description Keypad Status Query KEYST term lt keypad status gt term n 1 key pressed 0 no key pressed Returns keypad status since the last KEYST KEYST returns 1 after initial power up Limit Output Settings Command LIMIT lt current gt lt voltage gt lt rate gt term nn nnnn n nnnn n nnnn lt current gt Specifies the maximum output current setting allowed 0 60 1000 A lt voltage gt Specifies the maximum compliance voltage setting allowed 0 1000 5 0000 V lt rate gt Specifies the maximum output current ramp rate setting allowed 0 0001 99 999 A s Sets the upper setting limits for output current compliance voltage and output current ramp rate This is a software limit that will limit the settings to these maximum values Limit Output Settings Query LIMIT term lt current gt lt voltage gt lt rate gt term nn nnnn n nnnn n nnnn Refer to command for description LOCK Keyboard Lock Command Input LOCK lt state gt lt code gt term Format n nnn lt state gt 0 Unlock 1 Lock All 2 Lock Limits lt code gt Specifies lock out code Valid entries are 000 999 Remarks Locks out all front pane
85. ceptibility is often seen expressed as a mass susceptibility or a molar susceptibility depending upon how M is expressed temperature scales See Kelvin Scale Celsius Scale and ITS 90 Proper metric usage requires that only Kelvin and degrees Celsius be used However since degrees Fahrenheit is in such common use all three scales are delineated as follows Boiling point of wate 373 15 K 100 C 212 F Triple point of wate 273 16 K Freezing point of water 273 15 K 0 C 32 F Absolute zero OK 273 15 C 459 67 F kelvin Celsius Fahrenheit To convert Kelvin to Celsius subtract 273 15 To convert Celsius to Fahrenheit multiply C by 1 8 then add 32 or F 1 8 x C 32 To convert Fahrenheit to Celsius subtract 32 from F then divide by 1 8 or C CF 32 1 8 temperature coefficient measurement The measurement accuracy of an instrument is affected by changes in ambient temperature The error is specified as an amount of change usually in percent for every one degree change in ambient temperature tesla T The SI unit for magnetic flux density B 1 tesla 10 gauss thermal emf An electromotive force arising from a difference in temperature at two points along a circuit as in the Seebeck effect tolerance The range between allowable maximum and minimum values torr Unit of pressure 1 torr 1 mm of mercury 1 atmosphere 760 torr two lead Measurement technique where one pair of leads is used for
86. cludes an enable register as shown in Figure 5 1 An enable register determines which bits in the corresponding event register will set the summary bit for the register set in the Status Byte The user may write to or read from an enable register Each event register bit is logically ANDed to the corresponding enable bit of the enable register When an enable register bit is set by the user and the corresponding bit is set in the event register the output summary of the register will be set which in turn sets the summary bit of the Status Byte register 5 1 4 1 4 Status Byle Register The Status Byte register typically referred to as simply the Status Byte is a non latching read only register that contains all of the summary bits from the register sets The status of the summary bits are controlled from the register sets as explained above The Status Byte also contains the Request for Service RQS Master Summary Status MSS bit This bit is used to control the Service Request hardware line on the bus and to report if any of the summary bits are set via the STB command The status of the RQS MSS bit is controlled by the summary bits and the Service Request Enable Register 5 1 4 1 5 Service Request Enable Register The Service Request Enable Register determines which summary bits in the Status Byte will set the RQS MSS bit of the Status Byte The user may write to or read from the Service Request Enable Register Each Status Byte summary bit is
87. contact unit Contact with operator s hands provides a sufficient ground for tools that are otherwise electrically isolated 5 Place ESDS devices and assemblies removed from a unit on a conductive work surface or in a conductive container An operator inserting or removing a device or assembly from a container must maintain contact with a conductive portion of the container Use only plastic bags approved for storage of ESD material 6 Do not handle ESDS devices unnecessarily or remove from the packages until actually used or tested 7 9 ENCLOSURE BOTTOM REMOVAL AND REPLACEMENT WARNING To avoid potentially lethal shocks discharge the magnet turn off the power supply and disconnect it from AC power line before performing this procedure Only qualified personnel should perform this procedure REMOVAL 1 Set power switch to Off O and disconnect power cord from rear of unit 2 Turn power supply over to gain access to the bottom panel 3 Use 5 64 hex key to remove the screw that attaches the bottom panel to the front panel 4 Use a Phillips head screwdriver to remove the 7 screws that hold the bottom panel on including the 4 screws that are used to attach the feet 5 Carefully remove the bottom panel from the unit INSTALLATION 1 Carefully place the bottom panel on the unit 2 Use 5 64 hex key to install the screw that attaches the bottom panel to the front panel 3 Attach the 4 feet to the bottom of the unit 4 Use a Phil
88. control of the magnet discharging at a rate of 1 V until it reaches zero Quench detection is necessary to alert the user and to protect the magnet system The Model 625 uses a basic and reliable method for detecting a quench If the current changes at a rate greater than the current step limit set by the operator a quench is detected and the output current is safely set to zero The remote inhibit input allows an external device to immediately set the output current to zero in case of a failure This input is normally tied to an external quench detection circuit the fault output of a second power supply or an emergency shutdown button The fault output is a relay contact that closes when a fault condition occurs The contact closure alerts other system components of the fault 1 2 Introduction Lake Shore Model 625 Superconducting MPS User s Manual Parallel Operation If an application requires more output current than a single Model 625 can provide two supplies can be connected in parallel for 120 A 5 V operation Each unit is programmed for half of the total output current operates independently and retains 0 1 mA resolution at 60 A operation When the units are properly configured either unit can detect a fault protect itself and issue a fault output signaling the other unit to automatically enter the proper protection mode Persistent Switch Heater Output The integrated persistent switch heater output is a controlled DC current so
89. cted and isolated the gases will liquefy when properly cooled A quick comparison between LHe and LN is provided in Table C 1 Table C 1 Comparison of Liquid Helium and Liquid Nitrogen PROPERTY LIQUID HELIUM LIQUID NITROGEN Boiling Point 91 atm in K Thermal Conductivity Gas w em K Latent Heat of Vaporization Btu liter Liquid Density pounds liter C3 0 HANDLING CRYOGENIC STORAGE DEWARS Cryogenic containers dewars must be operated in accordance with manufacturer instructions Safety instructions will also be posted on the side of each dewar Cryogenic dewars must be kept in a well ventilated place where they are protected from the weather and away from any sources of heat A typical cryogenic dewar is shown in Figure C 1 NON MAGNETIC LIQUID HELIUM KEEP UPRIGHT Dewar eps Figure C 1 Typical Cryogenic Storage Dewar Handling LHe and LN2 Lake Shore Model 625 Superconducting MPS User s Manual C4 0 LIQUID HELIUM AND NITROGEN SAFETY PRECAUTIONS Transferring LHe and LN and operation of the storage dewar controls should be in accordance with the manufacturer supplier s instructions During this transfer it is important that all safety precautions written on the storage dewar and recommended by the manufacturer be followed WARNING Liquid helium and liquid nitrogen are potential asphyxiants and can cause rapid suffocation without warning Store and use in area
90. cted to be too high This error can be cleared when the input line voltage is within specified tolerances External Current Program Error The instrument was not allowed to change to external or sum current programming modes because the programming voltage is greater than 0 025 V This error can be cleared when the programming voltage is less than 0 025 V or the instrument is changed to internal current programming mode Calibration Invalid The instrument has either not been calibrated or the calibration data has been corrupted The error can be cleared at any time and the instrument can still be used but there is no guarantee that it is operating within specifications The instrument needs to be recalibrated to correct this error condition PSH Short Detected The persistent switch heater circuitry has detected a short and the heater has been shut off This error can be cleared at any time and will be checked again when the heater is turned back on PSH Open Circuit Detected The persistent switch heater circuitry has detected an open circuit and the heater has been shut off This error can be cleared at any time and will be checked again when the heater is turned back on 7 4 Service Lake Shore Model 625 Superconducting MPS User s Manual 7 OUTPUT SOURCE IMPEDANCE The current output of the Model 625 has a 25 source impedance resulting from a 25 Q resistor across the output terminals This is
91. ctor connect the Fault Output of each supply to the Remote Inhibit of the other supply Be sure to secure the Digital I O connectors to the power supplies with the connector screws When all connections are made power up both supplies at the same time It is possible that one or both of the supplies will power up with a Remote Inhibit fault detected if both supplies are not powered up at the same time If this occurs wait until both units have powered up and then clear the error using the Status key Refer to Paragraph 7 6 for information on clearing errors Lake Shore sells a Dual Supply Interconnect Cable Kit with all of the necessary cables to connect two supplies in parallel Refer to Paragraph 6 2 for ordering accessories Installation 3 7 Lake Shore Model 625 Superconducting MPS User s Manual 20 ANS AT HT PES OC WARNING x MILA eH POU IE OR CO e e RS232 DTE Z CTR RU A A ERAT 3 Dual_625_Rear bmp Figure 3 7 Connecting Two Power Supplies in Parallel 3 8 Installation Lake Shore Model 625 Superconducting MPS User s Manual 3 10 RACK MOUNTING The Model 625 can be installed into a 19 inch rack mount cabinet using the included rack mount hardware and 19 inch rack support rails The power supply comes from the factory with feet installed These feet need to be removed if the supply is going to be rack mounted Be sure to reinstall the screws once the feet are removed Due to the weight of th
92. d to 4 gt 8 CTS in 8 NC SS 7 RTS out 9 NC A __ _ _92 NC NOTE Same as null modem cable design except PC CTS is provided from the Model 625 on DTR Service 7 11 Lake Shore Model 625 Superconducting MPS User s Manual 7 12 2 IEEE 488 Interface Connector Connect to the IEEE 488 Interface connector on the Model 625 rear with cables specified in the IEEE 488 1978 standard document The cable has 24 conductors with an outer shield The connectors are 24 way Amphenol 57 Series or equivalent with piggyback receptacles to allow daisy chaining in multiple device systems The connectors are secured in the receptacles by two captive locking screws with metric threads The total length of cable allowed in a system is 2 meters for each device on the bus or 20 meters maximum The Model 625 can drive a bus of up to 10 devices A connector extender is required to use the IEEE 488 Interface and Relay Terminal Block at the same time Figure 7 8 shows the IEEE 488 Interface connector pin location and signal names as viewed from the Model 625 rear panel IEEE 488 INTERFACE 13 24 1 12 SH1 AH1 T5 L4 SR1 RL1 PPO DC1 DTO COE1 IEEE Connector bmp PIN SYMBOL DESCRIPTION 1 DIO 1 Data Input Output Line 1 2 DIO2 Data Input Output Line 2 3 DIO 3 Data Input Output Line 3 4 DIO4 Data Input Output Line 4 5 EOI End Or Identify 6 DAV Data Valid 7 NRFD Not Ready For Data 8 NDAC Not Data Accepted 9 IFC Interface Cl
93. ducts Any implied warranty is limited in duration to the warranty period No oral or written information or advice given by the Company its Agents or Employees shall create a warranty or in any way increase the scope of this limited warranty Some countries states or provinces do not allow limitations on an implied warranty so the above limitation or exclusion might not apply to you This warranty gives you specific legal rights and you might also have other rights that vary from country to country state to state or province to province Further with regard to the United Nations Convention for International Sale of Goods CISC if CISG is found to apply in relation to this agreement which is specifically disclaimed by Lake Shore then this limited warranty excludes warranties that a the Product is fit for the purpose for which goods of the same description would ordinarily be used b the Product is fit for any particular purpose expressly or impliedly made known to Lake Shore at the time of the conclusion of the contract c the Product is contained or packaged in a manner usual for such goods or in a manner adequate to preserve and protect such goods where it is shipped by someone other than a carrier hired by Lake Shore Lake Shore disclaims any warranties of technological value or of non infringement with respect to the Product and Lake Shore shall have no duty to defend indemnify or hold harmless you from and against any or all damages or
94. e The persistent switch heater should be enabled only if there is an active persistent switch in the magnet system If no persistent switch is being used then the persistent switch heater should be disabled This will remove the persistent switch heater information from the bottom of the display as well as disable the persistent switch heater on and off buttons If a persistent switch is being used then the heater current and delay time should be setup before using the heater To configure the persistent switch heater press PSH Setup The first persistent switch heater setup screen appears as a prompt for the persistent switch heater mode Use the A or Y key to select the persistent switch heater mode either Enable or Disable Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display In order for the persistent switch heater to be disabled the heater must be off If the heater is on warming or cooling then the persistent switch heater mode will not be allowed to change and an error box will pop up explaining why One of two boxes will show up both shown below 4 14 2 Persistent Switch Heater Current Setting The next setting that is available for the persistent switch heater is the heater current This is the current that will be supplied to the heater when the persistent switch heater is on Typically the pe
95. e power supply it is recommended that the supply be mounted at the bottom of the rack For ventilation the back of the rack should be open and a 1U 44 mm high ventilation cover should be mounted on the rack above and below the power supply Use 19 inch rack support rails not included fastened to the front and back of the cabinet to support the weight of the supply CAUTION The front panel rack mount brackets are used to hold the power supply securely to the front of the rack The rack support rails not the front panel brackets must support the weight of the supply Rack Support Rails Ventilation Cover Quantity 2 MPS_Rack_Mount bmp Figure 3 8 Rack Mounting a Model 625 Power Supply Installation 3 9 Lake Shore Model 625 Superconducting MPS User s Manual This Page Intentionally Left Blank 3 10 Installation Lake Shore Model 625 Superconducting MPS User s Manual CHAPTER 4 OPERATION 4 0 GENERAL This chapter provides operating instructions for the features of the Model 625 Superconducting Magnet Power Supply Computer interface instructions are in Chapter 5 4 4 TURNING POWER ON Verify that the AC line voltage indicator in the fuse drawer window shows the appropriate AC line voltage before turning the instrument on The instrument may be damaged if it is turned on with the wrong voltage selected Instructions for checking line voltage selection are given in Paragraph 3 3 1 NOTE It is recommended th
96. e a reading value status report or the present value of a parameter Response data formats are listed along with the associated queries in Paragraph 5 3 The response is sent as soon as possible after the instrument receives the query Typically it takes 10 ms for the instrument to begin the response Some responses take longer 5 2 6 Message Flow Control It is important to remember that the user program is in charge of the serial communication at all times The instrument cannot initiate communication determine which device should be transmitting at a given time or guarantee timing between messages All of this is the responsibility of the user program When issuing commands only the user program should Properly format and transmit the command including terminators as one string Guarantee that no other communication is started for 50 ms after the last character is transmitted Notinitiate communication more than 20 times per second When issuing queries or queries and commands together the user program should Properly format and transmit the query including terminators as one string Prepare to receive a response immediately e Receive the entire response from the instrument including the terminators Guarantee that no other communication is started during the response or for 50 ms after it completes Notinitiate communication more than 20 times per second Failure to follow these simple rules will result in inabilit
97. e first measure the span of the calibration trim range and then measure the full span of the instrument with the calibration trim set to 0 We have adopted the use of as the unit name for the trim calibration since it corresponds to only the percent of trim range and not the full span of the instrument The 55 A set point for calibration is chosen because the maximum trim range at 60 A forces the current past the 61 A internal analog limit and therefore creates significant error Yet another source of lesser error is the 25 Q parallel damping resistor that is part of the output circuitry of the Model 625 While at a 0 volt output this resistance contributes no error but when there is voltage created by the current this error becomes significant Even though small wiring resistance may allow the voltage across the output terminals of the Model 625 to reach 0 5 V or so at 55 A depending upon length This reduces the measured shunt current by 0 5 V 25 Q or 0 020 A and therefore must be considered during the calibration The shunt resistor remains connected to the output terminals for this procedure Service 7 15 Lake Shore Model 625 Superconducting MPS User s Manual Calibrate Output Current Gain Continued Send CALG 10 0 To set the output current gain trim constant to 0 Set the Model 625 output current to 55 A ramp rate 20 A s nominal Wait 30 seconds for settling Measure the Model 625 actual output voltage at the output te
98. e not saved permanently until the CALSAVE command is issued If a mistake is made in the calibration process turn the instrument power off and on again before CALSAVE is issued to restore the old calibration constants Once CALSAVE is issued old values cannot be retrieved from the instrument If calibration coefficients are left at default or are outside of the normal calibration range the following error message will appear in the instrument display when the instrument is turned on Instrument Uncalibrated This error message must be bypassed to allow calibration of the instrument Press both Enter and Escape keys simultaneously to bypass the error message Operation in this state is possible but at least one calibration is known to be out of proper range and measurement is likely to be erroneous Simple communications program examples are shown in Sections 5 2 7 1 and 5 2 7 2 Some time should be spent becoming familiar with the calibration commands before beginning a calibration Although the calibration factors are sent to the Model 625 over the computer interface this procedure is written to obtain the Model 625 readings solely by visual observation of the front panel Service 7 13 Lake Shore Model 625 Superconducting MPS User s Manual 7 13 2 Calibration Equipment 1 Shunt Resistor The output current of the Model 625 must be measured externally as the primary reference for calibration When current is measured it is the resul
99. ear 10 SRQ Service Request 11 ATN Attention 12 SHIELD Cable Shield 13 DIOS Data Input Output Line 5 14 DIO6 Data Input Output Line 6 15 DIO7 Data Input Output Line 7 16 DIO8 Data Input Output Line 8 17 REN Remote Enable 18 GND6 Ground Wire Twisted pair with DAV 19 GND7 Ground Wire Twisted pair with NRFD 20 GND8 Ground Wire Twisted pair with NDAC 21 GND9 Ground Wire Twisted pair with IFC 22 GNDIO Ground Wire Twisted pair with SRQ 23 GND11 Ground Wire Twisted pair with ATN 24 GND Logic Ground Figure 7 8 IEEE 488 Rear Panel Connector Details 7 12 Service Lake Shore Model 625 Superconducting MPS User s Manual 7 13 CALIBRATION Lake Shore maintains a fully automated calibration fixture for the Model 625 that measures existing performance of the unit and then recalibrates the using NIST traceable resistance and voltage standards In addition non calibration features are verified for proper operation by a full battery of extensive tests Although this testing is very complete it requires the return of the Model 625 to Lake Shore to perform the recalibration In some instances however it may be necessary to recalibrate the Model 625 in the field Calibration information for the following operating parameters is provided Output Current Output Current Reading e Output Voltage Reading Remote Voltage Reading External Programming Voltage The
100. easured PSH output voltage within 20 0005 V 11 Send CALSAVE to write this calibration to non volatile memory 12 Turn off the PSH output 7 13 4 Calibration Specific Interface Commands The following interface commands are only used during calibration and are in addition to those listed in Chapter 5 CALG Gain Calibration Constant Command Input CALG type lt value gt term Format nn nnnnnnn input Specifies the item to calibrate Valid entries are 0 Output Current Reading 1 Bias A Reading 2 Bias B Reading 3 CM Voltage Reading 4 Out Control Reading 5 Output Voltage Reading 6 Remote Voltage Reading 7 External Programming Voltage 8 Temperature 9 Raw Supply Voltage 10 Actual Output Current lt value gt Gain calibration constant value Remarks Items marked with a are for internal diagnostic use only and should always be set to a value of 1 default Service 7 19 Lake Shore Model 625 Superconducting MPS User s Manual Calibration Specific Interface Commands Continued CALG Gain Calibration Constant Query Input CALG lt type gt term Format nn lt type gt 1 10 Returned lt value gt term Format nnnnnnn Refer to command for description CALSAVE Calibration Save Command Input CALSAVE term Remarks Saves all CALZ and CALG calibration constants in non volatile memory CALZ Zero Offset Calibration Constant Command Input CALZ lt t
101. ection and return to the normal display 5 1 2 Remote Local Operation Normal operations from the keypad are referred to as Local operations The Model 625 can also be configured for Remote operations via the IEEE 488 interface or the Remote key The Local key will take the instrument out of Remote operation and place it in Local operation During Remote operations the Remote LED annunciator will be illuminated and operations from the keypad will be disabled 5 1 3 IEEE 488 Command Structure The Model 625 supports several command types These commands are divided into three groups 1 Bus Control Refer to Paragraph 5 1 3 1 a Universal 1 Uniline 2 Multiline b Addressed Bus Control Common Refer to Paragraph 5 1 3 2 3 Device Specific Refer to Paragraph 5 1 3 3 Message Strings Refer to Paragraph 5 1 3 4 5 2 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual 5 1 3 1 Bus Control Commands A Universal Command addresses all devices on the bus Universal Commands include Uniline and Multiline Commands A Uniline Command Message asserts only a single signal line The Model 625 recognizes two of these messages from the BUS CONTROLLER Remote REN and Interface Clear IFC The Model 625 sends one Uniline Command Service Request SRQ REN Remote Puts the Model 625 into remote mode IFC Interface Clear Stops current operation on the bus
102. ed the maximum current for the magnet The software maximum setting limits cannot limit the output current that is set when using the External or Sum modes A 40 Hz low pass filter limits the bandwidth of the external current programming input The bandwidth of the output is also limited by the compliance voltage and the inductance of the magnet See Paragraph 2 2 2 for a description of the relationship between voltage and inductance To configure the external current program mode press External Program The following setup screen appears as a prompt for the external current program mode Operation 4 15 Lake Shore Model 625 Superconducting MPS User s Manual Use the A or Y key to select the external current program mode Internal External or Sum Press Enter to accept the new selection and return to the normal display Press Escape to cancel the new selection and return to the normal display To avoid discontinuities in the output current the external current programming mode cannot be changed if the programming voltage is not zero or the front panel current setting is not zero If the external current program mode is going to be kept from changing an error box will pop up explaining why the new setting is going to be ignored These error boxes are shown below 4 19 LOCKING THE KEYPAD The keypad lock feature prevents accidental changes to parameter values When the keypad is locked parameter values
103. ede e 3 2 3 3 LNE INPUT ASSEMBLY iit ibt tiere eid rd eme ee ae d 3 3 3 3 1 Line Voltage Ten Eireren cemere od ne br bte ce qa Eae Ce RE Er ete chert eaa e Rx 3 3 3 3 2 Line F se ard Fuse Holder edat ttt er ett ert dre pr eem Aa e Rx 3 3 3 3 3 POWel Gold eee ei Ibi Alea reni cl ide ORNERMERUNIBEA BENI 3 3 3 3 4 PoWelSWIICHI i Ue eden anu euin dee ne iie eerie te eie er 3 4 3 4 MAGNET CABEE CONNEGTIONS 4 roit atten toe cnn a a tic 3 4 3 5 ANALOG INPUT OUTPUT CONNECTIONS i 3 4 3 5 1 External Current Programming 2 n il eei b E e t eo De db tete ate 3 4 3 5 2 Remote Voltage Sense eee ERU MEAE TUBE Ne TO RR REEL REESE 3 5 3 5 3 Output Current and Voltage Monitors ii 3 5 3 6 DIGITAL INPUT OUTPUT CONNECTIONS nennen nennt nnns enr nnns ennt enne 3 5 3 6 1 Fault QUIDUE etie ftr RR pene pts e a LE e eade etel 3 5 3 6 2 Remote Inhlbit uote edt lr iii 3 6 3 6 3 TOO Mica aa dos ale ta A ls E E 3 6 3 7 PERSISTENT SWITCH HEATER OUTPUT i 3 6 3 7 1 Heater Output Connection 1 in Dei ed ea 3 6 3 7 2 Heater Output Cabling 2 2 2 1 iren loe bara 3 6 3 8 INSTRUMENT GROUNDING AND ISOLATION sess nnn nnne nennen 3 7 3 9 CONNECTING MULTIPLE UNITS IN PARALLEL nennen nennen nennen nnns 3 7 3 10 RACK MOUNTING 2e e GT On ee UB MIRO 3 9 4 OPERATION ini ai 4 1 4 0 GENERAL 2 45 5 tct ea Ri 4 1 4 1 T RNING POWER ON 5
104. egative temperature coefficient NTC Refers to the sign of the temperature sensitivity For example the resistance of a NTC sensor decreases with increasing temperature National Institute of Standards and Technology NIST Government agency located in Gaithersburg Maryland and Boulder Colorado that defines measurement standards in the United States noise electrical Unwanted electrical signals that produce undesirable effects in circuits of control systems in which they occur normalized sensitivity For resistors signal sensitivity dR dT is geometry dependent i e dR dT scales directly with R consequently very often this sensitivity is normalized by dividing by the measured resistance to give a sensitivity st in percent change per Kelvin sr 100 R dR dT K where T is the temp in Kelvin and R is the resistance in ohms normally closed N C A term used for switches and relay contacts Provides a closed circuit when actuator is in the free unenergized position normally open N O A term used for switches and relay contacts Provides an open circuit when actuator is in the free unenergized position oersted Oe The cgs unit for the magnetic field strength H 1 oersted 10341 ampere meter 79 58 ampere meter ohm Q The SI unit of resistance and of impedance The ohm is the resistance of a conductor such that a constant current of one ampere in it produces a voltage of one volt between its ends open loop
105. ely detect a short circuit Refer to Paragraph 4 14 to setup the persistent switch heater PSH OUTPUT Heater Output bmp Figure 3 6 Persistent Switch Heater Output Connector 3 7 1 Heater Output Connection BNC receptacle provides connections for the persistent switch heater output Signal is carried on the center conductor and heater common is on the outer conductor The heater output has a maximum voltage of 24 V and can source 125 mA Mating connector not included 3 7 2 Heater Output Cabling Coaxial cable is recommended for the heater output outside of the test dewar The center conductor should be large enough to carry the maximum 125 mA current to prevent accidental burn out of the conductor 3 6 Installation Lake Shore Model 625 Superconducting MPS User s Manual 3 8 INSTRUMENT GROUNDING AND ISOLATION Chassis grounded circuits should have a low impedance path to Earth ground for both performance and safety This is achieved by using a 3 conductor power cord in a properly grounded outlet All instrumentation that is connected to the analog outputs or computer interface or use Earth ground as measurement common should have similar low impedance to the same ground Good grounding of all chassis in a group of instruments prevents voltage differences between their chassis usually at line frequency from inducing noise on the measurement If good quality Earth ground is not available the chassis of line powered instruments
106. em ideal for use in high field magnets Since a superconductor has no resistance it requires no voltage to maintain a current through it Magnet grade superconductors also have a very high current density allowing a relatively small wire to carry a large amount of current that can be used to generate large magnetic fields There are three properties that determine if a material is in its superconducting state The first property is critical temperature A superconductor needs to be cooled in order to transition to a superconducting state This temperature is called its critical temperature Most materials need to be cooled with liquid helium in order to reach their critical temperatures although some ceramics have shown to have a critical temperature as high as 125 K which would be suitable for nitrogen cooling The second property is critical current density A superconducting wire can only carry a certain amount of current in its superconducting state The current density of a typical superconducting wire made from niobium titanium is on the order of 10 A m about three orders of magnitude greater than normal house wiring If the critical current density is exceeded the wire will return to its normal resistive state The last property is critical field A superconductor will return to its normal resistive state if it is exposed to a magnetic field larger than its critical field Superconducting wire such as niobium titanium and niobium tin have crit
107. enable a status bit send the command OPSTE with the sum of the bit weighting for each desired bit Refer to Paragraph 5 1 4 2 2 for a list of operational status bits Operational Status Enable Query OPSTE term bit weighting term nnn Refer to Paragraph 5 1 4 2 2 for a list of operational status bits Operational Status Register Query OPSTR term bit weighting term nnn The integers returned represent the sum of the bit weighting of the operational status bits These status bits are latched when the condition is detected This register is cleared when it is read Refer to Paragraph 5 1 4 2 2 for a list of operational status bits Computer Interface Operation 5 39 PSH Input Format Remarks PSH Input Returned Format PSHIS Input Returned Format PSHS Input Format Remarks PSHS Input Returned Format QNCH Lake Shore Model 625 Superconducting MPS User s Manual Persistent Switch Heater Command PSH lt mode gt term n term lt mode gt Specifies if the persistent switch heater is to be turned on or off 0 Heater off 1 Heater on 99 Heater on overriding output current setting check This command turns the current to the persistent switch on or off The switch needs to be enabled and setup using the PSHS command If the output current is not the same as the current setting when the PSH was turned off last the PSH will not be turned on unless t
108. eneeenn eene ennt nennen nnn annnm s sten Nanananananana nanana nissa A 1 APPENDIX B UNITS FOR MAGNETIC PROPERTIES rreceie iii B 1 APPENDIX C HANDLING LIQUID HELIUM AND NITROGEN eene enne nnne nannten natn nn nnn C 1 Gi 0 OENERAL REESE er t Bust blade AL nete ida Fred ot DRE C 1 C2 0 PROPERTIES urtare let ete ett edic eer e teles seem at ipae ctn C 1 C3 0 HANDLING CRYOGENIC STORAGE DEWARS i C 1 C4 0 LIQUID HELIUM AND NITROGEN SAFETY PRECAUTIONS esee ennemi C 2 C5 0 RECOMMENDED FIRST AID cuina D Lei ee i citet ene Eee eee dde ee edere ad C 2 Table of Contents Lake Shore Model 625 Superconducting MPS User s Manual LIST OF ILLUSTRATIONS Figure No Title Page 1 1 Model 625 Front Panel ut ee tee Ea UL eed dee 1 3 2 1 Typical Superconducting Magnet iii 2 2 2 2 Cutaway of a Typical Helium Dewar Magnet and Insert 2 2 3 1 Model 625 Rear Panel ier nginten e Se a ete Deb e equi edo m e a 3 2 3 2 Line Input Assembly EU re Pr ean cl tbi be editis 3 3 3 3 Model 625 Analog Input Output Connector i 3 4 3 4 Model 625 Digital Input Output Connector i 3 5 3 5 Remote Inhibit and Trigger In Operation nennen nennen nens 3 6 3 6 Persistent Switch Heater Output Connector i 3 6 3 7 Connecting Two Power Supplies In Parallel i 3 8 3 8 Rack Mou
109. eration 4 5 Lake Shore Model 625 Superconducting MPS User s Manual The output current setting is not allowed to change while the persistent switch heater is warming or cooling The amount of time it takes for the PSH to warm or cool is system dependant and can be setup under the PSH Setup key Refer to Paragraph 4 14 to setup the persistent switch heater The output current setting is not allowed to change if the instrument is setup so that the output current is programmed solely by an external voltage Refer to Paragraph 4 18 to setup the external program mode The output current setting is not allowed to change if the current ramp rate is greater than the current step limit and quench detection is on The current step limit is a parameter of quench detection If the current were allowed to change at arate greater than the current step limit then a quench would be falsely detected Refer to Paragraph 4 16 to setup quench detection As stated above the current ramp rate cannot exceed the current step limit used for quench detection To insure that the ramp rate will never accidentally exceed the current step limit either by entering a ramp rate from the front panel or by having the ramp segments function set a new ramp rate the maximum ramp rate must be less than the current step limit Refer to Paragraph 4 11 to setup maximum settings 4 6 CURRENT RAMP RATE The output current of the Model 625 wil
110. eturn to the normal display 4 4 2 Display Remote Voltage Sense The Model 625 has the ability to display a remote voltage sense reading This connection is available on the rear panel of the instrument See Paragraph 3 5 2 for information on how to connect the remote voltage sense leads These leads are normally used to monitor the voltage at the terminals of the magnet The remote voltage sense reading can be displayed or hidden if the remote voltage sense leads are not being used Note that the remote voltage sense leads will always be read only the display function can be turned on or off The sense voltage cannot be used as the compliance voltage To change the remote voltage sense display continue from the display mode screen or press Display Setup then Enter until the following display setup screen appears as a prompt for the remote voltage sense display Use the A or V key to select the remote voltage sense display either On or Off Press Enter to accept the new selection and continue to other display features Press Escape to cancel the new selection and return to the normal display 4 4 Operation Lake Shore Model 625 Superconducting MPS User s Manual 4 4 3 Display Brightness The vacuum fluorescent VF display on the Model 625 has four brightness settings between 100 and 25 that can be changed from the front panel The brightness setting changes the entire VF display but does not affect the LED annunciators to t
111. eturned lt mode gt term Format n Refer to command for description 5 44 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual CHAPTER 6 OPTIONS AND ACCESSORIES 6 0 GENERAL This chapter provides information on power line configurations and accessories available for the Model 625 MPS 6 1 MODELS The list of Model 625 part numbers is provided as follows Part Number Description 625 Superconducting Magnet Power Supply 625 DUAL Two Model 625s and one 6263 dual supply interconnect cable kit Line Power Configurations The instrument is configured at the factory for customer selected line power as follows Other country line cords are available consult Lake Shore 100V US NEMA 5 15 120V US NEMA 5 15 220V EU CEE 7 7 240V EU CEE 7 7 240V UK BS 1363 240V Swiss SEV 1011 220V China GB 1002 NIAJ B amp B UJN 6 2 ACCESSORIES INCLUDED Part Number 6271 Model 625 Superconducting MPS User s Manual 6241 Two front handles 6242 Two rear handles protectors 6243 Output shorting bar and terminal fasteners 6251 25 pin D sub mating connector digital I O 6252 15 pin D sub mating connector analog I O Calibration Certificate 6 3 ACCESSORIES AVAILABLE Part Number 6201 IEEE 488 Cable Kit 1 meter 3 foot IEEE 488 GPIB computer interface cable assembly 6261 Magnet Cable Kit 3 me
112. eys separated into 4 groups on the instrument front panel The group of keys farthest to the left control the persistent switch heater the center group combines instrument setup and data entry the keys farthest to the right control the computer interface mode of the instrument and the keys at the bottom control the output current 4 3 1 Key Descriptions Output Setting Sets the output current Refer to Paragraph 4 5 Ramp Rate Sets the output current ramp rate Refer to Paragraph 4 6 Voltage Limit Sets the compliance voltage limit for the output Refer to Paragraph 4 7 Zero Output Ramps the current to 0 A at the programmed ramp rate Refer to Paragraph 4 8 Stop Output Stops the output at the present value during a ramp Refer to Paragraph 4 9 Pause Output Pauses the output during a ramp Press again to continue ramp Refer to Paragraph 4 10 4 2 Operation PSH Setup Quench Detect Display Setup Escape Field Constant External Program Computer Interface Ramp Segments Max Settings Status Enter 0 9 A Up Y Down PSH On PSH Off Remote Local Lake Shore Model 625 Superconducting MPS User s Manual Setup persistent switch heater enable current delay time and persistent mode ramp rate Refer to Paragraph 4 14 Setup quench detect enable and current step limit Refer to Paragraph 4 16 Setup display mode and brightness Refer to Paragraph 4 4 Exits from parameter setting sequence without changing the pa
113. gain constant to be 1 0 02 Send CALG 6 gain constant Verify the Model 625 remote voltage sense reading to match the measured PSH output voltage within 0 0005 V Send CALSAVE to write this calibration to non volatile memory Turn off the PSH output 7 18 Service Lake Shore Model 625 Superconducting MPS User s Manual 7 13 3 10 Calibrate External Current Programming Voltage Reading Gain 1 Connect the PSH output in parallel with the DVM a 100 Q resistor as a load and the external current programming input lines Send CALG 7 1 To set the external programming voltage reading gain constant to 1 3 Set the PSH switch heater to 50 mA and turn on the PSH output to provide a 5 0 VDC level to be measured by the external current programming input lines Measure the PSH output voltage and record V measured 5 Verify V measured 5 0 0 1 V 6 Get the Model 625 external programming voltage reading and record V reading NOTE To get this reading from the Model 625 press and hold the Status key on the front panel until the display goes dark 3 seconds When the key is then released a diagnostics display will be seen The upper right reading REMOTE I is the reading needed for this step 7 Calculate the gain constant per Equation 6 Equation 6 8 Verify the gain constant to be 1 0 02 9 Send CALG 7 constant 10 Verify the Model 625 external programming voltage reading to match the m
114. gnetometer extraction magnetometer SQUID magnetometer etc The exact technical definition relates to the torque exerted on a magnetized sample when placed in a magnetic field Note that the moment is a total attribute of a sample and alone does not necessarily supply sufficient information in understanding material properties A small highly magnetic sample can have exactly the same moment as a larger weakly magnetic sample see Magnetization Measured in SI units as A m and in cgs units as emu 1 emu 10 A m magnetic units Units used in measuring magnetic quantities Includes ampere turn gauss gilbert line of force maxwell oersted and unit magnetic pole magnetization M This is a material specific property defined as the magnetic moment m per unit volume V M m V Measured in SI units as A m and in cgs units as emu cm 1 emu cm 10 A m Since the mass of a sample is generally much easier to determine than the volume magnetization is often alternately expressed as a mass magnetization defined as the moment per unit mass microcontroller A microcomputer microprocessor or other equipment used for precise process control in data handling communication and manufacturing MKSA System of Units A system in which the basic units are the meter kilogram and second and the ampere is a derived unit defined by assigning the magnitude 4x x 107 to the rationalized magnetic constant sometimes called the permeability of space n
115. groups Instrument hardware errors are related to the instruments internal circuits When one of these errors occurs the output crowbar SCR will be thrown the Fault LED will be lit and there will be no way to clear the error unless power is cycled If one of these error messages persist after power is cycled the instrument requires repair Instrument hardware errors are listed in Table 7 1 Operational errors are related to instrument operation and do not necessarily indicate a hardware problem When one of theses errors occurs the Fault LED will be blinking and the error condition can be cleared once the fault condition has been removed Operational errors are listed in Table 7 2 Table 7 1 Instrument Hardware Errors DAC Processor not Responding The processor that controls the output DAC is not responding or is responding incorrectly The output crowbar SCR has been thrown to prevent damage to the magnet or the supply Output Control Failure One of the internally monitored voltages is beyond an acceptable range on power up The output crowbar SCR has been thrown to prevent damage to the magnet or the supply Output Voltage gt Compliance Setting The output voltage is greater than the compliance voltage setting indicating a problem with the compliance voltage circuitry The output crowbar SCR has been thrown to prevent damage to the magnet or the supply Output Over Current The output current exceeded 62 amps The out
116. h provides a listing of the IEEE 488 and Serial Interface Commands A summary of all the commands is provided in Table 5 11 All the commands are detailed in Paragraph 5 3 1 which is presented in alphabetical order Sample Command Format SETI Output Current Setting Command Input SETI lt current gt term Format nn nnnn lt current gt Specifies the output current setting 0 0000 60 1000A Remarks Sets the current value that the output will ramp to at the present ramp rate Setting value is limited by LIMIT Sample Query Format SETI Output Current Setting Query Input SETI term Returned lt current gt term Format nn nnnn Refer to command for description Key Begins common interface command Required to identify queries aa String of alpha numeric characters nn String of number characters that may include a decimal point nnn nnnEtnn Number represented in scientific notation format term Terminator characters a Indicated a parameter field many are command specific lt state gt Parameter field with only On Off states NOTE Any number being represented in scientific notation may also be entered as a string of number characters If the number is only represented as a string of number characters it cannot be entered in scientific notation The following example shows two different ways of sending the same command Refer to the individual command descriptions for further details SETF 2 0E 03
117. he PSH 99 command was issued Persistent Switch Heater Query PSH term lt mode gt term n lt mode gt Specifies the current mode of the persistent switch heater 0 Heater off 1 Heater on 2 Heater warming 3 Heater cooling Last Current Setting When PSH Was Turned Off Query PSHIS term current term nn nnnn lt current gt Specifies the output current of the power supply when the persistent switch heater was turned off last The PSH will not be allowed to turn on unless this current is equal to the present output current or the heater is turned on using the PSH 99 command If 99 9999 is returned then the output current when the PSH was turned off last is unknown Persistent Switch Heater Parameter Command PSHS lt enable gt lt current gt lt delay gt term n nnn nnn term enable Specifies if there is a persistent switch in the system 0 Disabled no PSH 1 Enabled current Specifies the current needed to turn on the persistent switch heater 10 125 mA lt delay gt Specifies the time needed to turn the persistent switch heater on or off 5 100 s If there is no persistent switch heater in the system then the switch should be disabled This command does not turn on the current to the persistent switch That command is PSH Persistent Switch Heater Parameter Query PSHS term enable current delay term n nnn nnn Refer to command for description
118. he right of the display Continuous use of the instrument at 100 brightness will reduce the operating life of the display and brightness of 25 is recommended for most applications To change display brightness continue from the remote voltage sense display screen or press Display Setup then Enter until the following display setup screen appears as a prompt for display brightness Use the A or W key to select brightness 25 50 75 or 100 Press Enter to accept the new selection and return to the normal display Press Escape to cancel the new selection and return to the normal display 4 5 SETTING OUTPUT CURRENT The main purpose of the Model 625 Superconducting Power Supply is to supply a very precise and stable current to a highly inductive load Before setting output current make sure that the instrument is properly setup for the magnet system that is being used This includes setting up the maximum output current maximum compliance voltage limit maximum ramp rate quench detection and PSH parameters When a new output current setting is entered the supply will ramp from the current setting to the new setting at the current ramp rate unless limited by the compliance voltage The Ramping LED will be lit while the output current setting is ramping When the output current setting is entered it will be limited in magnitude by the maximum current setting Refer to Paragraph 4 11 to setup the maximum settings To change the ou
119. hnical Commission IEEE Institute of Electrical and Electronics Engineers IEEE 488 An instrumentation bus with hardware and programming standards designed to simplify instrument interfacing The addressable parallel bus specification is defined by the IEEE initial permeability The permeability determined at H 0 and B 0 initial susceptibility The susceptibility determined at H 0 and M 0 infrared IR For practical purposes any radiant energy within the wavelength range 770 to 10 nanometers is considered infrared energy The full range is usually divided into three sub ranges near IR far IR and sub millimeter interchangeability Ability to exchange one sensor or device with another of the same type without a significant change in output or response international system of units SI A universal coherent system of units in which the following seven units are considered basic meter kilogram second ampere Kelvin mole and candela The International System of Units or Syst me International d Unit s SD was promulgated in 1960 by the Eleventh General Conference on Weights and Measures For definition spelling and protocols see Reference 3 for a short convenient guide interpolation table A table listing the output and sensitivity of a sensor at regular or defined points which may be different from the points at which calibration data was taken intrinsic coercivity The magnetic field strength H required to red
120. ical fields in excess of 10 T and 20 T respectively Elemental superconductors such as lead have very low critical fields in this case 0 08 T and are not suited for creating superconducting magnets All three of these properties are related to one another For instance a superconducting wire is able to carry more current and withstand a higher magnetic field as it is cooled to a lower temperature In the case of niobium titanium a common superconducting wire the critical temperature is 9 3 K but at that temperature both the critical field and critical current density are both zero At a temperature of 6 K the critical field increases to approximately 7 T and at 4 K it is approximately 11 T 2 2 SUPERCONDUCTING MAGNETS Superconducting magnets are wound from many turns of superconducting wire They are used to generate magnetic fields that are larger than can be achieved with permanent magnets or electromagnets or when field stability is important They can also be more economical to run than electromagnets since the power needed to maintain the charge is minimal 2 2 1 Superconducting Magnet Construction The magnetic field B that can be generated by a solenoid is given by the equation B polIn 1 where po is the permeability of air I is the current in the wire n is the number of turns and l is the length of the solenoid Most superconducting magnets are wound using a conductor made from many fine strands of niobium titanium NbTi or niobi
121. ickBasic 4 0 4 5 on an IBM PC or compatible The example requires a properly configured National Instruments GPIB PC2 card The REM INCLUDE statement is necessary along with a correct path to the file QBDECL BAS CONFIG SYS must call GPIB COM created by IBCONF EXE prior to running Basic There must be QBIB QBL library in the QuickBasic Directory and QuickBasic must start with a link to it All instrument settings are assumed to be defaults Address 12 Terminators lt CR gt lt LF gt and EOI active To use type an instrument command or query at the prompt The computer transmits to the instrument and displays any response If no query is sent the instrument responds to the last query received Type EXIT to exit the program REM INCLUDE c gpib pc qbasic qbdecl bas CLS PRINT IEEE 488 COMMUNICATION PROGRAM PRINT CALL IBFIND dev12 DEV12 TERMS CHR 13 CHR 10 INS SPACES 2000 LINE INPUT ENTER COMMAND or EXIT CMD CMD UCASES CMD IF CMD EXIT THEN END CMD CMD TERMS CALL IBWRT DEV12 CMDS CALL IBRD DEV12 INS ENDTEST INSTR INS CHR 13 IF ENDTEST gt 0 THEN INS MID IN 1 ENDTEST 1 PRINT RESPONSE INS ELSE PRINT NO RESPONSE END IF GOTO LOOP2 Link to IEEE calls Clear screen Open communication at address 12 Terminators are lt CR gt lt LF gt Clear for return string Get command from keyboard Change input to upper case Get out on Exi
122. ides high precision low noise safety and convenience Precision in magnetic measurements is typically defined as smooth continuous operation with high setting resolution and low drift Achieving these goals while driving a challenging load such as a superconducting magnet requires a unique solution The Model 625 delivers up to 60 A at a nominal compliance voltage of 5 V with the supply acting as either a source or a sink in true 4 quadrant operation Its current source output architecture with analog control enables both smooth operation and low drift A careful blending of analog and digital circuits provides high setting resolution of 0 1 mA and flexible output programming Lake Shore chose linear input and output power stages for the moderate 300 W output of the Model 625 Linear operation eliminates the radiated radio frequency RF noise associated with switching power supplies allowing the Model 625 to reduce the overall noise in its output and the noise radiated into surrounding electronics Safety should never be an afterthought when combining stored energy and liquid cryogens in a superconducting magnet system The Model 625 incorporates a variety of hardware and firmware protection features to ensure the safety of the magnet and supply For improved operator safety the power supply was also designed for compliance with the safety requirements of the CE mark including both the low voltage and the electromagnetic compatibility EMC direc
123. ill be returned Incorrectly spelled commands and queries are ignored Commands and queries should have a space separating the command and associated parameters Leading zeros and zeros following a decimal point are not needed in a command string but are sent in response to a query A leading is not required but a leading is required 5 2 8 Troubleshooting New Installation 1 Check instrument Baud rate 2 Make sure transmit TD signal line from the instrument is routed to receive RD on the computer and vice versa Use a null modem adapter if not Always send terminators Send entire message string at one time including terminators Many terminal emulation programs do not Send only one simple command at a time until communication is established ORARI Be sure to spell commands correctly and use proper syntax Old Installation No Longer Working 7 Power instrument off then on again to see if it is a soft failure 8 Power computer off then on again to see if communication port is locked up 9 Verify that Baud rate has not been changed on the instrument during a memory reset 10 Check all cable connections Intermittent Lockups 11 Check cable connections and length 12 Increase delay between all commands to 100 ms to make sure instrument is not being over loaded Computer Interface Operation 5 31 Lake Shore Model 625 Superconducting MPS User s Manual 5 3 COMMAND SUMMARY This paragrap
124. imensionless Magnetic dipole moment Meses ves Pemeability pu E j e Demagnetization factor D N Demagnetization factor NOTES a Gaussian units and cgs emu are the same for magnetic properties The defining relation is B H 47M b Multiply a number in Gaussian units by C to convert it to SI e g 1 G x 10 T G 10 T c SI Syst me International d Unit s has been adopted by the National Bureau of Standards Where two conversion factors are given the upper one is recognized under or consistent with SI and is based on the definition B uo H M where to uo 4x x 107H m The lower one is not recognized under SI and is based on the definition B poH J where the symbol I is often used in place of J 1 gauss 10 gamma y Both oersted and gauss are expressed as cm ges in terms of base units A m was often expressed as ampere turn per meter when used for magnetic field strength Magnetic moment per unit volume Fa mo a The designation emu is not a unit Recognized under SI even though based on the definition B poH J See footnote c j u Wpozl all in SL uris equal to Gaussian p k Be Hand uM H have SI units J m M H and B H 4x have Gaussian units erg cm R B Goldfarb and F R Fickett U S Department of Commerce National Bureau of Standards Bolder Colorado 80303 March 1985 NBS Special Publication 696 For sale by the Superintendent of Documents U S Gover
125. in Paragraph 1 2 for input and source impedances Pin Name Pin Name 1 Voltage Sense 9 Voltage Sense 2 NC 10 NC 3 Current Program 11 Current Program 4 NC 12 NC 5 Voltage Monitor 13 Voltage Monitor 6 NC 14 NC 7 Current Monitor 15 Current Monitor 8 NC Figure 3 3 Model 625 Analog Input Output Connector 3 5 1 External Current Programming The output current can be programmed externally using an analog voltage This programming voltage can also be summed with the internal current setting Refer to Paragraph 4 18 to change the external program mode The external current programming input is a differential input with a sensitivity of 1 V 10 A and an input impedance of gt 50 KQ The programming voltage is limited internally to approximately 6 1 V but care must be taken to insure that maximum current capability of the magnet is never exceeded 3 4 Installation Lake Shore Model 625 Superconducting MPS User s Manual 3 5 2 Remote Voltage Sense The Model 625 provides a connection for remote voltage sense leads This connection is normally used to measure the voltage at the magnet allowing a more accurate reading of magnet voltage by eliminating voltage drops in the leads connecting the power supply to the magnet This voltage reading can be displayed on the front panel or read over the computer interface Refer to Paragraph 4 4 2 to configure the display to show the remote voltage sense read
126. in Kelvin must be used in these expressions drift instrument An undesired but relatively slow change in output over a period of time with a fixed reference input Note Drift is usually expressed in percent of the maximum rated value of the variable being measured electromagnet A device in which a magnetic field is generated as the result of electrical current passing through a helical conducting coil It can be configured as an iron free solenoid in which the field is produced along the axis of the coil or an iron cored structure in which the field is produced in an air gap between pole faces The coil can be water cooled copper or aluminum or superconductive electrostatic discharge ESD A transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field error Any discrepancy between a computed observed or measured quantity and the true specified or theoretically correct value or condition excitation Either an AC or DC input to a sensor used to produce an output signal Common excitations include constant current constant voltage or constant power Fahrenheit F Scale A temperature scale that registers the freezing point of water as 32 F and the boiling point as 212 F under normal atmospheric pressure See Temperature for conversions feedback control system A system in which the value of some output quantity is controlled by feeding bac
127. inal packing material should be retained for reshipment If not available a minimum of three inches of shock adsorbent packing material should be placed snugly on all sides of the instrument in a sturdy corrugated cardboard box The RA number should be included in the mailing label or written prominently on the outside of the box A copy of the customer contact information and RA number should be included inside the box Consult Lake Shore with questions regarding shipping and packing instructions Service 7 1 Lake Shore Model 625 Superconducting MPS User s Manual 7 3 FUSE DRAWER The Model 625 may be configured for two basic AC power configurations 100 or 120 VAC and 220 or 240 VAC Each configuration requires the appropriate fuses and fuse holder Units produced for use with 100 or 120 VAC have two 0 25 x 1 25 inch time delay fuses and the appropriate fuse holder installed Units produced for use with 220 or 240 VAC have two 5 x 20 mm time delay fuses and the appropriate fuse holder installed To change the AC power configuration from the factory setting use the fuses and fuse holder in the connector kit shipped with the instrument The Model 625 requires two good fuses of the same rating to operate safely Refer to Paragraph 7 5 for details 5x20 mm drawer dark 0 25x1 25 drawer light 625 Fuse Open bmp Figure 7 1 Fuse Drawer 7 4 LINE VOLTAGE SELECTION Use the following procedure to change the instrument line
128. inear regulation with digital setting and analog control 60 A 5 V maximum nominal both source and sink 300 W 0 H to 100 H 4 mA RMS at 60 A 0 007 into 1 mQ load significantly reduced into a reactive load or at lower current Dominated by line frequency and its harmonics 15 ppm of full scale C 15 ppm 6 line change 250 1 mA h after warm up 10 mA 24 h typical dominated by temperature coefficient and line regulation Output optically isolated from chassis to prevent ground loops 2 units can be paralleled for 120 A 5 V operation Quench Line Loss Low Line Voltage High Line Voltage Output Over Voltage Output Over Current Over Temperature Remote Inhibit on critical error conditions magnet discharges at 1 V nominal 0 1 mA 20 bit 600 ms for 1 step to within 0 1 mA into a resistive load 10 mA 0 05 of setting Keypad computer interface Current setting limit 0 1 mA s to 99 999 A s compliance limited 27 7 increments s 5 Keypad computer interface trigger input Ramp rate limit 6V 60A Analog 10 mA 1 of setting 40 Hz 2 pole low pass filter 10 Hz pass band compliance limited gt 50 KQ Voltage program through rear panel Shared 15 pin D sub Internally clamped at 6 1V 0 1 V to 5 0 V 100 uV 10 mV 1 of setting Introduction Readings Output Current Resolution Accuracy Update Rate Compensation Lake Shore Model 625 Superconducting MPS User s Manual 0 1 mA
129. ing The remote voltage sense connection is a differential input capable of reading 5 V and an input impedance of gt 50 kO 3 5 3 Output Current and Voltage Monitors The output current and output voltage of the power supply can be monitored externally using the monitor output connections on the Analog I O connector Each output is a buffered differential analog voltage representation of the signal being monitored The current monitor has a sensitivity of 1 V 10 A and the voltage monitor has a sensitivity of 1 V 1V Both outputs have a source impedance of 20 Q 3 6 DIGITAL INPUT OUTPUT CONNECTIONS The Digital I O connector provides connections to digital control signals Two of these connections Remote Inhibit and Trigger In are inputs used to control the state of the power supply The Fault Out is an output that is used to signal error conditions T DIGITALVO 5 1 13 Digital IO bmp Pin Name Pin Name 1 Fault Out Common 14 Fault Out 2 NC 15 NC 3 Remote Inhibit Common 16 Remote Inhibit 4 NC 17 NC 5 Trigger Out Common not used 18 Trigger Out not used 6 NC 19 NC 7 Trigger In Common 20 Trigger In 8 NC 21 NC 9 NC 22 NC 10 NC 23 NC 11 NC 24 NC 12 NC 25 NC 13 NC Figure 3 4 Model 625 Digital Input Output Connector 3 6 1 Fault Output The fault output is a relay contact closure that closes to indicate a fault condition The relay contact is rated at 30 VDC at 1 A The contact closure
130. ing in in 9 Ring in in Figure 7 7 RS232 DTE Connector Details 7 10 Service Lake Shore Model 625 Superconducting MPS User s Manual 7 12 1 Serial Interface Cable Wiring The following are suggested cable wiring diagrams for connecting the Model 625 Serial Interface to various Customer Personal Computers PCs Model 625 to PC Serial Interface PC with DE 9P Model 625 DE 9P Standard Null Modem Cable DE 9S to DE 9S PC DE 9P 5 GND A 5 GND 2 RD in AH _3 TD out 3 TD out TOTTTT__T_ _ _ _ __ 2 RD in 4 DTR out 6 DSR in 6 DSR in LO O s DTR out 1 NC ae CVVNV cMOFB VSS SIZE 7 RTS out 7 DTR tied to 4 8 CTS in 8 NC 1 DCD in Model 625 to PC Serial Interface PC with DB 25P Model 625 DE 9P Standard Null Modem Cable DE 9S to DB 25S PC DB 25P 5 GND AX 2 7 GND 2 RD in 1 2 TD out 3 TD out 3 RD in 1 NC ESTE 4 RTS out 7 DTR tied to 4 gt 5 CTS in 8 NC i 8 DCD in 6 DSR in 20 DTR out 4 DTR out 6 DSR in Model 625 to PC Interface using Null Modem Adapter Model 625 DE 9P Null Modem Adapter PC DE 9P 5 GND gt 5 GND 2 RD in 1 3 TD out 3 TD out FF 2 RD in 1 NC TTT 4 IR ou 6 DSR in 1 DCD in 4 DTR out 6 DSR in 7 DTR tie
131. instrument has completed all pending operations The operation of this bit is not related to the OPC command which is a separate interface feature Refer to Paragraph 5 1 4 4 6 for more information Standard Event 7 6 5 4 3 2 1 0 Bit Status Register Not ome exe Not ave Not opc N ESR Used Used Used ame Fe C To Bit 5 ESB of Standard Event 7 6 5 4 3 2 1 0 Bit hi e a e Status Enable Register Not Nor SEA g moto en i ono s oe s n rane Figure 5 2 Standard Event Status Register 5 1 4 2 2 Operation Event Register Set The Operation Event Register reports the following instrument events PSH stable ramp done compliance Any or all of these events may be reported in the operation event summary bit through the enable register see Figure 5 4 The Operation Event Enable command OPSTE programs the enable register and the query command OPSTE reads it OPSTR reads and clears the Operation Event Register OPST reads the Operation Condition register The used bits of the Operation Event Register are described as follows PSH Stable Bit 2 This bit is set when the persistent switch is stable Ramp Done Bit 1 This bit is set when the output current ramp is completed Compliance Bit 0 This bit is set if the output is in compliance limit 5 8 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual Operation Condition Regi
132. ion without monitoring the SRQ It is also used when it is important to prevent any additional communication on the bus during a pending operation 5 14 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual 5 1 5 IEEE Interface Example Programs Two BASIC programs are included to illustrate the IEEE 488 communication functions of the instrument The first program was written in Visual Basic Refer to Paragraph 5 1 5 1 for instructions on how to setup the program The Visual Basic code is provided in Table 5 2 The second program is written in Quick Basic Refer to Paragraph 5 1 5 3 for instructions on how to setup the program The Quick Basic code is provided in Table 5 3 Finally a description of operation common to both programs is provided in Paragraph 5 1 5 5 While the hardware and software required to produce and implement these programs not included with the instrument the concepts illustrated apply to almost any application where these tools are available 5 1 5 1 IEEE 488 Interface Board Installation for Visual Basic Program This procedure works for Plug and Play GPIB Hardware and Software for Windows 98 95 This example uses the AT GPIB TNT GPIB card Install the GPIB Plug and Play Software and Hardware using National Instruments instructions 2 Verify that the following files have been installed to the Windows System folder a gpib 32 dll b gpib dll c gpib32ft dll Files b and c support any 1
133. istent mode When the supply is using this ramp rate the rate cannot be changed from the front panel using the Ramp Rate key since this is setup under the PSH Setup key If the persistent mode ramp rate is disabled then the ramp rate will remain the same if the magnet is in persistent mode or not but it can be changed at any time from the front panel using the Ramp Rate key To enable the persistent mode ramp rate continue from the persistent switch delay screen or press PSH Setup then Enter until the following persistent switch setup screen appears as a prompt for the persistent mode ramp rate Use the A or Y key to select the persistent mode ramp rate either Enabled or Disabled Press Enter to accept the new selection and continue to other persistent switch heater features Press Escape to cancel the new selection and return to the normal display 4 12 Operation Lake Shore Model 625 Superconducting MPS User s Manual If the persistent mode ramp rate is enabled then the ramp rate to be used while the magnet is in persistent mode needs to be entered Even though this ramp rate is typically much faster than the magnet ramp rate it should not be set too high as a fast change in current through the persistent switch can cause the switch to become normal and cause a quench Note that the persistent mode ramp rate will not be limited to the maximum ramp rate Refer to Paragraph 4 11 3 for information on the maximum ramp rate limit
134. k instruments fit horizontally in one rack width relief valve A type of pressure relief device which is designed to relieve excessive pressure and to reclose and reseal to prevent further flow of gas from the cylinder after reseating pressure has been achieved remanence The remaining magnetic induction in a magnetic material when the material is first saturated and then the applied field is reduced to zero The remanence would be the upper limit to values for the remanent induction Note that no strict convention exists for the use of remanent induction and remanence and in some contexts the two terms may be used interchangeably remanent induction The remaining magnetic induction in a magnetic material after an applied field is reduced to zero Also see remanence repeatability The closeness of agreement among repeated measurements of the same variable under the same conditions resistance temperature detector RTD Resistive sensors whose electrical resistance is a known function of the temperature made of e g carbon glass germanium platinum or rhodium iron resolution The degree to which nearly equal values of a quantity can be discriminated display resolution The resolution of the physical display of an instrument This is not always the same as the measurement resolution of the instrument Decimal display resolution specified as n digits has 10 possible display values A resolution of n and one half digits has 2x 10 possible values
135. k the value of the controlled quantity and using it to manipulate an input quantity so as to bring the value of the controlled quantity closer to a desired value Also known as closed loop control system A 2 Glossary of Terminology Lake Shore Model 625 Superconducting MPS User s Manual four lead measurement technique where one pair of excitation leads and an independent pair of measurement leads are used to measure a sensor This method reduces the effect of lead resistance on the measurement gamma A cgs unit of low level flux density where 100 000 gamma equals one oersted or 1 gamma equals 107 oersted gauss G The cgs unit for magnetic flux density B 1 gauss 10 tesla Named for Karl Fredrich Gauss 1777 1855 a German mathematician astronomer and physicist gaussian system units A system in which centimeter gram second units are used for electric and magnetic qualities general purpose interface bus GPIB Another term for the IEEE 488 bus germanium Ge A common temperature sensing material fabricated from doped germanium to make the Lake Shore GR family of resistance temperature sensor elements gilbert Gb A cgs electromagnetic unit of the magnetomotive force required to produce one maxwell of magnetic flux in a magnetic circuit of unit reluctance One gilbert is equal to 10 42 ampere turn Named for William Gilbert 1540 1603 an English physicist hypothesized that the Earth is a magnet gilbert per ce
136. l always ramp from one current setting to another There is no way to turn off the current ramping function but if a very fast ramp rate is desired a ramp rate as large as 99 999 A s can be entered to simulate a step change On most superconducting magnets the maximum rate at which it can be charged is usually stated Exceeding the maximum charging rate can cause the magnet to quench When the current ramp rate is entered or changed by crossing into a different ramp segment it will be limited in magnitude by the maximum ramp rate Refer to Paragraph 4 12 to setup the ramp segments and to Paragraph 4 11 to setup the maximum settings To change the current ramp rate press the Ramp Rate key The ramp rate value on the normal display will be highlighted to prompt for the new ramp rate value Use the data entry keys to enter the ramp rate value between 0 0001 and 99 999 A s Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence If the persistent mode ramp rate is enabled and the magnet is in persistent mode then the current ramp rate will not be allowed to change using the Ramp Rate key To change the current ramp rate either disable the persistent mode ramp rate feature or enter a new persistent mode ramp rate using the PSH Setup key Refer to Paragraph 4 14 4 to setup the persistent mode ramp rate The error box shown below will pop
137. l entries operations Example LOCK 1 123 term Enables keypad lock and sets the code to 123 5 38 Computer Interface Operation LOCK Input Returned Format MODE Input Format Example MODE Input Returned Format OPST Input Returned Format Remarks OPSTE Input Format Remarks OPSTE Input Returned Format OPSTR Input Returned Format Remarks Lake Shore Model 625 Superconducting MPS User s Manual Keyboard Lock Query LOCK term state code term n nnn Refer to command for description IEEE Interface Mode Command MODE lt mode gt term n mode 0 Local 1 Remote 2 Remote with local lockout MODE 2 term Places the Model 625 into remote mode with local lockout IEEE Interface Mode Query MODE term lt mode gt term n Refer to command for description Operational Status Query OPST term lt bit weighting gt term nnn The integer returned represents the sum of the bit weighting of the operational status bits Refer to Paragraph 5 1 4 2 2 for a list of operational status bits Operational Status Enable Command OPSTE bit weighting term nnn Each bit has a bit weighting and represents the enable disable mask of the corresponding operational status bit in the Operational Status Register This determines which status bits can set the corresponding summary bit in the Status Byte Register To
138. l rights reserved No portion of this manual may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mechanical photocopying recording or otherwise without the express written permission of Lake Shore Lake Shore Model 625 Superconducting MPS User s Manual CE DECLARATION OF CONFORMITY We Lake Shore Cryotronics Inc 575 McCorkle Blvd Westerville OH 43082 USA hereby declare that the equipment specified conforms to the following Directives and Standards Application of Council Directives 2006 95 EC LVD 2004 108 EC EMC Standards to which Conformity is declared EN 61010 1 2010 Overvoltage II Pollution Degree 2 EN 61326 1 2013 Class A Annex B Medel NORD cca rei 625 SPE 9 15 14 Director of Quality and Compliance Position Lake Shore Model 625 Superconducting MPS User s Manual Lake Shore Model 625 Superconducting MPS User s Manual Electromagnetic Compatibility EMC for the Model 625 Superconducting MPS Electromagnetic Compatibility EMC of electronic equipment is a growing concern worldwide Emissions of and immunity to electromagnetic interference is now part of the design and manufacture of most electronics To qualify for the CE Mark the Model 625 meets or exceeds the requirements of the European EMC Directive 89 336 EEC as a CLASS A product A Class A product is allowed to radiate more RF than a Class B product and must include
139. lay time of 10 to 20 seconds is usually sufficient During this delay time the Model 625 locks out any changes to the output magnet current to insure proper operation The persistent switch heater delay time can be changed at any time but the new value will not be used until the persistent switch heater is turned on or off again To enter a value for the persistent switch heater delay time continue from the persistent switch heater current screen or press PSH Setup then Enter until the following persistent switch setup screen appears as a prompt for the persistent switch heater delay time Use the data entry keys to enter the persistent switch heater delay time between 5 and 100 seconds Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence 4 14 4 Persistent Mode Ramp Rate A magnet is said to be in persistent mode when the persistent switch heater is off and the magnet is shorted by the persistent switch in its superconducting state While the magnet is in persistent mode the output current can be ramped at a faster rate since it is not ramping against the inductance of the magnet The Model 625 includes the persistent mode ramp rate feature that will automatically switch to the faster ramp rate when the magnet is in persistent mode If the feature is enabled the persistent mode ramp rate will be used when the magnet is in pers
140. leads Use lead wires heavy enough to limit the voltage drop to less than 0 5 volts per lead and keep conductor temperature under 85 C for a 35 C ambient temperature Table 2 1 lists the current capacity and total lead lengths for load connections Table 2 1 Current Capacity and Total Lead Lengths awg Area Capacity Resistivity Total Lead Length feet mm A Q 1000 feet 60A 120 A 0 53 5 245 0 09827 170 85 2 33 6 180 0 1563 107 53 4 21 2 135 0 2485 67 34 6 13 3 100 0 3951 42 8 8 4 75 0 6282 27 The Remote Voltage Sense connection can be used to monitor the voltage directly across the terminals of the magnet This will give a more accurate voltage reading across the terminals of the magnet by eliminating the voltage drop in the leads Some magnets manufacturers provide voltage sense connections directly at the terminals of the magnet If these are not available they can be added and the signals can be brought out of the dewar to be connected to the power supply If it is not desirable to add wiring inside the dewar the sense leads can be connected to the magnet current leads at the dewar The remote voltage sense input can only be used to read the voltage at the magnet terminals and cannot be used to control the voltage limit 25 HELIUM DEWARS Since superconducting magnets need to be run at cryogenic temperatures they are installed in dewars filled with liquid helium A dewar u
141. les Paragraph 7 12 1 illustrates suggested cables that can be used between the instrument and common computers The instrument uses drivers to generate the transmission voltage levels required by the RS 232C standard These voltages are considered safe under normal operating conditions because of their relatively low voltage and current limits The drivers are designed to work with cables up to 50 feet in length 5 24 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual 5 2 3 Hardware Support The Model 625 interface hardware supports the following features Asynchronous timing is used for the individual bit data within a character This timing requires start and stop bits as part of each character so the transmitter and receiver can resynchronized between each character Half duplex transmission allows the instrument to be either a transmitter or a receiver of data but not at the same time Communication speeds of 9600 19200 38400 or 57600 Baud are supported The Baud rate is the only interface parameter that can be changed by the user Hardware handshaking is not supported by the instrument Handshaking is often used to guarantee that data message strings do not collide and that no data is transmitted before the receiver is ready In this instrument appropriate software timing substitutes for hardware handshaking User programs must take full responsibility for flow control and timing as described in Paragra
142. lips screwdriver to tighten the 7 screws attaching the bottom panel to unit including the 4 screws that are used to attach the feet 6 Connect power cord to rear of unit and set power switch to On I 7 6 Service Lake Shore Model 625 Superconducting MPS User s Manual 7 10 FIRMWARE REPLACEMENT There are two integrated circuits IC that may potentially require replacement See Figure 7 3 for the IC location Main Firmware Erasable Programmable Read Only Memory EPROM U22 Contains the user interface software Has a sticker on top labeled M625F HEX and a date DAC Microcontroller U43 Contains software that controls the output DAC s Has a sticker on top labeled M625DACF HEX and a date Use the following procedure to replace either of these ICs 1 Follow the top of enclosure REMOVAL procedure in Paragraph 7 9 2 Locate the IC on the main circuit board See Figure 7 3 Note orientation of existing IC CAUTION The ICs are Electrostatic Discharge Sensitive ESDS devices Wear shock proof wrist straps resistor limited to 5 mA to prevent injury to service personnel and to avoid inducing an Electrostatic Discharge ESD into the device 3 Use IC puller to remove existing IC from the socket 4 Noting orientation of new IC use an IC insertion tool to place new device into socket Pu A ZEN 4 Pens vo Match notch on ipee Typical IC Eprom eps 5 Follow the top of enclosure INSTALLATION procedure in
143. ll only limit the value when a new setting is entered For example if a maximum ramp rate limit is entered that is less than the present ramp rate the present ramp rate will not be limited until a new ramp rate is entered 4 11 4 Maximum Output Current The maximum output current limits in magnitude the maximum output current that can be entered This setting will only limit the internal output current setting If the output current is being programmed by an external voltage then some provision must be made to insure that the programming voltage will never exceed the desired output current See Paragraph 4 18 to setup the External Programming mode Operation 4 7 Lake Shore Model 625 Superconducting MPS User s Manual To set the maximum output current limit press Max Settings The first maximum setting screen appears as a prompt for the maximum output current limit Use the data entry keys to enter the maximum output current limit value between 0 0000 and 60 0000 A Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence NOTE The maximum output current limit value can be set as high as 60 1000 A This can be used to compensate for current loss due to high resistance leads and for variances in calibration The output current is guaranteed to reach a minimum of 60 A but may not be able to reach 60 1 A in all circumstances
144. ltage Sense 2 NC 10 NC 3 Current Program 11 Current Program 4 NC 12 NC 5 Voltage Monitor 13 Voltage Monitor 6 NC 14 NC 7 Current Monitor 15 Current Monitor 8 NC Figure 7 4 ANALOG I O Connector Details PSH OU TPUT Heater Output bmp Pin Description Center Signal Shell Ground Figure 7 5 PSH OUTPUT Connector Details Service 7 9 Lake Shore Model 625 Superconducting MPS User s Manual T DIGITAL I O Digital IO bmp Pin Name Pin Name 1 Fault Out Common 14 Fault Out 2 NC 15 NC 3 Remote Inhibit Common 16 Remote Inhibit 4 NC 17 NC 5 Trigger Out Common not used 18 Trigger Out not used 6 19 NC 7 Trigger In Common 20 Trigger In 8 NC 21 NC 9 NC 22 NC 10 NC 23 NC 11 NC 24 NC 12 NC 25 NC 13 NC Figure 7 6 DIGITAL I O Connector Details 9 6 5 1 RS232 DTE RS 232 Connector bmp Model 625 Superconducting MPS Typical Computers DE 9P DTE DB 25P DTE DE 9P DTE Pin Description Pin Description Pin Description 1 No Connection 2 TD out 1 DCD in 2 Receive Data RD in 3 RD in 2 RD in 3 Transmit Data TD out 4 RTS out 3 TD out 4 Data Terminal Ready DTR out 5 CTS in 4 DTR out 5 Ground GND 6 DSR in 5 GND 6 Data Set Ready DSR in 7 GND 6 DSR in 7 Data Terminal Ready DTR out tied to 4 8 DCD in 7 RTS out 8 No Connection 20 DTR out 8 CTS in 9 No Connection 22 R
145. may be viewed but cannot be changed from the front panel The Model 625 has two keypad lock modes The lock all mode locks out changes to all parameters The lock limits mode locks out changes to all of the parameters except Output Setting Ramp Rate Voltage Limit Zero Output Stop Output Pause Output PSH On and PSH Off This allows the power supply to be operated without allowing any changes to the power supply setup A 3 digit code must be used to lock and unlock the keypad The factory default code is 123 and it can only be changed using a computer interface If the instrument parameters are set to default values the code is reset to the factory default The instrument parameters cannot be reset to default values from the front panel when the keypad is locked The following message box appears on the display if the user attempts to change a parameter while the keypad is locked NOTE The computer interface has a remote operation mode that may be mistaken for a locked keypad If the front panel Remote LED is lit press the Local key to change to local control of the instrument To lock or unlock the instrument keypad press and hold the Enter key for 5 seconds The following setup screen appears as a prompt for the keypad lock mode Use the A or V key to select the keypad lock mode Unlock Lock All or Lock Limits Press Enter to choose the new selection and continue to the keypad lock code verification The change
146. may set bit 6 RQS MSS of the Status Byte to generate a Service Request This command programs the enable register using a decimal value that corresponds to the binary weighted sum of all bits in the register Refer to Paragraph 5 1 4 4 Service Request Enable Register Query SRE term bit weighting gt term nnn Refer to command for description Status Byte Query STB term bit weighting gt term nnn This command is similar to a Serial Poll except it is processed like any other instrument command It returns the same result as a Serial Poll except that the Status Byte bit 6 RQS MSS is not cleared Refer to paragraph 5 1 4 4 4 Trigger Event TRG term Starts the trigger event See TRIG command for trigger setup Computer Interface Operation 5 35 TST Input Returned Format Remarks WAI Input Remarks BAUD Input Format BAUD Input Returned Format DFLT Input Remarks DISP Input Format DISP Input Lake Shore Model 625 Superconducting MPS User s Manual Self Test Query TST term status term n status 0 No errors found 1 Errors found The Model 625 reports status based on test done at power up Wait to Continue Command WAI term This command is not supported in the Model 625 RS 232 Baud Rate Command BAUD lt bps gt term n lt bps gt Specifies Baud rate 0 9600 Baud 1 19200 Baud 2 38400 Baud 3 57600 Baud RS
147. mpliance voltage limit It is recommended that the compliance voltage limit be set to an appropriate value for the magnet before turning on the PSH Operation 4 13 Lake Shore Model 625 Superconducting MPS User s Manual 4 16 QUENCH DETECTION A magnet quenches when a part of the superconducting wire in the magnet becomes resistive When a section of the magnet becomes resistive it will begin to heat and cause more of the magnet to become resistive This causes an unstoppable chain reaction that will result in the magnet dissipating all of its energy into heat There are typically three ways in which a magnet can quench One way is if the cryogen is allowed to boil off to the point in which the magnet is no longer covered Another way is to ramp the current in the magnet at a rate that is greater than specified The final way is to exceed the maximum current specified for the magnet Although a magnet quench is undesirable it typically is non destructive Most magnets are designed to be able to handle dissipating the heat generated with the magnet at rated current Exceeding the maximum current could cause damage to the magnet if it were to quench in this state since there is more energy in the system than it was designed for If a magnet quench occurs the level of the cryogen should be checked before operating the magnet system again since much of it may have boiled off Quench detection is important to alert the user and to protect the magne
148. must not exceed 255 characters in length A command string is issued by the computer and instructs the instrument to either perform a function or change a parameter setting When a command is issued the computer is acting as talker and the instrument as listener The format is Xcommand mnemonic gt lt space gt lt parameter data gt lt terminators gt Computer Interface Operation 5 3 Lake Shore Model 625 Superconducting MPS User s Manual Command mnemonics and parameter data necessary for each one is described in Paragraph 5 3 Terminators must be sent with every message string A query string is issued by the computer and instructs the instrument which response to send Queries are issued similar to commands with the computer acting as talker and the instrument as listener The query format is lt query mnemonic gt lt gt lt space gt lt parameter data gt lt terminators gt Query mnemonics are often the same as commands with the addition of a question mark Parameter data is often unnecessary when sending queries Query mnemonics and parameter data if necessary is described in Paragraph 5 3 Terminators must be sent with every message string Issuing a query does not initiate a response from the instrument A response string is sent by the instrument only when it is addressed as a talker and the computer becomes the listener The instrument will respond only to the last query it receives The
149. n 3 6 3 Trigger In The Trigger In connection on the Digital I O connector is an input that is used to start an output current ramp The trigger can only be armed from the computer interface using the TRIG command to setup a new output current setpoint When the Trigger In line is activated the power supply will begin ramping to the new setpoint Once the instrument has been triggered the TRIG command needs to be sent again along with a new setpoint to rearm the trigger The Trigger In input is TTL compatible and a logic low will activate it The signal is internally pulled up to allow operation with a simple switch closure Refer to Figure 3 5 3 7 PERSISTENT SWITCH HEATER OUTPUT The persistent switch heater output is a controlled DC current source capable of sourcing up to 125 mA with a jumper selectable compliance voltage limit of 15 V or 24 V The default setting is 24V Refer to Paragraph 7 11 to configure the compliance voltage limit of the persistent switch heater output The actual voltage compliance limit is dependant on load but guaranteed to be at least 12 V or 21 V depending on the setting The heater output current is software settable in 1 mA steps from 10 to 125 mA Typically the magnet manufacturer specifies the persistent switch heater current The minimum load that the persistent switch heater can drive is 10 Q If the persistent switch heater is less than 10 a series resistance needs to be added or else the PSH circuit will fals
150. n n nnnn Refer to command for description 5 42 Computer Interface Operation SETF Input Format Remarks SETF Input Returned Format SETI Input Format Remarks SETI Input Returned Format SETV Input Format Remarks SETV Input Returned Format STOP Input Remarks Lake Shore Model 625 Superconducting MPS User s Manual Output Field Setting Command SETF lt field gt term nnn nnnEtnn lt field gt Specifies the output field setting 0 0000 601 000E 03 G or 0 0000 60 1000E 00 T Sets the field value that the output will ramp to at the present ramp rate The setting entered will be based on the field constant and the field units Refer to the FLDS command Output Field Setting Query SETF term lt field gt term nnn nnnEtnn Refer to command for description Output Current Setting Command SETI lt current gt term nn nnnn current Specifies the output current setting 0 0000 60 1000A Sets the current value that the output will ramp to at the present ramp rate Setting value is limited by LIMIT Output Current Setting Query SETI term current term nn nnnn Refer to command for description Output Compliance Voltage Setting Command SETV lt voltage gt term n nnnn lt voltage gt Specifies the output compliance voltage setting 0 1000 5 0000 V Sets the output compliance voltage This value will be
151. n Table 5 9 a In the Code Editor window under the Object dropdown list select General Add the statement Public gSend as Boolean b Double Click on cmdSend Add code segment under Private Sub cmdSend Click as shown in Table 5 9 c Inthe Code Editor window under the Object dropdown list select Form Make sure the Procedure dropdown list is set at Load The Code window should have written the segment of code Private Sub Form Load Add the code to this subroutine as shown in Table 5 9 d Double Click on the Timer control Add code segment under Private Sub Timerl Timer as shown in Table 5 9 e Make adjustments to code if different Com port settings are being used 13 Save the program 14 Run the program The program should resemble the following is Serial Interface Program Type exit to end program Command Response m PIS x 15 Type in a command or query in the Command box as described in Paragraph 5 2 7 3 16 Press Enter or select the Send button with the mouse to send command 17 Type Exit and press Enter to quit 5 28 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual Table 5 9 Visual Basic Serial Interface Program Public gSend As Boolean Global used for Send button state Private Sub cmdSend Click gSend True End Sub Routine to handle Send button press Set Flag to True Private Sub Form Load
152. nal RS 232C standard specifies 25 pins but both 9 and 25 pin connectors are commonly used in the computer industry Many third party cables exist for connecting the instrument to computers with either 9 or 25 pin connectors Paragraph 7 12 1 gives the most common pin assignments for 9 and 25 pin connectors Please note that not all pins or functions are supported by the Model 625 The instrument serial connector is the plug half of a mating pair and must be matched with a socket on the cable If a cable has the correct wiring configuration but also has a plug end a gender changer can be used to mate two plug ends together The letters DTE near the interface connector stand for Data Terminal Equipment and indicate the pin connection of the directional pins such as transmit data TD and receive data RD Equipment with Data Communications Equipment DCE wiring can be connected to the instrument with a straight through cable As an example Pin 3 of the DTE connector holds the transmit line and Pin 3 of the DCE connector holds the receive line so the functions complement It is likely both pieces of equipment are wired in the DTE configuration In this case Pin 3 on one DTE connector used for transmit must be wired to Pin 2 on the other used for receive Cables that swap the complementing lines are called null modem cables and must be used between two DTE wired devices Null modem adapters are also available for use with straight through cab
153. nd button press Set Flag to True Private Sub Form Load Dim strReturn As String Dim term As String Dim strCommand As String Dim intDevice As Integer frmIEEE Show term Chr 13 amp Chr 10 strReturn Call ibdev 0 12 0 T10s 1 amp H140A intDevice Call ibconfig intDevice ibcREADDR 1 Main code section Used to return response Terminators Data string sent to instrument Device number used with IEEE Show main window Terminators are lt CR gt lt LF gt Clear return string Initialize the IEEE device Setup Repeat Addressing Do Do Wait loop DoEvents Give up processor to other events Loop Until gSend True Loop until Send button pressed gSend False Set Flag as False strCommand frmIEEE txtCommand Text Get Command strReturn Clear response display strCommand UCase strCommand Set all characters to upper case If strCommand EXIT Then Get out on EXIT End End If Call ibwrt intDevice strCommand amp term Send command to instrument If ibsta And EERR Then Check for IEEE errors do error handling if needed Handle errors here End If If InStr strCommand lt gt 0 Then Check to see if query strReturn Space 100 Build empty return buffer Call ibrd intDevice strReturn Read back response If ibsta And EERR Then Check for IEEE errors do error handling if needed Handle errors here End If If strReturn lt gt Then Check if empty string strReturn RTrim str
154. nd query strings through user programs the instrument issues responses Two or more command or query strings can be chained together in one communication but they must be separated by a semi colon The total communication string must not exceed 255 characters in length A command string is issued by the computer and instructs the instrument to perform a function or change a parameter setting The format is lt command mnemonic gt lt space gt lt parameter data gt lt terminators gt Command mnemonics and parameter data necessary for each one is described in Paragraph 5 3 Terminators must be sent with every message string Computer Interface Operation 5 25 Lake Shore Model 625 Superconducting MPS User s Manual Message Strings Continued A query string is issued by the computer and instructs the instrument to send a response The query format is Xquery mnemonic gt lt gt lt space gt lt parameter data gt lt terminators gt Query mnemonics are often the same as commands with the addition of a question mark Parameter data is often unnecessary when sending queries Query mnemonics and parameter data if necessary is described in Paragraph 5 3 Terminators must be sent with every message string The computer should expect a response very soon after a query is sent A response string is the instruments response or answer to a query string The instrument will respond to the last query or queries it receives The response can b
155. necessary to keep the output of the power supply stable into the purely inductive load of a superconducting magnet This is common practice in many superconducting magnet power supplies This typically results in negligible error when driving a superconducting load The displayed output current is compensated for the current loss through the resistor and reflects the actual current in the magnet This impedance can cause unexpected results in systems that have larger than normal lead resistance or other resistive impedance If there is a voltage across the output terminals of the supply then a small amount of current will flow through the stabilizing resistor given by the equation I 2 V 25 where I is the current through the resistor and V is the voltage across the output terminals This will reduce the amount of current flowing through the magnet The output current reading is compensated for the current flowing through the resistor and is representative of the current in the magnet If it is necessary to have the current in the magnet exactly equal a certain value the output current setting can be increased until the output current reading is equal to the desired amount In some circumstances it may be desirable to disable the reading compensation In this case the output current reading will closely match the output current setting but the reading may not be indicative of the current in the magnet since the current in the resistor is not accounted for
156. ned in the firmware must not be modified Any changes made to the code is at the user s risk Lake Shore will assume no responsibility for damage or errors incurred as result of any changes made to the firmware Under the terms of this agreement you may only use the Model 625 firmware as physically installed in the instrument Archival copies are strictly forbidden You may not decompile disassemble or reverse engineer the firmware If you suspect there are problems with the firmware return the instrument to Lake Shore for repair under the terms of the Limited Warranty specified above Any unauthorized duplication or use of the Model 625 firmware in whole or in part in print or in any other storage and retrieval system is forbidden TRADEMARK ACKNOWLEDGMENT Many manufacturers and sellers claim designations used to distinguish their products as trademarks Where those designations appear in this manual and Lake Shore was aware of a trademark claim they appear with initial capital letters and the TM or symbol CalCurve Carbon Glass Cernox M Duo Twist High Temperature Cernox Quad Lead Quad Twist Rox SoftCal and Thermox are trademarks of Lake Shore Cryotronics Inc MS DOS and Windows 95 98 NT 2000 are trademarks of Microsoft Corp NI 488 2 is a trademark of National Instruments PC XT AT and PS 2 are trademarks of IBM Copyright O 2003 2004 2010 and 2014 2015 by Lake Shore Cryotronics Inc Al
157. net is in a sealed dewar To ensure that the diodes are not damaged by the power supply the compliance voltage limit of the supply should be set to a voltage below the protection diode range It is also recommended that some form of quench detection be used to force the output of the power supply to 0 amps when a quench is detected ensuring that no additional current is being supplied to the diodes The Model 625 offers both internal quench detection and a remote inhibit line that can be connected to an external quench detection circuit 2 3 PERSISTENT SWITCHES Some superconducting magnets are constructed with a persistent switch A persistent switch is a length of superconducting wire that shorts across the terminals of the magnet This length of wire can be heated and drives it into a resistive state so that a voltage can be applied across the magnet terminals and the magnet can be charged or discharged When the heater is shut off this section of wire will cool and become superconducting again and the magnet will be in persistent mode At this time the power supply can be ramped to zero current and even removed from the system while the magnet holds its charge One of the reasons to use a persistent switch is when a very stable field is required When the magnet is in persistent mode all of the current is being circulated within the magnet with no interference from outside sources Another reason to use a persistent switch is when it is desired t
158. ng the ramp segments table All five of the ramp segments are shown on the display at the same time The segments should be entered in order of increasing current An entry of 0 A will indicate the end of the table and the instrument will not search beyond that segment When the segment number is highlighted use the A or W key to scroll through the ramp segments Press the Enter key when the desired segment number is highlighted and continue to the current field When the current field is highlighted use the numerical keypad to enter the upper current setting for that ramp segment in amps Press Enter to accept the new selection and continue to the ramp rate field Press Escape to restart the setting sequence and enter a new value Press Escape again to highlight the segment number When the ramp rate field is highlighted use numerical keypad to enter the applicable ramp rate in A s Press Enter to accept the new selection and continue to the next segment Press Escape to restart the setting sequence and enter a new value Press Escape again to highlight the segment number Similarly enter or edit all ramp segments When complete press the Escape key while the segment number field is highlighted to exit the ramp segment edit screen and return to the normal display Operation 4 9 Lake Shore Model 625 Superconducting MPS User s Manual 4 13 FIELD CONSTANT In a superconducting magnet magnetic field is directly proportional
159. nj o JIN j lt x z lt je jo gt jajo y N y grin lt ix E lt ciAjuojmjo jo u a 1 Q o Oo o o o Oo o 1 1 1 1 1 1 1 1 2i 2 25 l2 0 o o o 2 O Oo lolol E 2 2 o o 2 o Oo o o 2 o lo l z 2 o 2 o 2 o 2 Ol O 2 O O o l Y o 3 3 x 7 lo ajo ojala o Oo z zir x x c OIyIz O m m oc o qm R jy a Ajo a c milo m American Wire Gage AWG Wiring sizes are defined as diameters in inches and millimeters as follows AWG Dia In Dia mm AWG Dia In Dia mm AWG Dia In Dia mm AWG Dia In Dia mm 1 0 2893 7 348 11 0 0907 2 304 21 0 0285 0 7230 31 0 0089 0 2268 2 0 2576 6 544 12 0 0808 2 053 22 0 0253 0 6438 32 0 0080 0 2019 3 0 2294 5 827 13 0 0720 1 829 23 0 0226 0 5733 33 0 00708 0 178 4 0 2043 5 189 14 0 0641 1 628 24 0 0207 0 5106 34 0 00630 0 152 5 0 1819 4 621 15 0 0571 1 450 25 0 0179 0 4547 35 0 00561 0 138 6 0 1620 4 115 16 0 0508 1 291 26 0 0159 0 4049 36 0 00500 0 127 7 0 1443 3 665 17 0 0453 1 150 27 0 0142 0 3606 37 0 00445 0 1131 8 0 1285 3 264 18 0 0403 1 024 28 0 0126 0 3211 38 0 00397 0 1007 9 0 1144 2 906 19 0 0359 0 9116 29 0 0113 0 2859 39 0 00353 0 08969 10 0 1019 2 588 20 0 0338 0 8118 30 0 0100 0 2546 40 0 00314 0 07987 ambient temperature The temperature of the surrounding medium such as gas or liquid which comes into contact with the 1 apparatus ampere The constant current th
160. nless otherwise specified lock in amplifier An amplifier that uses some form of automatic synchronization with an external reference signal to detect and measure very weak electromagnetic radiation at radio or optical wavelengths in the presence of very high noise levels M Symbol for magnetization See magnetization magnetic air gap The air space or non magnetic portion of a magnetic circuit magnetic field strength H The magnetizing force generated by currents and magnetic poles For most applications the magnetic field strength can be thought of as the applied field generated for example by a superconducting magnet The magnetic field strength is not a property of materials Measure in SI units of A m or cgs units of oersted magnetic flux density B Also referred to as magnetic induction This is the net magnetic response of a medium to an applied field H The relationship is given by the following equation B uo H M for SI and B H 47M for cgs where H magnetic field strength M magnetization and uo permeability of free space 4x x 107 H m magnetic hysteresis The property of a magnetic material where the magnetic induction B for a given magnetic field strength H depends upon the past history of the samples magnetization magnetic induction B See magnetic flux density magnetic moment m This is the fundamental magnetic property measured with dc magnetic measurements systems such as a vibrating sample ma
161. nment Printing Office Washington D C 20402 Temperature Scales B 1 Lake Shore Model 625 Superconducting MPS User s Manual Table B 2 Recommended SI Values for Physical Constants a 0 0073 F truct tant 2 2h ine Structure Constant u0ce2 137 0360 Elementary Charge fe 1 6022 x 10 C h Plank s C 6 6262 x 10 J Hz STI h h 2n 1 0546 x 10 s Avogadro s Constant 6 0220 x 10 mol 30 Electron Rest Mass 9 7102 X107 kE 5 4858 x 104 u 1 6726 x 10 kg Proton Rest Mass mp is 27 1 0087 u EUM SOIA 1 esc OR RT Data abbreviated to 4 decimal places from CODATA Bulletin No 11 ICSU CODATA Central Office 19 Westendstrasse 6 Frankfurt Main Germany Copies of this bulletin are available from this office Molar Volume Ideal Gas To 273 15K po 1 atm Vm RTo po 0 0224 n mol B 2 Temperature Scales Lake Shore Model 625 Superconducting MPS User s Manual APPENDIX C HANDLING LIQUID HELIUM AND NITROGEN C1 0 GENERAL Use of liquid helium LHe and liquid nitrogen LN is often associated with the Model 625 Superconducting MPS Although not explosive there are a number of safety considerations to keep in mind in the handling of LHe and LN C2 0 PROPERTIES LHe and LN are colorless odorless and tasteless gases Gaseous nitrogen makes up about 78 percent of the Earth s atmosphere while helium comprises only about 5 ppm Most helium is recovered from natural gas deposits Once colle
162. ntimeter Practical cgs unit of magnet intensity Gilberts per cm are the same as oersteds Greek alphabet The Greek alphabet is defined as follows Alpha a A Iota 1 I Rho p P Beta p B Kappa K K Sigma o x Gamma Y T Lambda A A Tau t T Delta A Mu u M Upsilon v Y Epsilon E Nu v N Phi o Zeta G Z Xi E Chi X X Eta n H Omicron o O Psi y Y Theta 0 Pi T II Omega 0 Q ground A conducting connection whether intentional or accidental by which an electric circuit or equipment is connected to the Earth or to some conducting body of relatively large extent that serves in place of the Earth Note It is used for establishing and maintaining the potential of the Earth or of the conducting body or approximately that potential on conductors connected to it and for conducting ground current to and from the Earth or of the conducting body H Symbol for magnetic field strength See Magnetic Field Strength Hall effect The generation of an electric potential perpendicular to both an electric current flowing along a thin conducting material and an external magnetic field applied at right angles to the current Named for Edwin H Hall 1855 1938 an American physicist hertz Hz A unit of frequency equal to one cycle per second hysteresis The dependence of the state of a system on its previous history generally in the form of a lagging of a physical effect behind its cause Also see magnetic hysteresis IEC International Electrotec
163. nting a Model 625 Power Supply oooonoccccococoncccnoncconccononcnnonccnnncanonc cnn cn nn rc rn cana n nn rra rennen nnns 3 9 4 1 Model 625 Output Current Display i 4 1 4 2 Model 625 Magnet Field Display cnn nono cnn nnonnrn ran nn nera n cnn nn r ore rnnnn rre nennen enn rennen 4 2 5 1 Model 625 Statlis SYStc Mss rnein aida eee reed dean 5 5 5 2 Standard Event Status Register 5 nire es ia aint pi tear 5 8 5 3 Operation Event Register et 5 9 5 4 Hardware Error Status Register 2 en cie Re RR liana ISORADIO 5 10 5 5 Operational Error Status Register nennen nennen nennen nnne senten rennen rens 5 11 5 6 PSH Error Status Register o er e inn e cs 5 11 5 7 Status Byte Register and Service Request Enable Register i 5 13 5 8 GPIBO Setting Configuration io ia oio eren tl need ed pec aa cede bete aee 5 16 5 9 DEV 12 Device Template Configuration ii 5 16 5 10 Typical National Instruments GPIB Configuration from IBCONF EXE i 5 21 7 1 Fuse Drawetticisicigicthest cna iota a ea dete I at eie tides 7 2 7 2 Power FUS ACCOSS os ie id a iaia lai ERN e ia RERO e viens le 7 8 7 3 Location Of Important Internal Components 7 8 7 4 ANALOG I O Connector Details sie cic ne anie ali dedo 7 9 7 5 PSH OUTPUT Gonnector Details pite e RR SITE RCA RORIS ERREUR 7 9 7 6 DIGITAL l O Gonnector Details PRU Pe Re RR ERR EF iii 7 10 7
164. o hold a particular magnet field for an extended period of time such as in a MRI system Once the magnet is in persistent mode the power supply can be removed from the system and used elsewhere It is also possible on some systems to remove the vapor cooled leads from the dewar to further reduce the amount of helium boil off The magnet manufacturer will specify the current necessary to turn on the persistent switch heater Do not use any more current than is necessary since that will result in excess helium boil off It is important when turning on the persistent switch heater that the current setting of the power supply is equal to the current in the magnet If the current does not match the current in the magnet will ramp to the current setting of the power supply at the compliance voltage limit This may cause the power supply to incorrectly detect a quench Magnet System Design 2 3 Lake Shore Model 625 Superconducting MPS User s Manual 2 4 MAGNET CURRENT LEADS The power supply should be placed close to the magnet to reduce the length of the lead wires The resistance of the wires becomes very important when such large currents are being supplied to the magnet The rate at which a magnet can be charged depends on the voltage that can be supplied across the terminals of the magnet given by the equation V L di dt The voltage is limited by the maximum voltage the power supply can output minus the voltage that is lost through the magnet
165. oject Menu click Components to bring up a list of additional controls available in VB6 Scroll through the controls and select Microsoft Comm Control 6 0 Select OK In the toolbar at the left of the screen the Comm Control will have appeared as a telephone icon 1 2 3 4 5 6 7 a b c d Select the Comm control and add it to the form Add controls to form Add three Label controls to the form Add two TextBox controls to the form Add one CommandButton control to the form Add one Timer control to the form 8 Onthe View Menu select Properties Window 9 Inthe Properties window use the dropdown list to select between the different controls of the current project Label1 Command Label3 Label 10 Set the properties of the controls as defined in Table 5 8 11 Save the program Computer Interface Operation 5 27 Lake Shore Model 625 Superconducting MPS User s Manual Table 5 8 Serial Interface Program Control Properties Current Name Property New Value Labell Name IbIExitProgram Caption Type exit to end program Label2 Name lblCommand Caption Command Label3 Name IbIResponse Caption Response Textl Name txtCommand Text lt blank gt Text2 Name txtResponse Text lt blank gt Command1 Name cmdSend Caption Send Default True Forml Name frmSerial Caption Serial Interface Program Timerl Enabled False Interval 10 12 Add code provided i
166. om CGS tO SI Units ce ee EUER ante ER era lie RIO B 1 B 2 Recommended SI Values for Physical Constants i B 2 C 1 Comparison of Liquid Helium and Liquid Nitrogen i C 1 iv Table of Contents Lake Shore Model 625 Superconducting MPS User s Manual CHAPTER 1 INTRODUCTION 1 0 GENERAL This chapter provides an introduction to the Model 625 Superconducting Magnet Power Supply The Model 625 was designed and manufactured in the United States of America by Lake Shore Cryotronics Inc The Model 625 features include the following True 4 quadrant bipolar 60 A 5 V output 0 1 mA output setting resolution Linear regulation minimizes noise and ripple to 0 006 of maximum current into a 1 mQ load 1 0 mA stability per hour Two units can be connected in parallel for 120 A operation CE compliance to both the low voltage directive and the electromagnetic compatibility EMC directive pending 1 1 DESCRIPTION The Model 625 Superconducting Magnet Power Supply is the ideal supply for small to medium sized superconducting magnets used in high sensitivity materials research applications The Model 625 is a practical alternative to both the larger one size fits all superconducting magnet supplies and the endless adaptations of generic power supplies By limiting output power Lake Shore was able to concentrate on the performance requirements of the most demanding magnet users The resulting Model 625 prov
167. on the rear panel for the line voltage setting The letter T on the fuse rating indicates that the instrument requires a time delay or slow blow fuse Fuse values should be verified any time line voltage configuration is changed Instructions for changing and verifying a line fuse are given in Paragraph 7 5 3 3 3 Power Cord The Model 625 includes a 3 conductor power cord that mates with the IEC 320 C14 line cord receptacle Line voltage is present on the two outside conductors and the center conductor is a safety ground The safety ground attaches to the instrument chassis and protects the user in case of a component failure A CE approved power cord is included with instruments shipped to Europe a domestic power cord is included with all other instruments unless otherwise specified when ordered Always plug the power cord into a properly grounded receptacle to ensure safe operation of the instrument The delicate nature of measurement being taken near this instrument may necessitate additional grounding including ground strapping of the instrument chassis In these cases the operators safety should remain the highest priority and low impedance from the instrument chassis to safety ground should always be maintained Installation 3 3 Lake Shore Model 625 Superconducting MPS User s Manual 3 3 4 Power Switch The power switch is on the front panel of the Model 625 and turns line power to the instrument On and Off When the circle is depres
168. onal notes on using either IEEE 488 Interface program Ifyou enter a correctly spelled query without a nothing will be returned Incorrectly spelled commands and queries are ignored Commands and queries should have a space separating the command and associated parameters Leading zeros and zeros following a decimal point are not needed in a command string but are sent in response to a query A leading is not required but a leading is required 5 1 6 Troubleshooting New Installation Check instrument address Always send terminators Send entire message string at one time including terminators Send only one simple command at a time until communication is established Be sure to spell commands correctly and use proper syntax ye die Un cb ES Attempt both Talk and Listen functions If one works but not the other the hardware connection is working so look at syntax terminators and command format 7 Ifonly one message is received after resetting the interface check the repeat addressing setting It should be enabled Old Installation No Longer Working 8 Power instrument off then on again to see if it is a soft failure 9 Power computer off then on again to see if the IEEE card is locked up 10 Verify that the address has not been changed on the instrument during a memory reset 11 Check all cable connections Intermittent Lockups 12 Check cable connections and length
169. onse display Set all characters to upper case Get out on EXIT Send command to instrument Check to see if query Wait for response Add 1 to timeout if no character Wait for 10 millisecond timer Loop Until frmSerial Timerl Enabled False ZeroCount ZeroCount 1 Else ZeroCount 0 strHold frmSerial MSComml Input strReturn strReturn strHold End If Wend If strReturn lt gt Then strReturn Mid strReturn 1 InStr strReturn Else strReturn No Response End If frmSerial txtResponse Text strReturn strHold ZeroCount 0 If Timeout at 2 seconds Reset timeout for each character Read in one character Add next character to string Get characters until terminators Check if string empty Term 1 Strip terminators Send No Response Put response in textbox on main form Reset holding string Reset timeout counter Private Sub Timerl Timer frmSerial Timerl Enabled False End Sub Routine to handle Timer interrupt Turn off timer Computer Interface Operation 5 29 Lake Shore Model 625 Superconducting MPS User s Manual 5 2 7 2 Quick Basic Serial Interface Program Setup The serial interface program listed in Table 5 10 works with QuickBasic 4 0 4 5 or Qbasic on an IBM PC or compatible running DOS or in a DOS window with a serial interface It uses the COMI communication port at 9600 Baud Use the following procedure to develop the Serial Interface
170. ont panel or interface and record I reading 4 Calculate the zero offset constant Treading Vshun Rshunt 5 Send CALZ 0 zero offset constant 6 Verify the Model 625 output current reading to match the actual output current within 20 0005 mA 7 Send CALSAVE to write this calibration to non volatile memory 7 14 Service Lake Shore Model 625 Superconducting MPS User s Manual 7 13 3 3 Calibrate Output Voltage Reading Zero This step assumes that the previous two steps are successful and the current through the shunt resistor is quite low resulting in virtually no voltage across the Model 625 output terminals Send CALZ 5 0 to set the current reading offset constant to 0 Get the Model 625 output voltage reading by front panel or interface Calculate zero offset constant output voltage reading Send CALZ 5 zero offset constant Verify the Model 625 output voltage reading to be 0 0 0001 V Send CALSAVE to write this calibration to non volatile memory 13 3 4 Calibrate Remote Voltage Sense Reading Zero Short the remote voltage sense lines pins 1 and 9 of the analog I O connector Send CALZ 6 0 To set the remote voltage reading offset constant to 0 Calculate zero offset constant remote voltage sense reading Send CALZ 6 zero offset constant Verify the Model 625 remote voltage reading to be 0 30 0001 V Send CALSAVE to write this calibration to non volatile
171. or conditions are indicated on the main display along with an audible beeper Extended error descriptions are available under the Status key The keypad is arranged logically to separate the different functions of the instrument The most common functions of the power supply are accessed using a single button press The keypad can be locked to either lock out all changes or to lock out just the instrument setup parameters allowing the output of the power supply to be changed amp akeShore Model 625 Superconducting Magnet Power Supply 625 Front bmp Figure 1 1 Model 625 Front Panel Introduction 1 3 1 2 SPECIFICATIONS Output Type Current Generation Current Range Compliance Voltage Maximum Power Load Reactance Current Ripple Max Current Ripple Frequency Temperature Coefficient Line Regulation Source Impedance Stability 1 h Stability 24 h Isolation Parallel Operation Protection Output Programming Internal Current Setting Resolution Settling Time Accuracy Operation Protection Internal Current Ramp Ramp Rate Update Rate Ramp Segments Operation Protection External Current Programming Sensitivity Resolution Accuracy Bandwidth 3 dB Input Resistance Operation Connector Limits Compliance Voltage Setting Range Resolution Accuracy Lake Shore Model 625 Superconducting MPS User s Manual Bipolar Four Quadrant DC Current Source L
172. ow humidity may generate up to 35 000 volts of static electricity Current technology trends toward greater complexity increased packaging density and thinner dielectrics between active elements which results in electronic devices with even more ESD sensitivity Some electronic parts are more ESDS than others ESD levels of only a few hundred volts may damage electronic components such as semiconductors thick and thin film resistors and piezoelectric crystals during testing handling repair or assembly Discharge voltages below 4000 volts cannot be seen felt or heard 7 8 1 Identification of Electrostatic Discharge Sensitive Components The following are various industry symbols used to label components as ESDS oy CAUTION Service 7 5 Lake Shore Model 625 Superconducting MPS User s Manual 7 8 2 Handling Electrostatic Discharge Sensitive Components Observe all precautions necessary to prevent damage to ESDS components before attempting installation Bring the device and everything that contacts it to ground potential by providing a conductive surface and discharge paths As a minimum observe these precautions De energize or disconnect all power and signal sources and loads used with unit Place unit on a grounded conductive work surface 1 2 3 Ground technician through a conductive wrist strap or other device using 1 MQ series resistor to protect operator 4 Ground any tools such as soldering equipment that will
173. owering with warm water The patient should not drink alcohol or smoke Keep warm and rest Call a physician immediately C 2 Handling LHe and LN
174. ph 5 2 6 5 2 4 Character Format A character is the smallest piece of information that can be transmitted by the interface Each character is 10 bits long and contains data bits bits for character timing and an error detection bit The instrument uses 7 bits for data in the ASCII format One start bit and one stop bit are necessary to synchronize consecutive characters Parity is a method of error detection One parity bit configured for odd parity is included in each character ASCII letter and number characters are used most often as character data Punctuation characters are used as delimiters to separate different commands or pieces of data Two special ASCII characters carriage return CR 0DH and line feed LF OAH are used to indicate the end of a message string Table 5 7 Serial Interface Specifications Connector Type 9 pin D style connector plug Connector Wiring DTE Voltage Levels EIA RS 232C Specified Transmission Distance 50 feet maximum Timing Format Asynchronous Transmission Mode Half Duplex Baud Rate 9600 19200 38400 57600 Handshake Software timing Character Bits 1 Start 7 Data 1 Parity 1 Stop Parity Odd Terminators CR ODH LF OAH Command Rate 20 commands per second maximum 5 2 5 Message Strings A message string is a group of characters assembled to perform an interface function There are three types of message strings commands queries and responses The computer issues command a
175. plicable to the sale of the product to you CERTIFICATION Lake Shore certifies that this product has been inspected and tested in accordance with its published specifications and that this product met its published specifications at the time of shipment The accuracy and calibration of this product at the time of shipment are traceable to the United States National Institute of Standards and Technology NIST formerly known as the National Bureau of Standards NBS FIRMWARE LIMITATIONS Lake Shore has worked to ensure that the Model 625 firmware is as free of errors as possible and that the results you obtain from the instrument are accurate and reliable However as with any computer based software the possibility of errors exists In any important research as when using any laboratory equipment results should be carefully examined and rechecked before final conclusions are drawn Neither Lake Shore nor anyone else involved in the creation or production of this firmware can pay for loss of time inconvenience loss of use of the product or property damage caused by this product or its failure to work or any other incidental or consequential damages Use of our product implies that you understand the Lake Shore license agreement and statement of limited warranty FIRMWARE LICENSE AGREEMENT The firmware in this instrument is protected by United States copyright law and international treaty provisions To maintain the warranty the code contai
176. put crowbar SCR has been thrown to prevent damage to the magnet or the supply Low Line Voltage Detected The input line voltage is detected to be too low The instrument may not be able to attain the compliance voltage setting The output crowbar SCR has been thrown to maintain control of the magnet Internal Temperature Fault The internal temperature of the supply has exceeded 80 C The output crowbar SCR has been thrown to prevent damage to the supply Table 7 2 Operational Errors Magnet Discharging The magnet is currently discharging through the output crowbar SCR This error Through Crowbar can be cleared when the magnet is completely discharged Magnet Quench Detected A magnet quench has been detected because the output current changed at a rate greater than the current step limit This error can be cleared when the magnet is completely discharged Remote Inhibit Detected An external remote inhibit condition was triggered The output current is set to zero This error can be cleared when the remote inhibit trigger is released Internal Temperature High The internal temperature of the supply has exceeded 75 C If the output current is increasing the output current ramp will stop If the output current is decreasing the compliance voltage will be limited to 1 V This error can be cleared when the internal temperature drops below 70 C High Line Voltage Detected The input line voltage is dete
177. r command to instrument to generate a command error Monitor bus Monitor the bus until the Service Request interrupt SRQ is sent Serial Poll the bus to determine which instrument sent the interrupt and clear the RQS bit in the Status Byte Read and clear the Standard Event Status Register allowing an SRQ to be generated on another command error Initiate Serial Poll ESR Computer Interface Operation 5 13 Lake Shore Model 625 Superconducting MPS User s Manual 5 1 4 4 4 Using Status Byte Query STB The Status Byte Query STB command is similar to a Serial Poll except it is processed like any other instrument command The STB command returns the same result as a Serial Poll except that the Status Byte bit 6 RQS MSS is not cleared In this case bit 6 is considered the MSS bit Using the STB command does not clear any bits in the Status Byte Register 5 1 4 4 5 Using the Message Available MAV bit Status Byte summary bit 4 MAV indicates that data is available to read into your bus controller This message may be used to synchronize information exchange with the bus controller The bus controller can for example send a query command to the Model 625 and then wait for MAV to set If the MAV bit has been enabled to initiate an SRQ the user s program can direct the bus controller to look for the SRQ leaving the bus available for other use The MAV bit will be clear whenever the output buffer is empty
178. ragraph 4 5 to set the output current There are certain circumstances in which the current will not be allowed to change just like when entering a new output current setpoint An error box will pop up explaining why the current is not allowed to change These error boxes are described in Paragraph 4 5 4 9 STOP OUTPUT CURRENT The Stop Output key will stop the output current ramp within two seconds after the key is pressed even if the magnet is ramping against the compliance voltage A new output current setpoint must be entered for the output current to begin ramping again 4 10 PAUSE OUTPUT CURRENT The Pause Output key will pause the output current ramp within two seconds after the key is pressed While the output current ramp is paused the Ramping LED will blink Pressing the Pause Output key while the output current ramp is paused will cause the output current ramp to resume ramping to the original output current setpoint 4 11 MAXIMUM SETTING LIMITS The Model 625 offers maximum setting limits for output current compliance voltage limit and output current ramp rate Typically the properties of the superconducting magnet will dictate what these maximum settings should be Exceeding the maximum settings stated by the magnet manufacturer can cause the magnet to quench or be damaged These maximum settings should be entered before the magnet system is used to prevent a quench if a setting is incorrectly entered Note that the maximum settings wi
179. rameter value Press and hold to reset parameters to default values Refer to Paragraph 4 21 Setup the field constant value and units Refer to Paragraph 4 13 Setup the external current programming mode Refer to Paragraph 4 18 Setup RS 232 and IEEE computer interfaces Refer to Paragraph 4 20 Setup ramp segment values Refer to Paragraph 4 12 Setup maximum setting values for output current voltage and ramp rate Refer to Paragraph 4 11 Displays a summary of the instrument status Refer to Paragraph 4 17 Accepts a new parameter value Press and hold to lock keypad Refer to Paragraph 4 19 Numeric data entry within a setting sequence Increments a parameter selection or value Decrements a parameter selection or value Turns the persistent switch heater on Refer to Paragraph 4 15 Turns the persistent switch heater off Places the instrument to Remote mode Refer to Paragraph 5 1 2 Returns the instrument to Local mode if in Remote Refer to Paragraph 5 1 2 4 3 2 General Keypad Operation The Model 625 uses three basic keypad operations direct operation setting selection and data entry for the majority of operator interface A few specialized keypad operations such as ramp segment entry are described in the individual operation paragraphs Direct Operation Key functions occur immediately when the key is pressed Zero Output Stop Output and Pause Output are examples of keys that operate this way Setting Selection
180. re without a Return Authorization number Refer to Paragraph 7 2 Current contact information can always be found on the Lake Shore web site www lakeshore com Lake Shore Cryotronics Inc a _ Instrument Service Department Mailing Address 575 McCorkle Blvd Westerville OH USA 43082 8888 E mail Address sales lakeshore com Sales i service lakeshore com Instrument Service Telephone 614 891 2244 Sales p i 614 891 2243 ext 131 Instrument Service Fax 614 818 1600 Sales i 614 818 1609 Instrument Service When contacting Lake Shore please provide your name and complete contact information including e mail address if possible It is often helpful to include the instrument model number and serial number located on the rear panel of the instrument as well as the firmware revision information as described in Paragraph 4 21 7 2 RETURNING PRODUCTS TO LAKE SHORE If it is necessary to return the Model 625 for recalibration repair or replacement a Return Authorization RA number must be obtained from a factory representative or from the Lake Shore web site Do not return a product to Lake Shore without an RA number The following information must be provided to Lake Shore in order to obtain an RA number Instrument model and serial number 2 User name company address phone number and e mail address 3 Malfunction symptoms 4 Description of the system in which the product is used If possible the orig
181. record V readingneg Set the Model 625 output current to I 0 18 4 5 R load For example if R load 1 Q set the Model 625 output current to 4 68 A Wait 30 seconds Measure the Model 625 actual output voltage at the output terminals and record V measuredpos This voltage must be between 4 0 and 5 0 volts 4 5 V nominal Get the Model 625 output voltage reading by front panel or interface and record Veadingpos Calculate gain constant per Equation 4 Equation 4 Verify the gain factor to be 1 0 02 Send CALG 5 gain constant Verify the Model 625 output voltage reading to match the actual output voltage within 20 0005 V Set the Model 625 output current to 0 A Send CALSAVE to write this calibration to non volatile memory 7 13 3 9 Calibrate Remote Voltage Sense Reading Gain 1 2 3 mA Qi Ur Tm 10 11 12 Connect the PSH output in parallel with the DVM a 100 resistor as a load and the remote voltage sense lines Send CALG 6 1 To set the remote voltage sense reading gain constant to 1 Set the PSH switch heater to 50 mA and turn on the PSH output to provide a 5 0 V DC level to be measured by the remote voltage sense lines Measure the PSH output voltage and record V measured Verify V measured 5 0 0 1 V Get the Model 625 output voltage reading by front panel or interface and record V reading Calculate the gain constant per Equation 5 Equation 5 Verify the
182. rent rating 2 2 4 Maximum Magnet Current Although superconducting wire can carry more current than non superconducting wire of the same size the amount of current that it can carry is not unlimited If the critical current of the wire is exceeded the wire will no longer be superconducting and will revert to its normal state causing the magnet to quench Commercially purchased magnets have been designed to work up to a maximum stated current The magnet should be able to handle a quench up to the rated current of the magnet Do not exceed the maximum current rating of the magnet or the magnet can quench and possibly be damaged 2 2 5 Magnet Quench Protection Diodes Many superconducting magnets have protection diodes installed across the terminals of the magnet These diodes will turn on in the event of a quench and will help dissipate some of the magnets energy Typically the diodes are attached to the magnet itself and are submerged in the cryogen At 4 2 K the forward voltage of the diodes may be on the order of 10 volts If the magnet quenches the energy dissipated in the diodes will warm them resulting in a decrease in their forward voltage If this voltage drops below the compliance voltage limit of the power supply the power supply will continue to source current to the diodes eventually damaging them and causing them to short This would require that the protection diodes be replaced which could be a significant expense especially if the mag
183. rent to drive the Analog Current Programming Input for its gain calibration During the procedure this resistor will dissipate only 0 25 W DC Voltmeter DVM The voltmeter must measure VDC accurately to 10 s of uV if resolution to 10 s of mA from the Model 625 is to be assured The HP34401 or better is suggested 7 13 3 Calibration Procedure The following calibration steps should be performed exactly in the order provided 7 13 3 1 Calibrate Current Output Zero The 1 mQ shunt resistor is wired directly across the Model 625 output terminals with 4 AWG wire Cable length is relatively unimportant but should be less than 5 feet to the shunt resistor Voltage across the shunt resistor is to be monitored by the DVM 1 Send CALZ 10 0 to set the output offset constant to 0 2 Set the Model 625 output current to 0 A 3 Measure the actual voltage across the shunt and record Vshunt 4 Calculate the zero offset constant Vsnun Rshunt 5 Send CALZ 10 zero offset constant 6 Resetthe Model 625 output current to O A loads the new offset setting 7 Verify the actual output current to be less than 1 mA 8 Send CALSAVE to write this calibration to non volatile memory 7 13 3 2 Calibrate Current Reading Zero 1 Send CALZ 0 0 to set the current reading offset constant to 0 2 Measure the actual voltage across the shunt and record V sunt 3 Get the Model 625 output current reading by fr
184. response can be a reading value status report or the present value of a parameter Response data formats are listed along with the associated queries in Paragraph 5 3 5 1 4 Status System 5 1 4 1 Overview The Model 625 implements a status system compliant to the IEEE 488 2 1992 standard The status system provides a method of recording and reporting instrument information and is typically used to control the Service Request SRQ interrupt line A diagram of the status system is shown in Figure 5 1 The status system is made up of register sets the Status Byte register and the Service Request Enable register Each register set consists of three types of registers condition event and enable 5 1 4 1 1 Condition Registers Each register set except the Standard Event Register set includes a condition register as shown in Figure 5 1 The condition register constantly monitors the instrument status The data bits are real time and are not latched or buffered The register is read only 5 1 4 1 2 Event Registers Each register set includes an event register as shown in Figure 5 1 Bits in the event register correspond to various system events and latch when the event occurs When an event bit is set subsequent events corresponding to that bit are ignored Set bits remain latched until the register is cleared by a query command such as ESR or a CLS command The register is read only 5 1 4 1 3 Enable Registers Each register set in
185. rial Poll When a Status Byte summary bit or MAV bit is enabled by the Service Request Enable Register and goes from 0 to 1 bit 6 RQS MSS of the status byte will be set This will send a service request SRQ interrupt message to the bus controller The user program may then direct the bus controller to serial Poll the instruments on the bus to identify which one requested service the one with bit 6 set in its status byte Serial polling will automatically clear RQS of the Status Byte Register This allows subsequent serial polls to monitor bit 6 for an SRQ occurrence generated by other event types After a serial poll the same event or any event that uses the same Status Byte summary bit will not cause another SRQ unless the event register that caused the first SRQ has been cleared typically by a query of the event register The serial poll does not clear MSS The MSS bit stays set until all enabled Status Byte summary bits are cleared typically by a query of the associated event register refer to Paragraph 5 1 4 4 4 The programming example in Table 5 3 initiates an SRQ when a command error is detected by the instrument Table 5 3 Programming Example to Generate an SRQ Command or Operation Description ESR Read and clear the Standard Event Status Register ESE 32 Enable the Command Error CME bit in the Standard Event Status Register SRE 32 Enable the Event Summary Bit ESB to set the RQS ABC Send imprope
186. rminals and record V measured Measure the actual voltage across the shunt and record Vshunt Calculate and record Imax Vshunt Rshunt Send CALG 10 100 To set the output current gain trim constant to maximum Wait 10 seconds Measure the actual voltage across the shunt and record V shunt O ECON oU E O A Calculate and record Imaxpostrim V shunt Rshunt EAE Rh o Send CALG 10 100 To set the output current gain trim constant to minimum Wait 10 seconds Measure the actual voltage across the shunt and record V shunt Rh o a Pu N Calculate and record Iminpostrim V shunt Rshunt Set the Model 625 to 55A V ramp rate 20 A s nominal Wait 30 seconds for settling a NU Oa tA Measure the actual voltage across the shunt and record V shunt ne oo Calculate and record Imin V snun Rstunt o Send CALG 10 100 To set the output current gain trim constant to maximum Wait 10 Seconds Measure the actual voltage across the shunt and record V shunt N NN Ne O Calculate and record Imaxnegtrim V shunt Rshunt N W Send CALG 10 100 To set the output current gain trim constant to minimum Wait 10 seconds Measure the actual voltage across the shunt and record V shunt N NN AU A Calculate and record Iminnegtrim Vshunt Rshunt N Send CALG 10 0 To return the output current gain trim const
187. rsistent switch heater current is specified by the magnet manufacturer Exceeding the recommended current will cause excess helium boil off and can possibly damage the heater To enter a value for the persistent switch heater current continue from the persistent switch heater enable screen or press PSH Setup then Enter until the following persistent switch setup screen appears as a prompt for the persistent switch heater current Use the data entry keys to enter the persistent switch heater current value between 5 and 125 mA Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence Operation 4 11 Lake Shore Model 625 Superconducting MPS User s Manual The persistent switch heater current can only be changed when the heater is off If the current is changed while the heater is on or warming the following error box will appear and the new setting will be ignored 4 14 3 Persistent Switch Heater Delay When a persistent switch heater is turned on or off it is in an indeterminate state for a period of time while the switch is warming or cooling The persistent switch heater delay should be set to a value that insures that the persistent switch has fully transitioned from one state to the other This value is typically not given by the magnet manufacturer but can be estimated by observation For most systems a de
188. s CAUTION For continued protection against fire hazard replace only with the same fuse type and rating specified for the line for the line voltage selected NOTE Test fuse with an ohmmeter Do not rely on visual inspection of fuse Locate line input assembly on the instrument rear panel See Figure 7 2 Turn front panel power switch Off O Remove instrument power cord With a small screwdriver release the drawer holding the line voltage selector and fuses Remove and discard both existing fuses Replace with proper Slow Blow time delay fuse ratings as follows 100 120 V 10 0 A T 250 V 0 25x1 25 220 240 V 5 0 A T 250 V 5x20 mm Oe oras Re assemble line input assembly in reverse order Verify voltage indicator in the line input assembly window Connect instrument power cord Turn front panel power switch On I SEED SES 7 6 ERROR MESSAGES The following messages appear on the lower part of the instrument display when it identifies a problem during operation The Fault LED will light in conjunction with the error message A more extensive description of the error message can shown by pressing the Status key If the error condition can be cleared it can be done by pressing the Status key while in the error status display Refer to Paragraph 4 17 for a description of the error status display Service 7 3 Lake Shore Model 625 Superconducting MPS User s Manual The error messages are divided into two
189. s Byte Query aai i QNCH Quench Parameter Query see 41 TRG Trigger Eventi eee yp ae etes RATE Current Ramp Rate Setting Cmd 41 TST Self Test QUE RORIS RATE Current Ramp Rate Setting Query 41 WAI Wait To Continue Cmd i RATEP Persistent Mode Ramp Rate Parameter Cmd Al BAUD RS 232 Baud Rate Cmd ses RATEP Persistent Mode Ramp Rate Query 41 BAUD RS 232 Baud Rate Query RDGF Field Output Reading Query sss 41 DFLT Factory Defaults Cmd see RDGI Current Output Reading Query sss 42 DISP Display Parameter Cmd ses RDGRV Remote Voltage Sense Reading Query 42 DISP Display Parameter Query RDGV Output Voltage Reading Query sss 42 ERCL Error Clear Cmd see RSEG Ramp Segments Enable Cmd 42 ERST Error Status Query sss RSEG Ramp Segments Enable Query s 42 ERSTE Error Status Enable Cmd sss 37 RSEGS Ramp Segments Parameters Cmd 42 ERSTE Error Status Enable Query sss 37 RSEGS Ramp Segments Parameters Query 42 ERSTR Error Status Register Query sss 37 SETF Output Field Setting Cmd sss 43
190. s are the centimeter gram and second Chebychev polynomials A family of orthogonal polynomials which solve Chebychev s differential equation Chebychev differential equation A special case of Gauss hypergeometric second order differential equation 1 x2 f x xf x n f x 0 closed loop See feedback control system coercive force coercive field The magnetic field strength H required to reduce the magnetic induction B in a magnetic material to zero coercivity generally used to designate the magnetic field strength H required to reduce the magnetic induction B in a magnetic material to zero from saturation The coercivity would be the upper limit to the coercive force cryotronics The branch of electronics that deals with the design construction and use of cryogenic devices Curie temperature Tc Temperature at which a magnetized sample is completely demagnetized due to thermal agitation Named for Pierre Curie 1859 1906 a French chemist current source A type of power supply that supplies a constant current through a variable load resistance by automatically varying its compliance voltage A single specification given as compliance voltage means the output current is within specification when the compliance voltage is between zero and the specified voltage curve A set of data that defines the temperature response of a temperature sensor It is used to convert the signal from the sensor to
191. s can be purchased from Lake Shore or other electronic suppliers Cable lengths are limited to 2 meters for each device and 20 meters for the entire bus The Model 625 can drive bus with up to 10 loads If more instruments or cable length is required a bus expander must be used Computer Interface Operation 5 1 Lake Shore Model 625 Superconducting MPS User s Manual 5 1 1 Changing IEEE 488 Interface Parameters Two interface parameters address and terminators must be set from the front panel before communication with the instrument can be established Other interface parameters can be set via the interface using the device specific commands provided in Paragraph 5 3 To set the IEEE 488 parameters press the Computer Interface key and press Enter to skip past Serial Interface Baud Rate The following computer interface screen appears as a prompt for the IEEE 488 address Use the A or V key to select an address between 1 and 30 The default is twelve Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display The next computer interface screen appears as a prompt for the IEEE 488 terminators Use the A or W key to select one of the following terminators CR LF LF CR LF and EOI The default is Cr Lf Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new sel
192. se calibrations are done through the computer interface and the calibration constants are stored in the non volatile memory in the instrument There are no trim pots inside the Model 625 and the cover does not have to be removed to calibrate the instrument The remaining features of the Model 625 do not require calibration to operate within their specified tolerances 7 13 1 Calibration Interface Computer interface commands are included in the Model 625 specifically for calibration These commands work with either the IEEE 488 or RS 232C interface Refer to Section 7 13 4 for a complete description of each calibration command It is always recommended to read out old calibration coefficients using the CALZ and CALG interface queries before attempting to calibrate This will give the operator experience with the interface command data formatting and typical values If the old values are saved they can be reloaded in the case of accidental loss of data during calibration New calculated calibration coefficients should be very similar to the old values Discrepancy between the old and new values of more than 0 1 of gain calibration coefficients or 0 1 of range for zero coefficients could indicate an error in the calibration procedure or a hardware failure Do not attempt to recalibrate a damaged instrument The instrument will use the new calibration coefficients as soon as they are sent with the either the CALZ or CALG interface command but they ar
193. se safety precautions during all phases of instrument operation service and repair Failure to comply with these precautions or with specific warnings elsewhere in this manual violates safety standards of design manufacture and intended instrument use Lake Shore assumes no liability for Customer failure to comply with these requirements The Model 625 protects the operator and surrounding area from electric shock or burn mechanical hazards excessive temperature and spread of fire from the instrument Environmental conditions outside of the conditions below may pose a hazard to the operator and surrounding area Indoor use Maximum relative humidity 80 for temperature up to Altitude to 2000 meters 31 C decreasing linearly to 50 at 40 C Temperature for safe operation 5 C to 40 C Power supply voltage fluctuations not to exceed 10 Overvoltage category II of the nominal voltage Pollution degree 2 Ground The Instrument To minimize shock hazard the instrument is equipped with a 3 conductor AC power cable Plug the power cable into an approved three contact electrical outlet or use a three contact adapter with the grounding wire green firmly connected to an electrical ground safety ground at the power outlet The power jack and mating plug of the power cable meet Underwriters Laboratories UL and International Electrotechnical Commission IEC safety standards Ventilation The instrument has ventilation holes
194. sed power is Off When the line is depressed power is On 3 4 MAGNET CABLE CONNECTIONS Magnet cable connections are made at the OUTPUT and OUTPUT terminals on the rear panel These plated copper bus bars accommodate 4 inch M6 mounting hardware Use load wires heavy enough to limit the voltage drop to less than 0 5 volts per lead This ensures proper regulation and prevents overheating while carrying the output current The remote voltage sense leads can be used to measure the actual magnet voltage Keep conductor temperature under 85 C 185 F for a 35 C 95 F ambient Table 3 1 lists the current capacity and total lead lengths for load connections Lake Shore sells magnet cables in 10 and 20 foot lengths Refer to Paragraph 6 2 for ordering accessories Table 3 1 Current Capacity and Total Lead Lengths AWG Area Capacity Resistivity Total Lead Length feet mm A Q 1000 feet 60A 120A 0 53 5 245 0 09827 170 85 2 33 6 180 0 1563 107 53 4 21 2 135 0 2485 67 34 6 13 3 100 0 3951 42 8 8 4 75 0 6282 27 3 5 ANALOG INPUT OUTPUT CONNECTIONS The Analog I O connector provides connections to analog signals used to monitor or control the power supply Two inputs are provided one to program the current output and one used to monitor the remote voltage sense leads Two outputs are also provided to monitor the output current and the output voltage Refer to the instrument specifications
195. single phase 50 or 60 Hz 850 VA 483 mm W x 178 mm H x 520 mm D 19 in x 7 in x 20 5 in rack mount integrated rack mount ears 27 2 kg 60 lbs CE Mark Low voltage compliance to EN61010 3 EMC compliance to EN55022 1 1 year Description Superconducting Magnet Power Supply Two Model 625s one dual supply interconnect cable kit Instrument configured for 100 VAC with U S power cord Instrument configured for 120 VAC with U S power cord Instrument configured for 120 VAC with U S power cord and universal European power cord and fuses for 220 240 setting extra charge for this option Instrument configured for 220 VAC with European power cord Instrument configured for 240 VAC with European power cord Instrument configured for 220 VAC with a 220 V 6 15P U S power cord Model 625 user s manual Two front handles Two rear handles protectors Output shorting bar and terminal fasteners 25 pin D sub mating connector digital I O 15 pin D sub mating connector analog I O Calibration Certificate 1 m 3 3 ft long IEEE 488 GPIB computer interface cable assembly 10 ft 60 A magnet cable kit AWG 4 20 ft 60 A magnet cable kit AWG 4 Dual supply interconnect cable kit including magnet cables and safety interlock cable Instrument recalibration with certificate Instrument recalibration with certificate and data Introduction Lake Shore Model 625 Superconducting MPS User s Manual 1 3 SAFETY SUMMARY Observe the
196. ster OPST Operation Event Register OPSTR To Bit 7 OSB of Status Byte Register See Figure 5 1 Operation Event Enable Register OPSTE OPSTE 7 6 5 4 3 2 1 0 ai Not Not Not Not Not free eoe amo Figure 5 3 Operation Event Register 5 1 4 3 Error Status Register Sets As shown in Figure 5 1 there are three register sets in the error status system of the Model 625 Hardware Error Status Register Operational Error Status Register and the Persistent Switch Error Register 5 1 4 3 1 Hardware Error Status Register Set The Hardware Error Status Register reports the following instrument hardware error events DAC processor not responding output control failure output over voltage output over current low line voltage temperature fault Any or all of these events may be reported in the standard event summary bit through the enable register see Figure 5 2 The Hardware Error Status Register is the first value of the three values associated with the Error Status Registers The Error Status Enable command ERSTE programs the enable register and the query command ERSTE reads it ERSTR reads and clears the Error Status Register The used bits of the Error Status Event Register are described as follows DAC Processor Not Responding DAC Bit 5 This bit is set to indicate that communication to the DAC processor has failed Output Control Failure OCF Bit 4 This bit is set if there is a failure on
197. sually consists of one or more reservoirs surrounded by a vacuum jacket This vacuum jacket insulates the reservoir from room temperatures In dewars with multiple reservoirs the outside reservoir is normally filled with liquid nitrogen as a way to further reduce the heat transfer from the liquid helium filled inner reservoir Most dewars are made from stainless steel although they can also be made from glass or epoxy fiberglass and aluminum Stainless steel is used because it is very rugged has low thermal conductivity and can easily be welded to different types of metals The most basic dewars are of an all welded construction with an opening in the top for direct access to the cryogen reservoir The dewar will have an evacuation valve to evacuate the vacuum jacket surrounding the cryogen reservoir There will also be a pressure relief valve to protect the vacuum jacket in case a leak should develop This leak would allow cold cryogen into the vacuum jacket where it will expand upon contact with the room temperature wall This pressure relief valve is set to open between 2 and 5 psi to safely vent the leaking gas The superconducting magnet can either be supported by the insert or supported by a base in the bottom of the dewar If the magnet is in the base of the dewar it is usually installed when the dewar is built and can only be removed or serviced by cutting the dewar apart Any insert that is placed in the helium reservoir should contain a number of
198. t Send command to instrument Get data back each time Test for returned string String is present if CR is seen Strip off terminators Print return string No string present if timeout Get next command 5 22 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual 5 1 5 5 Program Operation Once either example program is running try the following commands and observe the response of the instrument Input from the user is shown in bold and terminators are added by the program The word term indicates the required terminators included with the response ENTER COMMAND IDN Identification query Instrument will return a string identifying itself RESPONSE LSCI MODEL625 1234567 06122003 term ENTER COMMAND RDGR 1 Ohm reading query Instrument will return a string with the present resistance reading from channel 1 RESPONSE 273 150E 00 term ENTER COMMAND HTRRNG 0 Heater range command Instrument will turn off the heater No response will be sent ENTER COMMAND HTRRNG Heater range query Instrument will return a string with the present heater range setting RESPONSE O term ENTER COMMAND HTRRNG 1 HTRRNG Heater range command followed by a query Instrument will change to heater Low setting then return a string RESPONSE 1 term with the present setting The following are additi
199. t of the current through the known resistance of the calibration resistor This resistor must be accurately measured and its actual value R Shunt used to determine the actual current flow For example if the resistor is measured at 0 99661 mQ the actual current flowing is calculated by Equation 1 Equation 1 This resistor must withstand the full current of the Model 625 and do so with a minimum of heating that can easily change the resistance and therefore the current measurement At 60 A this resistor only dissipates 3 6 W Even so it is highly recommended to mount the resistor on a heat sink with forced air cooling to minimize temperature rise Alpha PSBWROO10F is suggested Load Resistor This resistor is placed in series with the 1 mQ resistor to create a compliance voltage to calibrate the voltage reading of the Model 625 This resistor value should be in a range from 0 075 to 5 Q The actual value of this resistor is not critical since only a voltage measurement is made to calibrate a voltage reading on the Model 625 To determine the amount of power the resistor will be required to handle reference the formula in Section 7 13 3 8 step 4 This specifies the amount of current through the resistor Note the output voltage is compliance limited to 5 V For example a 0 075 resistor will develop 270 W and a 5 Q resistor will develop 5 W PSH Resistor This is simply a 1 W 100 Q resistor used to develop a voltage from the PSH output cur
200. t system When a quench is detected the output current setting of the supply is immediately set to 0 A If the power supply was still supplying current to the magnet system after a quench it is possible that the protection diodes in the magnet would turn on and then the diodes would take the full current load destroying themselves in the process During a quench the current in the magnet will quickly drop to zero The 625 constantly monitors the output current and calculates an actual current ramp rate If the current changes at a rate greater than the current step limit then a quench is detected The current step limit should be set to a value greater than any expected ramp rate 4 16 1 Quench Detection Enable Quench detection can be enabled or disabled If quench detection is disabled another form of quench detection should be used to avoid damage to the magnet system To configure quench detection press Quench Detect The first quench detection setup screen appears as a prompt for the quench detection mode Use the A or V key to select the quench detection mode either Enable or Disable Press Enter to accept the new selection and continue to the next screen Press Escape to cancel the new selection and return to the normal display 4 16 2 Current Step Limit In order for a quench to be detected the output current must change at a rate greater than or equal to the current step limit setting The current step limit should be se
201. t to a rate greater than what the magnet is capable of ramping at if it were operating correctly The formula V L di dt can be used to calculate the maximum ramp rate For example the Model 625 has a maximum compliance voltage of 5 V so for a 10 H magnet the maximum ramp rate that is possible is 5 10 or 0 5 A s The current step limit should be set slightly above the maximum theoretical ramp rate typically above 0 2 A s more Therefore a good setting for the current step limit for a 10 H magnet would be about 0 7 A s To enter a value for the current step limit continue from the quench detection mode screen or press Quench Detect then Enter until the following quench detection setup screen appears as a prompt for the current step limit value Quench detection must be enabled to set the current step limit 4 14 Operation Lake Shore Model 625 Superconducting MPS User s Manual Use the data entry keys to enter the current step limit value between 0 0100 and 10 000 A s Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence 4 17 ERROR STATUS DISPLAY Error messages appear on the lower part of the instrument display when it identifies a problem during operation The Fault LED will also light to indicate error conditions blinking for operational errors on solid for instrument hardware errors Refer to Paragraph 7 6 for a
202. term Command will set the output field setting to 2000 SETF 2000 term Command will set the output field setting to 2000 5 32 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual Table 5 11 Command Summary Command Function Page Command Function Page CLS Clear Interface Cmd eee 34 OPST Operational Status Query ses 39 ESE Event Status Enable Cmd sss 34 OPSTE Operational Status Enable Cmd 39 ESE Event Status Enable Query sss 34 OPSTE Operational Status Enable Query 39 ESR Event Status Register Query sss 34 OPSTR Operational Status Register Query 39 IDN Identification Query sse 34 PSH Persistent Switch Heater Cmd 40 OPC Operation Complete Cmd sss 35 PSH Persistent Switch Heater Query sss 40 OPC Operation Complete Query sess 35 PSHIS Last Current Setting for PSH Query 40 RST Reset Instrument Cmd sse PSHS Persistent Switch Parameter Cmd 40 SRE Service Request Enable Cmd PSHS Persistent Switch Parameter Query 40 SRE Service Request Enable Query QNCH Quench Parameter Cmd sss 40 STB Statu
203. ters 10 feet 60 A AWG 4 6262 Magnet Cable Kit 6 meters 20 feet 60 A AWG 4 6263 Dual supply interconnect cable kit including magnet cables and safety interlock cable CAL 625 CERT Instrument recalibration with certificate CAL 625 DATA Instrument recalibration with certificate and data Options and Accessories 6 1 Lake Shore Model 625 Superconducting MPS User s Manual Options and Accessories Lake Shore Model 625 Superconducting MPS User s Manual This Page Intentionally Left Blank Options and Accessories 6 3 Lake Shore Model 625 Superconducting MPS User s Manual CHAPTER 7 SERVICE This chapter provides basic service information for the Model 625 Superconducting Magnet Power Supply Customer service of the product is limited to the information presented in this chapter Factory trained service personnel should be consulted if the instrument requires repair 7 1 CONTACTING LAKE SHORE CRYOTRONICS If a Lake Shore product was purchased through a dealer or representative please use that resource for prompt sales or service information When contacting Lake Shore directly please specify the name of a department if do not know the name of an individual Questions regarding product applications price availability and shipments should be directed to sales Questions regarding instrument calibration or repair should be directed to instrument service Do not return a product to Lake Sho
204. that is or may have been in contact with the liquid or cold gas or with cold pipes or equipment Long sleeve shirts and cuffless trousers that are of sufficient length to prevent liquid from entering the shoes are recommended C5 0 RECOMMENDED FIRST AID Every site that stores and uses LHe and LN should have an appropriate Material Safety Data Sheet MSDS present The MSDS may be obtained from the manufacturer distributor The MSDS will specify the symptoms of overexposure and the first aid to be used A typical summary of these instructions is provided as follows If symptoms of asphyxia such as headache drowsiness dizziness excitation excess salivation vomiting or unconsciousness are observed remove the victim to fresh air If breathing is difficult give oxygen If breathing has stopped give artificial respiration Call a physician immediately If exposure to cryogenic liquids or cold gases occurs restore tissue to normal body temperature 98 6 F as rapidly as possible then protect the injured tissue from further damage and infection Call a physician immediately Rapid warming of the affected parts is best achieved by bathing it in warm water The water temperature should not exceed 105 F 40 C and under no circumstances should the frozen part be rubbed either before or after rewarming If the eyes are involved flush them thoroughly with warm water for at least 15 minutes In case of massive exposure remove clothing while sh
205. the following warning WARNING This is a Class A product In a domestic environment this product may cause radio interference in which case the user may be required to take adequate measures The instrument was tested under normal operating conditions with sensor and interface cables attached If the installation and operating instructions in the User s Manual are followed there should be no degradation in EMC performance This instrument is not intended for use in close proximity to RF Transmitters such as two way radios and cell phones Exposure to RF interference greater than that found in a typical laboratory environment may disturb the sensitive measurement circuitry of the instrument Pay special attention to instrument cabling Improperly installed cabling may defeat even the best EMC protection For the best performance from any precision instrument follow the grounding and shielding instructions in the User s Manual In addition the installer of the Model 625 should consider the following Shield measurement and computer interface cables Leave no unused or unterminated cables attached to the instrument Make cable runs as short and direct as possible Higher radiated emissions is possible with long cables Do not tightly bundle cables that carry different types of signals Lake Shore Model 625 Superconducting MPS User s Manual Lake Shore Model 625 Superconducting MPS User s Manual TABLE OF CONTENTS Chapter
206. the normal display 4 20 2 Changing IEEE 488 Interface Parameters Two interface parameters address and terminators must be set from the front panel before IEEE 488 communication with the instrument can be established Other interface parameters can be set via the interface using the device specific commands provided in Paragraph 5 3 To set the IEEE 488 parameters press the Computer Interface key and press Enter to skip past Serial Interface Baud Rate The following computer interface screen appears as a prompt for the IEEE 488 address Use the A or V key to select an address between 1 and 30 The default is twelve Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display The next computer interface screen appears as a prompt for the IEEE 488 terminators Operation 4 17 Lake Shore Model 625 Superconducting MPS User s Manual Use the A or W key to select one of the following terminators CR LF LF CR LF and EOI The default is Cr Lf Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display 4 24 DEFAULT PARAMETER VALUES It is sometimes desirable to reset instrument parameters to their default values This data is stored in nonvolatile memory called EEPROM Instrument calibration is not affected by this operation
207. the output control board Output Over Voltage OOV Bit 3 This bit is set if the output voltage exceeded the compliance voltage limit setting Output Over Current OOC Bit 2 This bit is set if the output current is above 62 A exceeding the maximum output current of the instrument Low Line Voltage LLV Bit 1 This bit is set if the power line voltage drops below an acceptable amplitude Temperature Fault TF Bit 0 This bit is set if the internal temperature of the instrument exceeded the maximum safe value of 80 C Computer Interface Operation 5 9 Lake Shore Model 625 Superconducting MPS User s Manual Error Status 7 6 5 4 3 2 14 0 Bit Condition Register Not Not eser os os oe or onm rv Hardware Errors To Bit 2 HESB of Status Byte Register Enable Register ere enden s oss we 0000 00 us v name Figure 5 4 Hardware Error Status Register 5 1 4 3 2 Operational Error Status Register Set The Operational Error Status Register reports the following instrument operational error events magnet discharging through crowbar magnet quench detected remote inhibit detected temperature high high line voltage external current program error calibration error Any or all of these events may be reported in the standard event summary bit through the enable register see Figure 5 2 The Operational Error Status Register is the second value of the three values associated
208. the primary address Enable Auto Serial Polling No forms the Talk Address TA Enable CIC Protocol Bus Timing 500nsec EXAMPLE Selecting a primary address Parallel Poll Duration of 10 yields the following Use this GPIB board Yes 10 32 42 Listen address y 10 64 74 Talk address National Instruments DEV12 Configuration GPIB PC2 2A Ver 2 1 Primary GPIB Address Select the primary GPIB address by Secondary GPIB Address y using the left and right arrow keys Serial Poll Timeout This address is used to compute the talk and listen addresses which identify the board or device on the Set EOI with EOS on Writes Yes GPIB Valid primary addresses range from 0 to 30 00H to 1EH Send EOI at end of Write Yes Adding 32 to the primary address forms the Listen Address LA Enable Repeat Addressing Yes Adding 64 to the primary address forms the Talk Address TA EXAMPLE Selecting a primary address of 10 yields the following 10 32 42 Listen address 10 64 74 Talk address Fl Help F6 Reset Value F9 Esc Return to Map Ctl PgUp PgDn Next Prev Board IBCONF EXE eps Figure 5 10 Typical National Instruments GPIB Configuration from IBCONF EXE Computer Interface Operation 5 21 Lake Shore Model 625 Superconducting MPS User s Manual Table 5 6 Quick Basic IEEE 488 Interface Program IEEEEXAM BAS EXAMPLE PROGRAM FOR IEEE 488 INTERFACE This program works with Qu
209. the setting sequence 4 8 Operation Lake Shore Model 625 Superconducting MPS User s Manual 4 12 RAMP SEGMENTS Many magnets cannot be charged or discharged at the same rate throughout its entire current capacity Typically the magnet cannot be charged as fast when the current in the magnet is high The Model 625 has a ramp segment feature that can change the output current ramp rate based on the output current setting As the output setting ramps through the segment boundary the new ramp rate will be used although it will still be limited by the maximum ramp rate setting Refer to Paragraph 4 11 3 to set the maximum ramp rate To use the ramp segment feature the ramp segments must be enabled and the ramp segment table must be setup to specify which ramp rate to use for each current setting The table should be setup in order of increasing current A current entry of 0 A indicates the end of the table and the instrument will not search any higher in the table To configure the ramp segments press Ramp Segments The first ramp segments setup screen appears as a prompt for the ramp segments mode Use the A or Y key to select the ramp segments mode either Enable or Disable Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display If the ramp segments are enabled the next ramp segments screen that appears is for entering or editi
210. thods to clear each register are detailed below Table 5 2 Register Clear Methods Register Method Example Condition Registers None registers are not latched Event Registers Standard Event Status Register Operation Event Register Error Status Event Register Query the event register ESR clears Standard Event Status register Send CLS CLS clears both registers Power on instrument Enable Registers Standard Event Status Enable Register Operation Event Enable Register Error Status Enable Register Service Request Enable Register Write 0 to the enable register ESE 0 clears Standard Event Status Enable register Power on instrument Status Byte There are no commands that directly clear the Status Byte as the bits are non latching To clear individual summary bits clear the event register that corresponds to the summary bit Sending CLS will clear all event registers which in turn clears the status byte If bit 5 ESB of the Status Byte is set send ESR to read the Standard Event Status Register and bit 5 will clear Power on instrument Computer Interface Operation 5 7 Lake Shore Model 625 Superconducting MPS User s Manual 5 1 4 2 Status Register Sets As shown in Figure 5 1 there are five register sets in the status system of the Model 625 Standard Event Status Register Operation Event Register Hardware Error Status
211. tive Instrument users have come to rely on Lake Shore for convenience and ease of use The Model 625 includes the features necessary to conveniently manage a superconducting magnet Features such as a persistent switch heater output calculated field reading current ramping and quench detection are all included Computer interfaces are also integrated for automation of the magnet system The Model 625 is truly an excellent one box solution for controlling a superconducting magnet Output Architecture True 4 quadrant output capability of the Model 625 is ideal for the charge and discharge cycling of superconducting magnets for both positive and negative fields Tightly integrated analog control of the 4 quadrant output provides smooth current change with very low overshoot on output change The Model 625 has the ability to charge and discharge magnets up to a 5 V rate True 4 quadrant operation eliminates the need for external switching or operator intervention to reverse the current polarity significantly simplifying system design The transition through zero current is smooth and continuous allowing the user to readily control the magnetic field as polarity changes Introduction 1 1 Lake Shore Model 625 Superconducting MPS User s Manual At static fields output current drift is also kept low by careful attention in the analog control 5 Ampere Charge of an 8 Henry Superconducting Magnet circuits and layout The high stability and low
212. to the current in the magnet Because of this relationship the Model 625 is able to display a calculated field based on a user entered field constant in units of T A or kG A This value is usually supplied by the magnet manufacturer In order to display the field reading the display must be setup to display in field Refer to Paragraph 4 4 1 to setup the display mode Note that the field reading is not an actual measurement of the magnetic field but an approximation calculated by multiplying the measured output current by the field constant To actually measure the magnetic field an external gaussmeter must be used 4 13 1 Field Constant Units The field constant can be entered in either units of T A or kG A This choice not only changes the way the field constant is entered but it also chooses the units of the calculated field as well as the output setting units To set the field constant press Field Constant The first field constant screen appears as a prompt for the field constant units Use the A or V key to select the field constant units either T A or kG A Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display 4 13 2 Field Constant Value The field constant value can be entered in units of T A or kG A depending on what was chosen in the previous step The field constant value will be used to calculate the magnetic field To
213. to the keypad lock mode is not made until the correct keypad lock code has been entered Press Escape to cancel the new selection and return to the normal display 4 16 Operation Lake Shore Model 625 Superconducting MPS User s Manual Once the keypad lock mode has been selected the keypad lock code must be entered to accept the change The following screen appears as a prompt for the keypad lock code Use the data entry keys to enter the 3 digit lock code default 123 An asterisk will appear on the display for each number entered If the code entered matches the lock code the display will show CF x and the keypad lock mode will be updated If the code entered does not match the lock code the display will show Ii E and the keypad lock mode will not change 212 99 4 20 INTERFACE There are two computer interfaces included with the Model 625 a serial interface and an IEEE 488 interface These interfaces are used to connect the instrument to a computer for automated control or data taking Refer to Chapter 5 4 20 1 Changing Serial Baud Rate To select the Serial Interface Baud Rate press the Computer Interface key The first computer interface screen appears as a prompt for Baud Use the A or Y key to select 9600 19200 38400 or 57600 Baud Default is 9600 Baud Press Enter to accept the new selection and continue to the next screen Press Escape to cancel the new selection and return to
214. tor properties Even though a quench is not necessarily destructive to the magnet it should be avoided at all costs Always check the level of liquid helium and make sure that the magnet is completely covered before operating the magnet Never ramp a magnet at a ramp rate greater than what is specified by the magnet manufacturer Never exceed the current rating of the magnet since a quench in this case can easily damage the magnet Typically the current in the magnet will be completely dissipated in about a half of a second causing the magnet to heat It may then take several minutes before the liquid helium cools the magnet back to its superconducting state Since a quench can boil off a significant amount of helium always check the helium level before operating the magnet after a quench Magnet System Design 2 5 Lake Shore Model 625 Superconducting MPS User s Manual Sample a Vent Tube Insert Evacuation Valve Evacuation Valve Helium Reservoir Liquid Helium Level Sensor Isolation Tube Magnet Support Sample Tube Superconducting Magnet Gr So gt EX i ee s E Sample Mount Figure 2 2 Cutaway Of A Typical Helium Dewar Magnet and Insert 2 6 Magnet System Design Lake Shore Model 625 Superconducting MPS User s Manual CHAPTER 3 INSTALLATION 3 0 GENERAL This chapter provides general installation instructions for the Model 625 Superconducting Magnet Power Supply Please read this entire chapter
215. tput current setting when in current display mode press the Output Setting key The output current setting value on the normal display will be highlighted to prompt for the new output current setting value Use the data entry keys to enter an output current setting value between 60 0000 and 60 0000 Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence NOTE The output current setting value can be set as high as 60 1000 A This can be used to compensate for current loss due to high resistance leads and for variances in calibration The output current is guaranteed to reach a minimum of 60 A but may not be able to reach 60 1 A in all circumstances If the display mode is set to field display mode then the output setting value is also in units of field either kG or T Refer to Paragraph 4 13 to setup the field constant and units Even when the output is in units of field the other parameters remain the same The ramp rate is still in units of A s and the maximum current setting is still used There are certain circumstances in which the current will not be allowed to change This is done for safety and to protect the magnet system If the output current is going to be kept from changing an error box will pop up explaining why the new setting is going to be ignored These error boxes are described below Op
216. uce the magnetization M or intrinsic induction in a magnetic material to zero intrinsic induction The contribution of the magnetic material Bi to the total magnetic induction B Bi B poH SD Bi B H cgs isolated neutral system A system that has no intentional connection to ground except through indicating measuring or protective devices of very high impedance Kelvin K The unit of temperature on the Kelvin Scale It is one of the base units of SI The word degree and its symbol are omitted from this unit See Temperature Scale for conversions Glossary of Terminology A 3 Lake Shore Model 625 Superconducting MPS User s Manual Kelvin Scale The Kelvin Thermodynamic Temperature Scale is the basis for all international scales including the ITS 90 It is fixed at two points the absolute zero of temperature 0 K and the triple point of water 273 16 K the equilibrium temperature that pure water reaches in the presence of ice and its own vapor line regulation The maximum steady state amount that the output voltage or current changes as result of a specified change in input line voltage usually for a step change between 105 125 or 210 250 volts unless otherwise specified line voltage The RMS voltage of the primary power source to an instrument load regulation A steady state decrease of the value of the specified variable resulting from a specified increase in load generally from no load to full load u
217. uery ELSE PRINT NO RESPONSE No response to query END IF END IF Get next command GOTO LOOP1 5 30 Computer Interface Operation Lake Shore Model 625 Superconducting MPS User s Manual 5 2 7 3 Program Operation Once either example program is running try the following commands and observe the response of the instrument Input from the user is shown in bold and terminators are added by the program The word term indicates the required terminators included with the response ENTER COMMAND IDN Identification query Instrument will return a string identifying itself RESPONSE LSCI MODEL625 1234567 06122003 term ENTER COMMAND RDGR 1 Ohm reading query Instrument will return a string with the present resistance reading from channel 1 RESPONSE 273 150E 00 term ENTER COMMAND HTRRNG 0 Heater range command Instrument will turn off the heater No response will be sent ENTER COMMAND HTRRNG Heater range query Instrument will return a string with the present heater range setting RESPONSE O term ENTER COMMAND HTRRNG 1 HTRRNG Heater range command followed by a query Instrument will change to heater Low setting then return a string RESPONSE 1 term with the present setting The following are additional notes on using either IEEE 488 Interface program Ifyou enter a correctly spelled query without a nothing w
218. um tin Nb3Sn embedded in a copper matrix The copper matrix is used for mechanical stability and to provide a path for large currents in the case of a magnet quench Typically niobium tin is only used in magnets that can generate fields in excess of 9 Tesla because it is more expensive and harder to work with than niobium titanium Magnet System Design 2 1 Lake Shore Model 625 Superconducting MPS User s Manual The superconducting wire is wound around a non magnetic former made from aluminum brass stainless steel or other material as needed The individual windings are electrically insulated by the insulation on the wire and by an epoxy that is applied to the windings The epoxy is also necessary to keep the individual windings from moving when the magnet is charged h Magnet Current Leads Switch Heater Leads Persistent Switch J Protection Diodes Figure 2 1 Typical Superconducting Magnet 2 2 2 Magnet Inductance The inductance of a solenoid L is defined as L pon A 1 where po is the permeability of air n is the number of turns A is the cross sectional area of the coil and is the length of the solenoid The inductance of superconducting magnets is fairly large typically between 10 and 100 Henries The magnet s inductance limits the rate at which the magnet can be charged or discharged because of the increased voltage required to change current The formula V L di dt relates charging volt
219. up explaining why the new setting is going to be ignored 4 6 Operation Lake Shore Model 625 Superconducting MPS User s Manual 4 7 COMPLIANCE VOLTAGE LIMIT The output compliance voltage limit of the Model 625 can be set between 0 1 and 5 V The setting is in magnitude only and will limit both positive and negative voltages On most superconducting magnets the maximum compliance voltage is usually stated and can vary depending on the current in the magnet Exceeding the maximum compliance voltage of the magnet can cause the magnet to quench The compliance voltage can be limited by setting the maximum compliance voltage setting Refer to Paragraph 4 11 to setup the maximum settings To change the compliance voltage limit press the Voltage Limit key The compliance voltage limit value on the normal display will be highlighted to prompt for the new compliance voltage limit value Use the data entry keys to enter the compliance voltage limit value between 0 1000 and 5 0000 V Press Enter to accept the new value Press Escape to restart the setting sequence and enter a different value Press Escape again to leave the setting sequence 4 8 ZERO OUTPUT CURRENT The Zero Output key on the front panel can be used to set the output current setpoint to 0 A The current output will then begin to ramp down using the current ramp rate This key is equivalent to using the Output Setting key and entering 0 A Refer to Pa
220. urce capable of driving most switch heaters It sources from 10 mA to 125 mA with a setting resolution of 1 mA and selectable compliance voltage of 12 V or 21 V The minimum load that the persistent switch heater can drive is 10 W Persistent mode operation is integrated into the instrument firmware to prevent mis operation of the magnet Interfaces The Model 625 includes IEEE 488 and RS 232C interfaces that provide access to operating data stored parameters and remote control of all front panel operating functions In addition the Model 625 includes a trigger function that is used to start an output current ramp When the trigger is activated either by an external trigger or by computer interface command the power supply will begin ramping to the new setpoint The Model 625 provides two analog outputs to monitor the output current and voltage Each output is a buffered differential analog voltage representation of the signal being monitored The current monitor has a sensitivity of 1 V 10 A while the voltage monitor has a sensitivity of 1 V 2 1 V Display and Keypad The Model 625 incorporates a large 8 line by 40 character vacuum fluorescent display Output current calculated field in tesla or gauss output voltage and remote voltage sense readings can be displayed simultaneously Five LEDs on the front panel provide quick verification of instrument status including ramping compliance fault PSH status and computer interface mode Err
221. utput current Remote Voltage Sense Reading Query RDGRV term voltage term n nnnn voltage Actual voltage measured at the remote voltage sense leads Output Voltage Reading Query RDGV term voltage term n nnnn lt voltage gt Actual output voltage measured at the power supply terminals Ramp Segments Enable Command RSEG lt enable gt term n term lt enable gt Specifies if ramp segments are to be used 0 Disabled 1 Enabled Ramp segments are used to change the output current ramp rate based on the output current Ramp segments need to be setup first using the RSEGS command Ramp Segments Enable Query RSEG term lt enable gt term n Refer to command for description Ramp Segments Parameters Command RSEGS lt segment gt lt current gt lt rate gt term n nn nnnn n nnnn term lt segment gt Specifies the ramp segment to be modified 1 5 lt current gt Specifies the upper output current setting that will use this segment 0 0000 60 1000A lt rate gt Specifies the rate at which the current will ramp at when the output current is in this segment 0 0001 99 999 A s Ramp segments are used to change the output current ramp rate based on the output current The ramp segment feature needs to be turned on using the RSEG command Ramp Segments Parameters Query Input RSEGS lt segment gt term Returned lt current gt lt rate gt term Format nn nnn
222. voltage selector Verify the fuse value and drawer whenever the line voltage is changed WARNING To avoid potentially lethal shocks turn off the power supply and disconnect it from AC power before performing this procedure Identify the line input assembly on the instrument rear panel See Figure 7 2 Turn the front panel line power switch OFF O Remove the instrument power cord With a small screwdriver release the drawer holding the line voltage selector and fuses Slide out the removable line voltage selector from the drawer Rotate the line voltage selector until the proper voltage indicator shows through the window Verify the proper fuse value and fuse drawer Re assemble the line input assembly in the reverse order SOOO at Gy CA decus A Verify the voltage indicator in the window of the line input assembly Connect the instrument power cord Rh _ Turn the front panel line power switch On I 7 2 Service Lake Shore Model 625 Superconducting MPS User s Manual _ Fuse Drawer 220 240 V 5 0 AT 250V 5X20mm 100 120 220 240 V ELE 100 120 V 10 0A T 250 V 0 25X1 25 N Screwdriver Slot Line Cord Input Line Input bmp Figure 7 2 Power Fuse Access 7 5 FUSE REPLACEMENT Use the following procedure to remove and replace the line fuses WARNING To avoid potentially lethal shocks turn off the power supply and disconnect it from AC power before performing these procedure
223. with adequate ventilation DO NOT vent container in confined spaces DO NOT enter confined spaces where gas may be present unless area has been well ventilated If inhaled remove to fresh air If not breathing give artificial respiration If breathing is difficult give oxygen Get medical help WARNING Liquid helium and liquid nitrogen can cause severe frostbite to the eyes or skin DO NOT touch frosted pipes or valves In case of frostbite consult a physician at once If a physician is not readily available warm the affected areas with water that is near body temperature The two most important safety aspects to consider when handling LHe and LN are adequate ventilation and eye and skin protection Although helium and nitrogen gases are non toxic they are dangerous in that they replace the air ina normal breathing atmosphere Liquid products are of an even greater threat since a small amount of liquid evaporates to create a large amount of gas Therefore it is imperative that cryogenic dewars be stored and the cryogenic system be operated in open and well ventilated areas Persons transferring LHe and LN should make every effort to protect eyes and skin from accidental contact with liquid or the cold gas issuing from it Protect your eyes with full face shield or chemical splash goggles Safety glasses even with side shields are not adequate Always wear special cryogenic gloves Tempshield Cryo Gloves or equivalent when handling anything
224. with the Error Status Registers The Error Status Enable command ERSTE programs the enable register and the query command ERSTE reads it ERSTR reads and clears the Error Status Register The used bits of the Error Status Event Register are described as follows Magnet Discharging Through Crowbar MDC Bit 6 This bit is set to indicate that the magnet is currently discharging through the crowbar This can happen due to a hardware error or a power loss Magnet Quench Detected QNCH Bit 5 This bit is set to indicate that a magnet quench has been detected Remote Inhibit Detected OCF Bit 4 This bit is set if the remote inhibit condition has been detected Temperature High OOV Bit 3 This bit is set if the internal temperature of the instrument exceeded 75 C The current ramp will be stopped or the compliance voltage will be limited in an attempt to lower the internal temperature High Line Voltage HLV Bit 2 This bit is set if the power line voltage exceeds an acceptable amplitude Operation can continue but additional heat may be dissipated by the instrument External Current Program Error EPE Bit 1 This bit is set if the instrument cannot go into external or sum current programming modes because the programming voltage is too high Calibration Error CAL Bit 0 This bit is set if the instrument is not calibrated or the calibration data has been corrupted 5 10 Computer Interface Oper
225. wn below as well as to the right of the field reading This includes the output field setting the current ramp rate the output current reading the output current setting the output voltage reading the compliance voltage limit and the remote voltage sense reading Display setup is described in Paragraph 4 4 Figure 4 2 Model 625 Magnet Field Display 4 2 3 Persistent Switch Heater Display The lower right corner of the display shows the status of the persistent switch heater if the persistent switch is enabled It will indicate if the heater is off on warming or cooling If the heater is on it will also display the heater current This area of the display will be blank if the persistent switch heater is disabled Refer to Paragraph 4 14 for information on setting up the Persistent Switch Heater Output 4 2 4 LED Annunciators There are five LED annunciators on the front panel that are used to indicate the status of the instrument These are to provide easy verification of the operation of the instrument Fault On when a hardware fault condition exists blinking when a soft fault condition exists Compliance On when output is in voltage compliance Ramping On when output current is ramping blinking when ramp is paused PSH On On when persistent switch heater is on blinking when the heater is warming or cooling Remote On when instrument is in remote computer interface mode 4 3 KEYPAD DEFINITION The Model 625 has 26 k
226. y to establish communication with the instrument or intermittent failures in communication 5 2 7 Serial Interface Example Programs Two BASIC programs are included to illustrate the serial communication functions of the instrument The first program was written in Visual Basic Refer to Paragraph 5 2 7 1 for instructions on how to setup the program The Visual Basic code is provided in Table 5 9 The second program was written in Quick Basic Refer to Paragraph 5 2 7 2 for instructions on how to setup the program The Quick Basic code is provided in Table 5 10 Finally a description of operation common to both programs is provided in Paragraph 5 2 7 3 While the hardware and software required to produce and implement these programs not included with the instrument the concepts illustrated apply to almost any application where these tools are available 5 26 Computer Interface Operation 5 2 7 1 Lake Shore Model 625 Superconducting MPS User s Manual Visual Basic Serial Interface Program Setup The serial interface program works with Visual Basic 6 0 VB6 on an IBM PC or compatible with a Pentium class processor A Pentium 90 or higher is recommended running Windows 95 or better with a serial interface It uses the COMI communications port at 9600 Baud Use the following procedure to develop the Serial Interface Program in Visual Basic Start VB6 Choose Standard EXE and select Open Resize form window to desired size On the Pr
227. ype gt lt value gt term Format nn nnnnnnn lt type gt Specifies the item to calibrate Valid entries are 0 Output Current Reading 1 Bias A Reading 2 Bias B Reading 3 CM Voltage Reading 4 Out Control Reading 5 Output Voltage Reading 6 Remote Voltage Reading 7 External Programming Voltage 8 Temperature 9 Raw Supply Voltage 10 Actual Output Current value Zero offset calibration constant value Remarks Items marked with a are for internal diagnostic use only and should always be set to a value of 0 default CALZ Zero Offset Calibration Constant Query Input CALZ lt type gt term Format nn type 1 10 Returned lt value gt term Format nnnnnnn Refer to command for description 7 20 Service Lake Shore Model 625 Superconducting MPS User s Manual APPENDIX A GLOSSARY OF TERMINOLOGY accuracy The degree of correctness with which a measured value agrees with the true value electronic accuracy The accuracy of an instrument independent of the sensor sensor accuracy The accuracy of a temperature sensor and its associated calibration or its ability to match a standard curve American Standard Code for Information Exchange ASCII A standard code used in data transmission in which 128 numerals letters symbols and special control codes are represented by a 7 bit binary number as follows OJON DU Aa Njej w oO o ja ou 5 a

Lake Shore Model 625 Superconducting Magnet Power Supply

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