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Analog PID Controller - Stanford Research Systems

1. ICTL z 3 10 Integral action ON OFF INCR i 3 19 Instrument condition register INPT z 3 12 Input Internal External Setpoint INSE i 3 19 Instrument status enable register INSR i 3 19 Instrument status register INTG f 3 11 Integral Gain L LBTN 3 23 Last Button LCME 3 23 Command Error LEXE 3 22 Execution Error LLIM f 3 14 Lower Output Limit M MMON i 3 14 Measure Input Monitor MOUT f 3 13 Manual Output O OCTL z 3 10 Offset ON OFF OFST f 3 11 Output Offset OMON i 3 15 Output Monitor P PARI z 3 17 Parity PCTL z 3 10 Proportional action ON OFF PSTA z 3 20 Pulse STATUS Mode R RAMP z 3 12 Internal setpoint ramping ON OFF RATE f 3 12 Setpoint ramping Rate RFMT 2 3 15 Output Streaming Records Format RMPS 3 13 Setpoint ramping status S SETP f SHFT z SMON i SOUT z STRT z 3 12 3 16 3 14 3 16 3 13 New setpoint Shift Status Setpoint Input Monitor Stop Streaming Pause or continue ramping T TERM z 3 24 Response Termination SIM960 Analog PID Controller ASRS Remote Operation TOKN z 3 24 Token Mode U ULIM f 3 13 Upper Output Limit W WAIT i 3 22 Wait ASRS SIM960 Analog PID Controller 3 3 Introduction 3 3 Introduction Remote operation of the SIM960 is through a simple command lan guage documented in this chapter Both set and query fo
2. e Record the process response in the Measure signal Define the dimensionless process step response function M t ht easure t Measure 0 A e Observe the point of maximum slope in h Extend a straight line through this point tangent to h downward see Figure 2 2 e Let L be the time coordinate where the straight line crosses h 0 and let a be the negative of the h intercept i e a gt 0 in Figure 2 2 e Note that it is not necessary to wait for the process to completely settle following the step change A it is sufficient to simply wait until the maximum slope is observed in Measure From a and L Ziegler and Nichols suggest tuning for P PI and PID control as shown in Table 2 1 Control P I D P 1 a PI 0 9 a 1 3L PID 12 a 1 2L L 2 Table 2 1 Ziegler Nichols open loop tuning parameters Ziegler J G amp Nichols N B 1942 Trans ASME 64 759 SIM960 Analog PID Controller j SRS 2 6 Advanced Topics AN Meas Meas 0 h t Figure 2 2 The open loop step response of the process 2 2 2 Closed loop tuning An alternate method also due to Ziegler and Nichols is based on measuring the gain at which the process just begins to oscillate The procedure is e Switch the SIM960 into PID mode with I and D both disabled Choose a value for Setpoint around the desired operating point and set P so some small value e Slowly increas
3. 4 SRS SIM960 Analog PID Controller 2 Advanced Topics In This Chapter This chapter discusses a simple closed loop tuning procedure along with some of the advanced features of the SIM960 Analog PID Controller 2 1 PID Tuning Basics 53 ira 2 2 2 2 Ziegler Nichols Tuning 2 5 2 2 1 Open loop tuning 2 5 222 Closed loop tuning 2 6 23 Anti Windup and Conditional Integration 2 7 24 Bumpless Transfer 4444114111 2 8 241 Manual to PID ss Vect SEG se 2 8 2 4 2 PID to Manual oss 2022 3I 2 8 2 2 Advanced Topics 2 1 PID Tuning Basics PID control provides a simple way to minimize the effect of dis turbances to a system The system consists of a closed feedback loop between two elements the SIM960 controller and the user pro cess The controller has two inputs Setpoint and Measure and an Output The process consists of a power source that can be directly changed by the controller in conjunction with a sensor to monitor the process behavior The sensor signal after any necessary condition ing is the process output This should be connected to the Measure input of the SIM960 and the SIM960 Output should be connected to the process input forming a feedback loop The difference between the Setpoint and Measure inputs is the error signal Setpoint Measure Eqn 1 1 In the SIM960 the error signal is amplified by the proportional gai
4. C740 5 00059 051 47U R808 R810 R814 R815 4 01486 100 2 0K C741 C742 5 00098 030 10U R817 R826 4 01111 110 866 C811 C821 C903 C904 C906 5 00102 030 4 7U R821 4 01038 110 150 C834 5 00377 100 150P R837 R840 R842 4 00913 000 49 9 FP D802 D801 3 01430 BAS40 05 R844 R847 4 01142 110 1 82K D804 D803 3 00901 145 BAS40 06 R863 4 01309 110 100K D808 D807 3 01487 12V zener R865 R864 4 00219 000 20 00K J505 J506 J701 J804 J805 1 00073 Insulated BNC U501 3 01358 122 DG444 J901 1 01015 30 PIN 3x10 M U504 U506 U513 U605 3 01361 120 OPA2228 K502 3 00308 203 DS2E ML2 DC5V U505 U508 U606 3 01363 171 LTC1590 Q504 Q505 Q802 3 00927 150 MMBT2907A U509 3 01364 120 OPA4277 Q801 3 01421 150 MMBT2222 U514 U512 3 01360 120 OPA228 R502 R507 R542 R547 4 01175 110 4 02K U601 3 01365 122 DG411DY R510 R533 R534 R819 4 01146 110 2 00K U702 U602 3 01366 122 DG333ADW R527 4 01158 110 2 67K U603 U604 U807 3 01367 122 DG419DY R528 4 01149 110 2 15K U701 U607 3 01398 OPA2131 R530 4 01204 110 8 06K U608 3 01386 122 DG408DY R531 4 01262 110 32 4K U609 3 01361 120 OPA2228 R535 R536 R538 R539 R641 4 01242 110 20 0K U610 3 01431 LTC1595 R642 R816 R829 U611 U708 U720 U809 3 00952 120 OPA2277 R541 R566 4 00012 053 20K U703 3 01369 122 DG409 SO R544 R549 R553 R558 4 01649 000 1 000K U808 U707 3 01372 171 LTC1596 1 R545 R556 R710 R839 R860 4 01405 110 1 00M U709 3 01374 103 74HC132A R548 4 01418 100 3 U710 3 00742 103 74HC74 R550 4 01614 053 10 U711 3 01375 103 74HC86 R551 R617 R709 R713
5. STB i Example Status Byte Reads the Status Byte register bit Execution of the STB query without the optional bit i always causes the STATUS signal to be deasserted Note that STB i will not clear STATUS even if bit is the only bit presently causing the STATUS signal STB 16 SRE i i Example Service Request Enable Set query the Service Request Enable register bit i to j SRE 32 SRE 5 1 ESR i Example Standard Event Status Reads the Standard Event Status Register bit i Upon executing ESR the returned bit s of the ESR register are cleared GAIN 0 ESR 16 The binary value 16 corresponds to an Execution Error since GAIN 0 is an illegal value minimum gain is 0 1 ESE i U Example Standard Event Status Enable Set query the Standard Event Status Enable Register bit i to j ESE 16 CESR i Example Comm Error Status Query Comm Error Status Register for bit i Upon executing a CESR query the returned bit s of the CESR register are cleared CESR 0 ASRS SIM960 Analog PID Controller 3 4 Commands CESE 1 101 Example Comm Error Status Enable Set query Comm Error Status Enable Register bit i to j CESR 0 INCR i Example Instrument condition register Query the instrument condition register bit i The values of the bits in the instrument condition register ar
6. 0 0 ANTIWIND 3 H 3 3 ADSR ADSE LuMm 2 2 H2 ULIMIT 1 1 1 ov o o H o o Standard Event Status URQ User Request 6 CME Command Error EXE Execution Error DDE Device Error QYE Query Error INP Input Buffer Error Und OPC Operation Complete 0 Analog to Digital Status Communication Error Status DCAS Device Clear 7 CTSH CTS Halted 6 RTSH RTS Halted 5 OVR Input Buffer Overrun 4 HWOVRN Hardware Overrun 3 2 1 0 ESR NOISE Noise Error FRAME Framing Error PARITY Parity Error nlwjajuja u PON Power On HgH 6 0 CESE 4 Status Byte ESR ESE INCR INSR INSE Figure 3 1 Status Register Model for the SIM960 Analog PID Con troller There are three categories of registers in the SIM960 status model Condition Registers Event Registers Enable Registers These read only registers correspond to the real time condi tion of some underlying physical property being monitored Queries return the latest value of the property and have no other effect Condition register names end with CR These read only registers record the occurrence of defined events If the event occurs the corresponding bit is set to 1 Upon querying an event register any set bits withi
7. 12 ADC measurement of PID Manual Output DISP 1 SHFT 2 Example Shift Status Set query the current shift status to i OFF 0 ON 1 SHFT OFF ASRS SIM960 Analog PID Controller 3 4 Commands DISX z Example Front Panel Display Enable Set query the front panel display status to Z OFF 0 ON 1 When the display is turned off DISX OFF all front panel indicators and buttons are disabled DISX OFF 3 4 7 Serial communication commands BAUD i Example Baud Rate Set query the baud rate to i At power on the baud rate defaults to 9600 Changing baud rate must be carefully orchestrated to ensure proper connectivity throughout the transaction see the SIM900 manual discussion of the BAUD command for more examples BAUD 38808 FLOW z Example Flow Control Set query flow control to Z NONE 8 RTS 1 XON 2 At power on the SIM960 defaults to FLOW RTS flow control FLOW 9 PARI z Example 3 4 8 Status commands Parity Set query parity to z NONE 0 ODD 1 EVEN 2 MARK 3 SPACE 4 At power on the SIM960 defaults to PARI NONE PARI NONE The Status commands query and configure registers associated with status reporting of the SIM960 CLS Example Clear Status CLS immediately clears the ESR CESR and the SIM960 status reg isters CLS SIM960 Analog PID Controller SRS Remote Operation
8. based on real time measurements from the onboard A to D converter Connect the sensor output of the system to be controlled to the Mea sure input of the SIM960 f an external setpoint is to be supplied con nect this to the Setpoint input and use the button in the INPUTS section of the front panel to select External input Before connect ing the SIM960 output to the system to control it may be necessary to set the user programmable output upper and lower Limits to guard against damaging the system Care should be taken to insure that the programmed output range is consistent with the system input range Once the limits have been programmed connect the SIM960 output to the system input SIM960 Analog PID Controller fs RS 1 6 Getting Started 1 2 4 Bar displays Two LED bar displays have been included on the right side of the SIM960 front panel to provide visual information about the P x and Output signals This reduces the need to frequently return to those fields on the numerical display while trying to adjust other tuning parameters Some time should be taken to understand what information these bar displays provide Each bar has two lighted LEDs one for the maximum peak of the signal and one for the minimum peak The peaks are determined with respect to time variation of the signal and they decay back to the DC level with a decay time of 100 ms To understand how a signal is represented in the bar display c
9. is presently occurring in the front end amplifier ULIMIT Upper Limit Reached Set to indicate the output signal is presently saturated into the programmable upper limit volt age LLIMIT Lower Limit Reached Set to indicate the output signal is presently saturated into the programmable lower limit volt age ANTIWIND Anti windup Active Set to indicate the anti windup circuit is actively inhibiting integration of the error signal RSTOP Ramp Stopped Set to indicate that no internal setpoint ramp is in progress cleared to indicate ramping is presently underway Instrument Status INSR The Instrument Status Register consists of latching event flags that correspond one to one with the bits of the INCR see above Upon the transition 0 gt 1 of any bit within the INCR the corresponding bit in the INSR becomes set Bits in the INSR are unaffected by the 1 0 transitions in the INCR and are cleared only by reading or with the CLS command Reading a single bit with the INSR i query clears only bit i 3 5 9 Analog to Digital Status Enable INSE The INSE acts as a bitwise AND with the INSR register to produce the single bit INSB message in the Status Byte Register SB It can be set and queried with the INSE command This register is cleared at power on 3 5 10 Analog to Digital Status ADSR The Analog to Digital Status Register consists of 4 event flags each of which is set by a corresponding con
10. the topology of the SIM960 design feedback polarity can be changed simply by changing the polarity of the proportional gain parameter P The user must first determine which polarity will provide negative feedback If the ASRS SIM960 Analog PID Controller 21 PID Tuning Basics 2 3 Internal Setpoint Ramp Generator External PE tpoint ma E Monitor Output rear panel BNC Measure Input ee SP M ye Selector Output P x fe Ife dt p Offset D Output Output Buffer w User i Controlled Limits Antiwindup circuitry see text oter Bumpless transfer when is enabled Control Figure 2 1 The SIM960 block diagram process is noninverting i e a small positive change at its input results in a positive change at its output then using positive P polarity will ensure negative feedback in the loop To see this follow the effect of a small positive change at the process output Since the process output is connected to the Measure input of the SIM960 a small positive change would cause a negative change to e The resulting change at the controller Outputwould also be negative as would be that of the process output Thus the initial small positive change at the process output is corrected by a negative change after going around the feedback loop As a general rule if the process is noninverting then the P polarity should be positive If the process is inverting negative P po
11. to manual mode will also be smooth With the module in PID mode select the Manual field Press On Off and hold it down for at least one second After one second the manual display reading will shift to the current PID output level The output mode will remain in PID control mode until it is manually switched on the front panel or through the remote interface But the new manual output level will be equal to the PID control output 3 This can be understood mathematically since only the integral term has an un specified initial offset value that can be set to an arbitrary value without violating Eqn 1 2 ASRS SIM960 Analog PID Controller 3 Remote Operation In This Chapter This chapter describes operating the module over the serial interface 3 1 3 2 3 3 3 4 3 5 Index of Common Commands 3 2 Alphabetic List of Commands 3 4 Introduction ip ss NUN IUS Eo 3 7 3 3 1 Power on configuration 3 7 332 Buffers ia eo black ene Sle Gases 3 7 3 3 3 DeviceClear llle n 3 7 Commands 4 e dnde UR Ee e 3 8 3 4 1 Command syntax eR Ra 3 8 3427 Examples S so Re du cx Oe RYE 3 9 3 4 3 Controller settings commands 3 10 3 4 4 Controller configuration commands 3 12 3 4 5 Monitor commands 3 14 3 4 6 Displaycommands 3 16 3 4 7 Serial communication commands 3 17 3 48 Status commands 1 44441411 3 17 3 4 9 In
12. 03 3 00751 103 74HC574 R320 R322 R324 R326 R328 U401 3 01424 061 HDSP A107 R330 R332 U402 U403 U404 U405 U406 3 00290 061 HDSP A101 R111 R114 R118 R123 R151 4 01503 100 10K R152 R153 R154 R155 R276 X101 X314 41 total 5 00299 100 1U R334 Y101 6 00571 020 10 000MHZ R112 R113 R122 4 01527 100 100K Y104 Y108 Y202 Y203 Y204 4 01213 110 10 0K R115 R117 R119 4 01465 100 270 Y206 Y207 Y208 Y210 Y211 R128 R242 4 01309 110 100K Y229 Y252 Y253 Y256 Y258 R201 R205 R209 R212 R233 4 01405 110 1 00M Y261 Y282 Y283 Y284 Y285 R235 R237 R239 R282 R286 PCB SIM960 Digital Board 7 01258 SIM960 Analog PID Controller ASRS 5 6 Circuitry 5 2 2 Analog Board Part Reference SRS P N Value Part Reference SRS P N Value C502 C504 C506 C507 C536 5 00365 100 15P R702 4 01050 110 200 C537 C538 C541 C608 C637 R704 4 01195 110 6 49K C638 R708 4 01287 110 59 0K C511 C521 C618 C708 C816 5 00369 100 33P R711 R712 R719 R720 R761 4 01088 110 499 C602 C702 C832 5 00026 100 22P R803 R809 R811 C603 C616 C712 5 00072 050 10U R723 R724 R725 R726 R740 4 00218 000 10 00K C610 5 00025 100 100P R744 R866 C611 5 00442 120 001U R746 4 00011 053 10K C612 5 00454 120 01U R748 4 00014 053 5K C613 5 00466 120 1U R748 4 00014 053 5K C614 5 00538 050 1 0U R760 4 01128 110 1 30K C640 5 00350 56U R763 R762 4 01021 110 100 C641 5 00582 033U R764 4 01169 110 3 48K C642 5 00048 050 0015U R765 4 01455 100 100 C643 5 00583 100P R804 R812 4 01551 100 1 0M
13. 49 9K D467 D468 D469 D470 D471 R283 R285 4 01288 110 60 4K D201 D202 D203 D204 3 01430 143 BAS40 05 R284 R287 4 01088 110 499 D205 3 01409 145 BAV99DW R288 R289 4 01271 110 40 2K D401 D420 3 00424 060 GREEN R301 R302 R303 R304 R305 4 01459 100 150 D421 D422 D424 D427 D428 R306 R307 R308 D429 D443 R309 R310 R311 R312 R313 4 01462 100 200 D444 D445 D446 D448 D449 R314 R315 R316 D450 D451 D452 D453 D454 R319 R321 R323 R325 R327 4 01496 100 5 1K D455 D456 D457 D458 D459 R329 R331 R333 D460 D461 D462 401 S402 S403 S404 S405 2 00053 000 B3F 1052 D426 D447 D463 3 00425 060 RED 5406 5407 5408 JP101 1 00302 010 6 PIN DIF CES U101 3 00903 124 MAX6348 JP103 1 00367 040 15 PIND U102 3 01378 103 74HCU04 JP104 1 00086 002 3 PIN SI U103 3 01379 114 68HC912B32 J202 1 01014 30 PIN 3x10 F U104 3 00662 103 74HC14 J301 1 00593 009 HEADER SIL26 U201 U202 3 01380 120 LF444CM J401 1 00594 019 HEADER SIF26 U203 U212 3 00731 120 5534 L102 L103 L105 6 00174 051 BEAD U204 3 01386 122 DG408 L301 6 00236 130 BEAD U205 3 01425 170 LTC2415CGN Q201 3 00927 150 MMBT2907ALT1 U206 3 01383 123 REF02 Q301 Q316 3 01421 150 MMBT2222 U207 3 00663 103 74HC08 R101 4 01495 100 4 7K U208 3 00116 030 78L05 R102 R106 4 01479 100 1 0K U209 3 00952 120 OPA2277 R103 4 01431 100 10 U210 3 00727 121 LM339 R105 4 01511 100 22K U211 3 00724 120 LF353 R107 4 01057 110 237 U213 3 00728 121 LM393 R109 4 01405 110 1 00M U301 3 01433 103 74HC259 R110 R116 R120 R121 R318 4 01455 100 100 U302 U3
14. 960 PID Controller allows the user to linearly slew the internally generated setpoint level from its current value to a new value The slew rate may be changed using the SP Ramp parameter on the front panel The indicator to the right of SP Ramp shows whether ramp ing is enabled or disabled Use On Off with SP Ramp se lected to enable disable ramping When disabled changes to the Internal Setpoint parameter take effect immediately When ramping is enabled however changes to Internal Setpoint do not immediately take effect Instead Internal in the Setpoint block of the INPUTS section of the front panel begins to blink showing that a new setpoint has been entered and a ramp event is now pending To begin the ramp press Ramp Start Stop Now the Internal blink rate doubles indicating that the setpoint is ramping To pause the ramp press Ramp Start Stop When the ramp is paused the In ternal blink rate becomes uneven To continue the ramp press Ramp Start Stop again When the setpoint reaches the new pro grammed value the ramp automatically terminates and Internal stops blinking Note SP Ramp has no sign in the numerical display This is be cause the polarity of the ramp rate is unambiguously determined by whether the newly entered setpoint is greater or less than the current setpoint The range of available ramp rates is from 1 mV s to 10 000 V s For ramp rates less than or equal to 1 V s the rate is dynamically trimmed
15. F gt SIM 10 MHz reference optional connection 13 5V MF gt SIM Power supply digital circuitry 14 15V MF gt SIM Power supply analog circuitry 15 24V MF gt SIM Power supply no connection in SIM960 1 4 2 Direct interfacing Table 1 1 SIM Interface Connector Pin Assignments DB 15 The SIM960 is intended for operation in the SIM900 Mainframe but users may wish to directly interface the module to their own systems without the use of additional hardware ASRS SIM960 Analog PID Controller 14 SIM Interface 1 9 The mating connector needed is a standard DB 15 receptacle such as Amp part 747909 2 or equivalent Clean well regulated supply voltages of 5 15 VDC must be provided following the pin out specified in Table 1 1 Ground must be provided on Pins 1 and 8 with chassis ground on Pin9 The STATUS signal may be monitored on Pin 2 for a low going TTL compatible output indicating a status message 1 4 2 1 Direct interface cabling If the user intends to directly wire the SIM960 independent of the SIM900 Mainframe communication is usually possible by directly connecting the appropriate interface lines from the SIM960 DB 15 plug to the RS 232 serial port of a personal computer Connect RXD from the SIM960 directly to RD on the PC TXD directly to TD and similarly RIS RIS and CTS CTS In other words a null modem style cable is not needed To interface directly to the DB 9 male DTE
16. HZ signal if present on JP103 The front panel display is illuminated by successively strobing eight digital lines from U301 Each strobe line consists of an NPN emitter follower Q301 through Q308 that energizes one seven segment dis play chip and a set of eight LEDs in parallel The eight cathodes from the segment display are held high or low at U302 based on a pattern from the controller Similarly U303 controls the eight lines from the LED cathodes using NPN open collectors Q309 through Q316 as output current buffers The Measure and Setpoint single ended inputs of the SIM960 are differenced to form the error signal with a standard three op amp instrumentation amplifier U512 U513 operating at 9x gain R544 R549 R553 amp R558 are high stability resistors 0 1 5 ppm C used to reduce offset drift and to improve common mode rejection CMRR R550 is a 10 O trimpot for trimming the CMRR Polarity control is implemented at U514 which switches between gain 1x and 1x with U501A Next U505B is a 12 bit multiplying D to A converter DAC which together with U504 is used as a vernier attenuator in the error am plifier Finally there are three inverting amplifiers in series each of which may be switched between gain 1x and some larger gain The three amplifier gains 16x 4X and 2X allow the total amplifier gain to be switched by factors of two up to approximately 128x The order of the amplifiers large
17. OPC writes a 1 in the Output Queue when com plete but does not affect the ESR register OPC 1 WAIT i Example Wait Wait i milliseconds before processing more commands from the host When using the WAIT command be careful to not overflow the input buffer of the SIM960 see section 3 3 2 SETP 0 RATE 0 1 SETP 1 0 WAIT 5000 SMON 00 483159 LEXE Example Execution Error Query the last execution error code Valid codes are Value Definition 0 No execution error since last LEXE 1 Illegal value 2 Wrong token 3 Invalid bit 16 Invalid parameter 17 Missing parameter 18 No change 20 Ramp in progress 21 Limits conflict STB 12 LEXE LEXE 3 0 The error 3 Invalid bit is because STB only allows bit specific queries of 0 7 The second read of LEXE returns 0 ASRS SIM960 Analog PID Controller 3 4 Commands LCME Command Error Query the last command error code Valid codes are Value Definition 0 No execution error since last LCME 1 Illegal command 2 Undefined command 3 Illegal query 4 Illegal set 5 Missing parameter s 6 Extra parameter s 7 Null parameter s 8 Parameter buffer overflow 9 Bad floating point 10 Bad integer 11 Bad integer token 12 Bad token value 13 Bad hex block 14 Unknown token Example IDN LCME 4 The error 4 Illegal set is due to the missing LBTN Last But
18. Operation and Service Manual Analog PID Controller SIM960 SRS Stanford Research Systems Revision 2 3 e October 10 2013 Certification Stanford Research Systems certifies that this product met its published specifications at the time of shipment Warranty This Stanford Research Systems product is warranted against defects in materials and workman ship for a period of one 1 year from the date of shipment Service For warranty service or repair this product must be returned to a Stanford Research Systems authorized service facility Contact Stanford Research Systems or an authorized representative before returning this product for repair Information in this document is subject to change without notice Copyright Stanford Research Systems Inc 2003 2013 All rights reserved Stanford Research Systems Inc 1290 D Reamwood Avenue Sunnyvale CA 94089 USA Phone 408 744 9040 e Fax 408 744 9049 www thinkSRS com e e mail info thinkSRS com Printed in U S A Document number 9 01558 903 4 SRS SIM960 Analog PID Controller Contents General Information Safety and Precautions for Use MD sc ot AA cine exeo e eee Rake es Pt cns Notation zc elo RR Aa SPECUICANODAC sc ark 1 Getting Started 1 1 General ze eee oe OR OE we W Us 1 2 Front Panel Operation 1 3 Rear Panel Monitoring 1 4 SIMInterface 0 0 200005 2 Adv
19. R721 4 01117 110 1 00K U712 U802 U803 U805 3 00813 121 LM311M R862 U823 U730 3 01488 AQY221R2S R557 R554 4 01067 110 301 U731 3 01387 120 LT1097S8 R559 R563 R564 R565 4 00925 110 10 U732 3 00133 OPA131 R560 R561 R562 R718 R747 4 01184 110 4 99K U804 3 00744 103 74HC151 R806 R813 R823 R824 U820 3 01370 120 OPA277UA R602 R614 R615 R619 R628 4 01163 110 3 01K U821 3 00998 120 OPA227UA R845 R846 U822 3 00279 340 LT1010CN8 R616 4 01317 110 121K U901 3 01432 OPA4131 R618 R620 R621 R622 R623 4 01561 100 2 7M U903 U902 3 00787 103 74HC595 R624 R717 R805 X509 X910 90 total 5 00299 100 1U R644 R643 4 00997 110 56 2 Y537 Y827 16 total 4 01213 110 10 0K R645 R646 R647 R648 4 01503 100 10K PCB SIM960 Analog Board 7 01259 SRS SIM960 Analog PID Controller 53 Schematic Diagrams 5 3 Schematic Diagrams Schematic diagrams follow this page SIM960 Analog PID Controller ASRS
20. RS 232 port typically found on contemporary personal computers a cable must be made with a female DB 15 socket to mate with the SIM960 and a female DB 9 socket to mate with the PC s serial port Separate leads from the DB 15 need to go to the power supply making what is sometimes know as a hydra cable The pin connections are given in Table 1 2 DB 15 F to SIM960 Name DB 9 F 3 gt 7 RTS 4 8 CTS 10 3 TxD 11 2 RxD 5 Computer Ground to P S 7 gt 15VDC 14 15 VDC 13 5 VDC 89 Ground P S return current 1 Signal Ground separate wire to Ground Table 1 2 SIM960 Direct Interface Cable Pin Assignments Although the serial interface lines on the DB 15 do not satisfy the minimum voltage levels of the RS 232 standard they are typically compatible with desktop personal computers SIM960 Analog PID Controller JE RS 1 10 Getting Started 1 4 2 2 Serial settings The initial serial port settings at power on are 9600 Baud 8 bits no parity 1 stop bit and RTS CTS flow control These may be changed with the BAUD FLOW or PARI commands The maximum standard baud rate that the SIM960 supports is 38400 The minimum baud rate is 110 Above 38400 the SIM960 can be set to the following non RS 232 standard baud rates 62500 78125 104167 156250 Note that these rates are typically not accessible on a standard PC RS 232 port but can be used between the SIM960 and the SIM900 Mainframe
21. US Mode Interface RST 3 20 Reset CONS z 3 21 Console Mode IDN 3 21 Identify TST 3 21 Self Test OPC 3 22 Operation Complete WAIT i 3 22 Wait LEXE 3 22 Execution Error LCME 3 23 Command Error LBTN 3 23 Last Button TOKN 2 3 24 Token Mode TERM z 3 24 Response Termination SIM960 Analog PID Controller SRS 3 4 Remote Operation 3 2 Alphabetic List of Commands CLS ESE 4 Ul ESR i IDN OPC RST SRE i j STB i TST 3 17 Clear Status 3 18 Standard Event Status Enable 3 18 Standard Event Status 3 21 Identify 3 22 Operation Complete 3 20 Reset 3 18 Service Request Enable 3 18 Status Byte 3 21 Self Test A ADSE i tj ADSR i AMAN z APOL z 3 19 A to D status enable register 3 19 A to D status register 3 12 Output Manual Output PID Control 3 11 Controller Polarity B BAUD i 3 17 Baud Rate C CESE i tj CESR i CONS z 3 19 Comm Error Status Enable 3 18 Comm Error Status 3 21 Console Mode D DCTL z 3 10 Derivative action ON OFF 3 11 Derivative Gain 3 16 Select Field 3 17 Front Panel Display Enable EMON i 3 15 Amplified Error Monitor F FLOW z FPLC i 3 17 Flow Control 3 16 Frequency of Power Line Cycle G GAIN f 3 10 Proportional Gain ASRS SIM960 Analog PID Controller 3 2 Alphabetic List of Commands
22. V and are displayed in fixed decimal format For exponential format the mantissa may be changed using the up down arrow buttons The active digit may be selected using the left right buttons shift followed by up down button SIM960 Analog PID Controller ASRS Getting Started 1 2 1 Inputs Polarity gt The right most digit after E is the power of ten exponent For example the display ICE 3 1200 e The P parameter has a selectable indicator before the mantissa This allows the polarity of the controller to be tog gled by the user All other exponentially displayed parameters are unipolar so no sign is displayed for these parameters e In fixed decimal format a value between 10 and 10 may be selected using AY and Shift e The two outputs P x e and Output are accompanied by bar displays on the right side of the front panel P x e simply ranges from 10 V to 10 V However since the controller out put ranges between the user programmed upper and lower limits the output bar display is normalized to that range For example if the limits were set to 5 V and 1 V the full range of the bar display would be 6 V and 0 V would no longer cor respond to the center of the bar display but would be 1 6th of the way up from the bottom The default limits are 10 V e Use Setpoint in the INPUTS section of the front panel to choose between an external setpoint input and the internally generate
23. anced Topics 21 PID Tunmg B sies xoxo RS Goole RSS REUS 2 2 Ziegler Nichols Tuning 2 3 Anti Windup and Conditional Integration 24 Bumpless Transfer ooo oo 3 Remote Operation 3 1 Index of Common Commands 3 2 Alphabetic List of Commands 33 Introduction o 34 Comm Sn Gr ke BELA la dia 3 5 Status Model 4 Performance Tests 41 Getting Ready eue ies E MESE a dus 4 2 Performance Tests 0 00004 43 Calibration 00 00004 5 Circuitry 5 1 Circuit Descriptions ss bea ee REX EG 52 Parts Lists eee 5 3 Schematic Diagrams 946 564 Vang vete te Ves ii Contents ASRS SIM960 Analog PID Controller General Information Safety and Precautions for Use A WARNING Service Because of the variety of uses for the SIM960 those responsible for the application and use of this control equipment must satisfy them selves that all necessary steps have been taken to assure that each application and use meets all performance and safety requirements including any applicable laws regulations codes and standards The SIM960 is not designed intended or sold for use in hazardous environments requiring fail safe operation including without lim itation operation of nuclear facilities aircraft or spacecraft control systems and life support or weapons systems The user must as
24. andard Event Status Register is true Master Summary Status Indicates whether one or more of the enabled status messages in the Status Byte register is true Communication Error Summary Bit Indicates whether one or more of the enabled flags in the Communication Error Status Register has become true 3 5 2 Service Request Enable SRE Each bit in the SRE corresponds one to one with a bit in the SB regis ter and acts as a bitwise AND of the SB flags to generate MSS ROS Bit 6 of the SRE is undefined setting it has no effect and reading it always returns 0 This register is set and queried with the SRE command This register is cleared at power on ASRS SIM960 Analog PID Controller 3 5 Status Model 3 5 3 Standard Event Status ESR The Standard Event Status register consists of 8 event flags These event flags are all sticky bits that are set by the corresponding event and cleared only by reading or with the CLS command Reading a single bit with the ESR i query clears only bit i Weight Bit Flag 1 0 OPC 2 1 INP 4 2 OYE 8 3 DDE 16 4 EXE 32 5 CME 64 6 URQ 128 7 PON OPC INP OYE DDE EXE CME URQ PON Operation Complete Set by the OPC command Input Buffer Error Indicates data has been discarded from the Input Buffer Query Error Indicates data in the Output Queue has been lost Device Dependent Error Undefined for SIM960 Execution Er
25. ault configuration The effect of this com mand is equivalent to the following sequence of commands e DISX ON e DISP PRP e SHFT OFF e GAIN 1 9 e APOL POS e INTG 1 0 e DERV 1 0E 6 e OFST 0 0 e RATE 1 0 e PCTL ON e ICTL OFF e DCTL OFF e OCTL OFF e RAMP OFF e SETP 0 0 must not precede RAMP OFF e MOUT 0 0 e ULIM 10 0 ASRS SIM960 Analog PID Controller 3 4 Commands Example LLIM 10 0 e INPT EXT e AMAN PID e TOKN OFF e SOUT The baud rate of the SIM960 is unaffected by RST The entire status model is also unaffected by RST RST CONS z Example Console Mode Set query the Console mode to Z OFF 0 ON 1 CONS causes each character received at the Input Buffer to be copied to the Output Queue At power on CONS is set to OFF CONS ON DN Example Identify Read the device identification string The identification string is formatted as Stanford Research_Systems SIM960 s n ver where SIM960 is the model number js the 6 digit serial num ber and is the firmware revision level IDN Stanford Research Systems SIM960 s n003173 ver2 15 TST Example Self Test There is no internal self test in the SIM960 so this query always returns 0 TST 0 SIM960 Analog PID Controller SRS Remote Operation Example Operation Complete Operation Complete Sets the OPC flag in the ESR register The query form
26. d setpoint An external setpoint can be supplied at the Setpoint BNC input When the internal setpoint is selected the BNC connector is disconnected from the SIM960 circuitry e The Output BNC connector can be toggled between PID Con trol mode and Manual mode using Output in the OUTPUT section of the front panel In manual mode the SIM960 output is set to the value indicated by the manual parameter The common mode range of the Measure and Setpoint inputs extends from 10 V to 10 V If either input is outside this range the overload LED indicator lights The differential input range is 1 V Whenever the difference between Setpoint and Measure exceeds this range the overload LED indica tor turns on When connected with overall negative feedback and reasonably well tuned the SIM960 keeps the difference between the setpoint and measure inputs as small as possible so the differential input range is unlikely to be exceeded Before the SIM960 has been tuned for a given system however this may not be true It is helpful to keep in mind that exceeding the 1 V differential input range will saturate the error amplifier even if the output signal would otherwise be within the upper and lower Limits setting In such situations the controller will be effectively limited at some intermediate value ASRS SIM960 Analog PID Controller 12 Front Panel Operation 1 2 2 Ramping 1 2 3 Connections The ramping feature of the SIM
27. ds time to build up a response To further enhance the response of the process to rapid changes deriva tive control is often employed Derivative control is proportional to the rate of change of the error so it is relatively unresponsive to slow changes but rapid changes to the system produce a significant response Derivative control reduces oscillations that can result from step changes to a system 1 During the tuning process it is important to keep in mind that the differential input range of the SIM960 is 1 0 V It is good practice to occasionally glance at the OVLD indicator to ensure the input amplifier is not saturated ASRS SIM960 Analog PID Controller 22 Ziegler Nichols Tuning 2 5 2 2 Ziegler Nichols Tuning For many applications a good starting point for tuning is one of the two classic Ziegler Nichols methods These two methods are briefly described below for more details see for example Astrom amp H gglund PID Controllers Theory Design and Tuning Instru ment Society of America 1995 2 2 1 Open loop tuning The open loop Ziegler Nichols method involves introducing a small step change to the process under control and making a few mea surements from the response The procedure is e Switch the SIM960 into Manual mode and then adjust until the process is stable and near the desired operating point e Now make a small sudden step change A in the control signal Call this time f 0
28. e 10 20 samples at a known time interval during a ramp based on the ramp rate being tested and the range of the ramp Then extract the ramp rate by calculating the average slope of the ramp data using a least squares fit routine For each ramp rate being tested measure both a positive going ramp and a negative one and calculate the average ramp rate magnitude SIM960 Analog PID Controller fs RS 4 6 Performance Tests Rate V sec 0 01 10000 In each case the ramp rate magnitude should be within 2 of the programmed value 4 2 7 Offset Control Accuracy e Ground both the Measure and Setpoint inputs of the SIM960 using either BNC grounding caps or 50 O terminators e Reset the SIM960 using RST e Turn off P control using PCTL OFF e Turn on Offset control using OCTL ON e Change the Offset value to 0 000 V 8 000 V and 8 000 V us ing the OFST command and observe the Output display at each level In each case the output display value should be within 5 mV of the programmed offset 4 2 8 Manual Output Accuracy e Reset the SIM960 using RST e Select Manual output using AMAN MAN e Use the MOUT command to change the manual output level to 0 000 V 8 000 V and 8 000 V and observe the Output display value for each level In each case the output display value should be within 5 mV of the programmed manual output value 4 3 Calibration If any of the preceeding tests fail the SIM960 s
29. e P until the process starts to oscillate e Record this value of P as K the ultimate gain Also observe the period of the oscillations Th From K and T Ziegler and Nichols again suggest tuning for P PI and PID control as shown in Table 2 2 Control P I D P K 2 PI 2K 5 5 4T PID 3K 5 2 T T 8 Table 2 2 Ziegler Nichols closed loop tuning parameters 4 SRS SIM960 Analog PID Controller 23 Anti Windup and Conditional Integration 257 2 3 Anti Windup and Conditional Integration For better integral performance the SIM960 features anti windup circuitry in the form of conditional integration The purpose of anti windup is to improve the controller s ability to recover from output saturation When the output saturates the error is likely to be large since the process is unable to provide power fast enough to recover the process output However the integrator contribution may not account for the full amount of the controller output in this case Subsequently the integrator continues to integrate the error until the integrator output saturates This winding up aspect of integral control becomes a problem when the process recovers and the error level passes through zero because the error must move significantly beyond zero for the integrator to unwind from saturation In general once the controller output is clamped at a limit nothing is accomplished by driving it harder into that
30. e deter mined by the current real time condition of the events defined in the instrument status register see Section 3 5 8 Reading the instrument condition register does not affect the register INCR 16 INSR i Example Instrument status register Query the instrument status register bit i INSR 16 INSE i Ul Example Instrument status enable register Set query the instrument status enable register bit i to j INSE 16 ADSR i Example A to D status register Query the analog to digital status register bit i When new data become available from the A to D converter the A to D status register bit corresponding to the channel of the new data is set see Section 3 5 10 ADSR 15 ADSE i U Example A to D status enable register Set query the A toD status enable register bit i to j ADSE 2 SIM960 Analog PID Controller fs RS Remote Operation Example Pulse STATUS Mode Set query the Pulse STATUS Mode to Z OFF 0 ON 1 When PSTA ON is set any new service request will only pulse the STATUS signal low for a minimum of 1 us The default behavior is to latch STATUS low until a STB query is received At power on PSTA is set to OFF PSTA OFF 3 4 9 Interface commands The Interface commands provide control over the interface between the SIM960 and the host computer RST Reset Reset the SIM960 to its def
31. e usage examples vary with respect to set query optional param eters and token formats These examples are not exhaustive but are intended to provide a convenient starting point for user program ming SIM960 Analog PID Controller fs RS 3 10 Remote Operation 3 4 3 Controller settings commands PCTL z Proportional action ON OFF Set query the proportional control to Z OFF 0 ON 1 When ON the PID Control path includes the proportional control term Example PCTL 1 ICTL z Integral action ON OFF Set query the integral control to Z OFF 0 ON 1 When ON the PID Control path includes the integral control term Example ICTL 0 DCTL z Derivative action ON OFF Set query the derivative control to Z OFF 0 ON 1 When ON the PID Control path includes the derivative control term Example DCTL OFF OCTL z Offset ON OFF Set query the offset control to Z OFF 0 ON 1 When ON the PID Control path includes the constant output offset Example OCTL ON GAIN f Proportional Gain Set query the proportional gain P to f in V V Values may be entered in decimal or exponential format and are signed GAIN may be set with 2 digits of resolution for 1 0 lt P lt 10 and with single digit resolution for 0 1 lt P lt 0 9 Note that setting GAIN does not modify whether the proportional term is enabled or disabled For on off control see PCTL Setting GAIN overrides the previ
32. ed at its limit 1 2 5 Restoring the default configuration The default configuration of the SIM960 can be restored in either of two ways From the front panel or via the remote interface To restore from the front panel first turn off the power to the SIM960 by switching its SIM900 Mainframe to Standby then switch the ASRS SIM960 Analog PID Controller 13 Rear Panel Monitoring 1 7 power on while holding down Ramp Start Stop Keep the button depressed for about one second after power comes on The default configuration can also be restored via the remote interface using the RST command 1 3 Rear Panel Monitoring Two analog monitor signals are available at the rear panel of the SIM960 see Figure 1 2 Figure 1 2 The SIM960 rear panel 1 3 1 Error Monitor The upper BNC connector carries a buffered copy of the P x e output of the error amplifier This output is always available even when the P term is disabled from the control law It is also active when the main SIM960 output is set to Manual mode 1 3 2 Input Setpoint Monitor The lower BNC is a copy of the internally generated setpoint voltage This output is also always available even when the Setpoint mode is set to External SIM960 Analog PID Controller SRS 1 8 Getting Started 1 4 SIM Interface N CAUTION 1 4 1 The primary connection to the SIM960 Analog PID Controller is the rear panel DB 15 SIM interface connector Ty
33. erial data byte is lost due to internal processor latency Causes the Input Buffer to be flushed and resets the command parser OVR Input Buffer Overrun Set when the Input Buffer is overrun by incoming data Causes the Input Buffer to be flushed and resets the command parser RISH Undefined for the SIM960 Command Error Indicates a parser detected error CTSH Undefined for the SIM960 DCAS Device Clear Indicates the SIM960 received the Device Clear signal an RS 232 break Clears the Input Buffer and Output Queue and resets the command parser 3 5 6 Communication Error Status Enable CESE The CESE acts as a bitwise AND with the CESR register to produce the single bit CESB message in the Status Byte Register SB It can be set and queried with the CESE command This register is cleared at power on 3 5 7 Instrument Status INCR The Instrument Condition Register consists of 5 single bit monitors of condition events within the SIM960 Bits in the INCR reflect the real time values of their corresponding signals Reading the entire register or individual bits within it does not affect the value of INCR SRS SIM960 Analog PID Controller 3 5 Status Model 3 29 Weight Bit Flag 1 0 OVLD 2 1 ULIMIT 4 2 LLIMIT 8 3 ANTIWIND 16 4 RSTOP 32 5 undef 0 64 6 undef 0 128 7 undef 0 OVLD Amplifier Overload Set to indicate an overload either differ ential or common mode
34. esolution Note that set ting OFST does not modify whether the offset is enabled or disabled For on off control see OCTL The allowed range is 10 000 lt OFST 10 000 OFST 12 3E 2 OFST 0 123 SIM960 Analog PID Controller fs RS 3 12 Remote Operation 3 4 4 Controller configuration commands AMAN z Output Manual Output PID Control Set query controller output state to Z MAN 0 PID 1 Example AMAN 1 INPT z Input Internal External Setpoint Set query setpoint input state to Z INT 0 EXT 1 Example INPT INT SETP f New setpoint Set query the setpoint value to f in volts The setpoint can be set with millivolt resolution If ramping is en abled see RAMP SETP will initiate a ramp to f Otherwise the setpoint value changes immediately to the new value The allowed range is 10 000 lt SETP lt 10 000 Example SETP 1 234 RAMP z Internal setpoint ramping ON OFF Set query internal setpoint ramping to Z OFF 0 ON 1 When ON the changes to the internal setpoint are made with constant slew rate ramping enabled Example RAMP 1 RATE f Setpoint ramping Rate Set query the setpoint rate to f in V s RATE may be set with 2 digits of resolution for values above 10 and with signle digit resolution below that Note that setting RATE does not modify whether setpoint changes are made with constant slew rate ramping or not For on off control of linear rampin
35. g 10 10 V resolution 1 mV Ramp Rate 107 10 V s Noise f gt 100 Hz 20 nV VHz RTI Temperature 14 0 40 C Power 15 5 V DC Supply current 150 15 V 80 5V mA Number of inputs 2 Interface Serial RS 232 through SIM interface Connectors BNC 3 front 2 rear DB 15 male SIM interface Weight 2 1 lbs Dimensions 3 0 W x 3 6 H x 7 0 D ASRS SIM960 Analog PID Controller 1 Getting Started In This Chapter This chapter gives you the necessary information to get started quickly with your SIM960 Analog PID Controller 1 1 1 2 1 3 1 4 Generala coartada as Front Panel Operation ed OPUS La RE EE ir 1 22 Ramping ornice A 12 3 Connectons aso ex 124 Bar displ ys s s duco Seite Seeds 12 5 Restoring the default configuration Rear Panel Monitoring 1121 11 1 3 1 Error Monitor 121 1 3 2 Input Setpoint Monitor SIM Interface sugar skrek ee x de 1 4 1 SIM interface connector 1 4 2 Direct interfacing 1 2 Getting Started 1 1 General The SIM960 is designed to maintain stability in systems requiring low noise and wide bandwidth The controller design consists of a front end differential input amplifier followed by an integrator and a differentiator arranged in what is known as the ideal PID topology The input amplifier the er
36. g see RAMP The allowed range is 10 lt RATE x 10 Example RATE 2 2E 3 RATE 0 2E 2 ASRS SIM960 Analog PID Controller 3 4 Commands RMPS Example Setpoint ramping status Query the ramp status For slow ramps of the internal setpoint the RMPS query will mon itor the real time status of a setpoint transition The response is one of the following token values IDLE 0 PENDING 1 RAMPING 2 PAUSED 3 RMPS RAMPING STRT z Example Pause or continue ramping Cause a setpoint ramping event in progress to pause STOP or con tinue START z STOP 0 START 1 Note that STRT cannot be used to initiate a new setpoint transition from the RMPS PENDING state this can only be accomplished by pressing Ramp Start Stop on the front panel STRT START MOUT f Example Manual Output Set query the manual output value to f in volts The manual output can be set with millivolt resolution Note that setting MOUT does not modify whether the controller is in manual or PID control mode For on off control of manual output see AMAN The allowed range for MOUT is 10 000 lt MOUT lt 10 000 MOUT 8 000 ULIM f Upper Output Limit Set query the upper output limit to f in volts The upper limit can be set with 10mV resolution Note that re gardless of the operating mode of the SIM960 see AMAN the out put voltage will always be clamped to remain less p
37. gain accuracy tests but now add the divider network to form a closed loop configuration e Connect the top of the divider to the Output of the SIM960 connect the center of the divider to the Measure input of the SIM960 and connect the bottom of the divider to ground This ground should be accessed at one of the BNC shields e Reset the SIM960 via the remote interface using RST e Set the P gain parameter to 8 0 using GAIN 8 0 e Turn off the P gain control using PCTL OFF e Turn on the I control using ICTL ON e With the SR785 in swept sine mode and the source output amplitude at 0 5 V measure the frequency response at the fre quencies below for each I setting I 1 sec frequency expected response 5 10Hz 0 6366 100 150 Hz 0 8488 2x10 3 0kHz 0 8488 5x10 100 kHz 0 6366 5x10 100 kHz 6 366 In each case the frequency response should be within 2 of the programmed gain value 4 2 6 Ramp Rate Accuracy To test the ramp rate wire the SIM960 as a follower by connecting the output to the Measure input Reset the SIM960 using RST Set the P gain to 8 0 using GAIN 8 0 and turn off the P control using PCTL OFF Turn on I control using ICTL ON and set the I parameter to 10 using INTG 1 0E5 The Setpoint input should be set to Internal using INPT INT and ramping should be enabled using RAMP ON The Multimeter can be used to measure the SIM960 output during a ramp Set up the multimeter to tak
38. h descriptor shows which parameter is displayed When Shift is highlighted pressing Select steps the parameter selection backwards ASRS SIM960 Analog PID Controller 12 Front Panel Operation 5IM960 Analog PID Controller Pxe Out mo MUL B Manual Wi Limits m Setpoint m Offset a B Measure w SP Ramp a mPxe Internal Setpoint W Output Setpoint Measure 5 del off Output Px fe Ifedt DE set u a INPUTS E z OUTPUT Measure ovLD Setpoint m Internal m Manual m External W PID Control N Figure 1 1 The SIM960 front panel The P I D Offset and SP Ramp parameters may be en abled disabled with On Off Each of these parameters has an additional indicator to the right of the descriptor to indicate the on off status The Limits parameter has two sublevels upper and lower limit The Setpoint Measure P x e and Output values are display only All the other values can be changed using the AV but tons the digit selected for adjustment is indicated by its flash ing brightness Change the digit selection while Shift is high There are two formats for the numeric display Exponential and fixed decimal The format used for a particular param eter depends on its range Parameters P I D and SP Ramp rate vary by several orders of magnitude and are therefore displayed in exponential format while all other parameters range from 10 V to 10
39. hould be returned to the factory for recalibration Contact Stanford Research Systems or an authorized representative before returning the SIM960 4 SRS SIM960 Analog PID Controller 5 Parts Lists and Schematics This chapter presents a brief description of the SIM960 circuit design A complete parts list and circuit schematics are included In This Chapter 5l Circuit Descriptions sus ss Aa 5 2 5 11 Microcontroller 5 2 5 1 2 Front Panel Display 5 2 5 13 Input Amplifier 5 2 5 14 Proportional Integral Derivative 5 3 5 1 5 Output Circuitry ue pacta xe RES 5 3 52 Parts Lists wa w vos i Kec e TWE ea 5 4 5 21 Digital Board amp Front Panel 5 5 5 2 2 Analog BOSE A eee E PA ok 5 6 5 3 Schematic Diagrams 5 7 5 2 Circuitry 5 1 Circuit Descriptions 5 1 1 Microcontroller 5 1 2 Front Panel Display 5 1 3 Input Amplifier The SIM960 consists of three separate printed circuit boards the digital board the front panel board and the analog board The digital board is directly beneath the left hand cover as viewed from the front of the module Pages 1 3 of the schematics correspond to the digital board Page 4 is the front panel board and pages 5 9 are the analog board The SIM960 is controlled by microcontroller U103 It is clocked at 10 MHz by the oscillator built around U102 which will track the reference REF_10M
40. im iters Since there are four monitor channels that can be streamed to output and any combination of the four may be streamed the comma delimiters allow unambiguous identification of channel data The record format is SMON MMON EMON OMON Example RFMT ON SMON 3 MMON 3 EMON 3 OMON 3 00 099909 00 006053 00 105601 01 106135 00 099909 00 006031 00 105615 01 106123 00 099915 00 006001 00 105636 01 106151 SIM960 Analog PID Controller fs RS Remote Operation SOUT z Example Stop Streaming Turn off streaming of channel z SMN 0 MMN 1 EMN 2 OMN 3 If the optional parameter Z is not specified then all streaming outputs are turned off SOUT FPLC i Frequency of Power Line Cycle Set query the power line cycle frequency to i 50 60 Hz FPLC is used to program the power line rejection frequency for the precision voltage monitors SMON MMON EMON OMON Example FPLC 60 3 4 6 Display commands DISP z Select Field Example Set query the field level to be displayed to zj Allowed values of z are PRP Proportional gain IGL 1 Integral gain DER 2 Derivative gain OFS 3 Output offset RTE 4 Setpoint rate STP 5 Setpoint value MNL 6 Manual output value ULM 7 Upper limit of output LLM 8 Lower limit of output SMN 9 ADC measurement of Setpoint input MMN 10 ADC measurement of Measure input EMN 11 ADC measurement of P Amplified error OMN
41. in swept sine mode measure the frequency response at 1 KHz adjusting SIM960 Analog PID Controller ASRS Performance Tests the source output amplitude for each P gain setting from the table below P gain Source amplitude volts 1000 0 005 In each case the frequency response should be within 1 of the programmed gain value The gain should not vary by more than 1 over the full 100 kHz bandwidth at the P gain 8 setting 4 2 4 Derivative Gain Accuracy Use the same connections as for the proportional gain accuracy test Reset the SIM960 via the remote interface using RST Turn off the P gain control using PCTL OFF Turn on the D control using DCTL ON With the SR785 in swept sine mode and the source output amplitude at 0 5 V measure the frequency response at the frequencies below for each D setting D sec frequency expected response 1 00 x 103 1 600 kHz 0 10053 1 01 x 107 1 600kHz 0 10154 1 00 x 1074 1 600 kHz 1 0053 1 01 x 10 1 600 kHz 1 0154 1 00x10 160Hz 1 0053 1 01x10 3 160Hz 1 0154 1 00 x 10 16Hz 1 0053 1 01 x 107 16Hz 1 0154 1 00 x 107 1 6Hz 1 0053 1 01 x 107 1 6Hz 1 0154 In each case the frequency response should be within 2 of the programmed gain value ASRS SIM960 Analog PID Controller 42 Performance Tests 4 5 4 2 5 Integral Gain Accuracy Use the same connections as for the proportional and derivative
42. istor R615 in order to roughly match the switch resistance of each of the switches in U601 5 1 5 Output Circuitry U807 is used to switch the ouput of the SIM960 between Manual and PID modes The signal then passes through two cascaded diode limiter circuits D801 and D802 clamp the output signal with respect to the upper limit voltage generated by U508A together with U509B and U509C The effect of cascading two diode limiter circuits is to narrow the clamping range by roughly a factor of two down to about 100 mV Comparator U805 switches high when the output signal going into the limiter circuit at R823 exceeds the upper limit voltage The in verting input of U805 is referenced to the upper limit voltage through the divider combination R844 and R845 effectively shifting the sat uration turn on location with respect to the clamping knee The lower limit clamp is similarly implemented by D803 and D804 The output of the limiter circuit is buffered by a composite amplifier consisting of U821 and U822 This arrangement provides the driving capability of the LT1010 without suffering its large input offset volt age since the output of U822 is servoed to the noninverting input to SIM960 Analog PID Controller fs RS Circuitry 5 2 Parts Lists U821 via the feedback resistor R819 U823 is a photo MOS switch that remains off during power up until the 15 V rails reach about 13 V By then the output of the Manual DAC which i
43. larity should be used Care should be taken in designing the process The sensor should be situated so that it is responsive to changes to the part of the system under control Placing the sensor too remotely can result in a time delay which limits the quality of control Also the sensor should primarily measure the system s response to external changes rather than measure the changes directly The latter can sometimes be used to help the controller anticipate transients but at the risk of sacrificing accuracy in reaching the target setpoint Tuning a PID controller amounts to determining what the relative contributions should be from each of the three types of control The simplest approach is to start with proportional control and add inte SIM960 Analog PID Controller fs RS Advanced Topics gral and derivative one at a time A simple P controller generates a control variable that is proportional to the error signal Increasing the P gain should cause the process output to respond by moving closer to the setpoint Generally enough amplification should be used so that the process output is brought reasonably close to the setpoint Too much gain however will cause the system to oscillate Start with a small P gain and increase by factors of two until the system begins to oscillate Then back off in small amounts until stability is recovered While it is possible to maintain stability with a simple P controller in general thi
44. limit by more integration In fact it only makes it harder to recover from saturation since the result is usually large swings back and forth from limit to limit There are a variety of anti windup strategies to mitigate this effect A simple way to implement anti windup is to switch off the integrator whenever the output saturates This is not the same as resetting the integrator zeroing its output by discharging the feedback capaci tance because the output simply stops moving but does not go to zero It is equivalent to momentarily zeroing the integrator input so that there is no signal to integrate while the output is saturated An improvement to this scheme comes from recognizing that not all saturation conditions cause unwanted integrator wind up For example suppose the controller process history were such as to pro duce the following conditions e Error signal negative e Integrator output finite not saturated e Controller output saturated at the positive limit Then the integrator output would be moving in the negative direc tion since its input the error is negative This would not cause the controller output to be pushed harder into saturation in fact it may eventually pull it out of saturation So stopping the integrator would hinder the controller s effort to recover the process variable The SIM960 uses a technique called conditional integration Con ditional integration only stops the integrator when the pola
45. meter that causes streaming of Measure data If i is specified then i measurements will be output at a rate of approximately half a second per measurement If i is specified as 0 then measurements will be output indefinitely The SOUT command can be used to stop streaming Example MMON 00 005900 ASRS SIM960 Analog PID Controller 3 4 Commands 3 15 EMON i Amplified Error Monitor Query the P x e voltage in volts i is an optional parameter that causes streaming of P x e data If i is specified then measurements will be output at a rate of approx imately half a second per measurement If i is specified as 0 then measurements will be output indefinitely The SOUT command can be used to stop streaming Example EMON 00 105537 OMON i Output Monitor Query the Output voltage in volts OMON always reports the voltage generated at the front panel OUT PUT BNC connector regardless of the state of AMAN i is an optional parameter that causes streaming of Output data If i is specified then i measurements will be output at a rate of approximately half a second per measurement If i is specified as 0 then measurements will be output indefinitely The SOUT command can be used to stop streaming Example OMON 01 106139 RFMT z Output Streaming Records Format Set query the output streaming record format to Z OFF 0 ON 1 When ON data are output on a single line with three comma del
46. n The controller uses the amplified error P x e to generate three control signals 1 Proportional the P amplified error with no changes 2 Integral the time integral of the amplified error signal multi plied by a gain coefficient I 3 Derivative the time derivative of the amplified error signal multiplied by a gain coefficient D These signals as well as an Offset are combined at a summing junction to produce the controller output see Eqn 1 2 Figure 2 1 shows a schematic representation of the SIM960 controller topology Note the proportional gain coefficient is common to all three terms so the net integral and derivative gains are P x I and P x D respectively whether or not proportional control is enabled The controller monitors the process output and makes small adjust ments to the process in order to minimize deviations of Measure from Setpoint due to external disturbances To accomplish this the controller must be properly tuned meaning that the gains for each of the three control signals proportional integral and derivative must be chosen appropriately to match the behavior of the process A well tuned controller should be able to maintain a stable process output The control loop feedback should be negative However because the polarity of the process response to the controller output is an arbitrary function of the design of the system it is vital that the controller polarity be chosen properly Based on
47. n it are cleared These are sometimes known as sticky bits since once set a bit can only be cleared by reading its value Event register names end with SR These read write registers define a bitwise mask for their cor responding event register If any bit position is set in an event register while the same bit position is also set in the enable register then the corresponding summary bit message is set Enable register names end with SE SIM960 Analog PID Controller ASRS 3 26 Remote Operation 3 5 1 Status Byte SB The Status Byte is the top level summary of the SIM960 status model When masked by the Service Request Enable register a bit set in the Status Byte causes the STATUS signal to be asserted on the rear panel SIM interface connector Weight Bit Flag 1 0 INSB 2 1 ADSB 4 2 undef 0 8 3 undef 0 16 4 IDLE 32 5 ESB 64 6 MSS 128 7 CESB INSB ADSB IDLE ESB MSS CESB InstrumentStatus Summary Bit Indicates whether one or more of the enabled flags in the Instrument Status Register has be come true Analog to Digital Status Bit Indicates whether one or more of the enabled flags in the Analog to Digital Status Register has become true Indicates that the Input Buffer is empty and the command parser is idle Can be used to help synchronize SIM960 query responses Event Status Bit Indicates whether one or more of the enabled events in the St
48. nternal External Setpoint SETP f 3 12 New setpoint RAMP z 3 12 Internal setpoint ramping ON OFF RATE f 3 12 Setpoint ramping Rate RMPS 3 13 Setpoint ramping status STRT z 3 13 Pause or continue ramping MOUT f 3 13 Manual Output ULIM f 3 13 Upper Output Limit LLIM f 3 14 Lower Output Limit Monitor SMON i 3 14 Setpoint Input Monitor MMON i 3 14 Measure Input Monitor EMON i 3 15 Amplified Error Monitor OMON i 3 15 Output Monitor RFMT z 3 15 Output Streaming Records Format SOUT 2 3 16 Stop Streaming FPLC i 3 16 Frequency of Power Line Cycle ASRS SIM960 Analog PID Controller 3 1 Index of Common Commands 3 3 Display DISP z 3 16 Select Field SHFT 2 3 16 Shift Status DISX z 3 17 Front Panel Display Enable Serial Communications BAUD i 3 17 Baud Rate FLOW z 3 17 Flow Control PARI z 3 17 Parity Status CLS 3 17 Clear Status STB i 3 18 Status Byte SRE i tj 3 18 Service Request Enable ESR i 3 18 Standard Event Status ESE i i 3 18 Standard Event Status Enable CESR i 3 18 Comm Error Status CESE i j 3 19 Comm Error Status Enable INCR i 3 19 Instrument condition register INSR i 3 19 Instrument status register INSE i 3 19 Instrument status enable register ADSR i 3 19 A to D status register ADSE i j 3 19 A to D status enable register PSTA z 3 20 Pulse STAT
49. on sider an input sine wave of frequency 1 Hz Since frequency is low compared to the inverse of the decay time the maximum and min imum peak values are indistinguishable and the signal appears as a single LED that tracks the sine wave As the frequency increases the maximum peak does not decay quickly enough to track the neg ative excursions the signal and the minimum peak also fails to track positive excursions So there appear to be two lighted LEDs slightly separated roughly tracking the sine wave As the frequency is fur ther increased to well above the decay time inverse the two lighted LEDs no longer decay at all from their peak levels so there appear to be two lighted LEDs marking the maximum and minimum peaks of the sine wave Thus a slowly varying signal appears as a single lighted LED in the display tracking the signal changes with time But a quickly varying signal however appears as two lighted LEDs marking the maximum and minimum excursions of the signal in time The range of the P x e bar display is 10 V The Output bar display has a range determined by the user programmed upper and lower limits For example if the limits were set to 5 V and 1 V the full range of the bar display would be 6 V and 0V would no longer correspond to the center of the bar display but would be eth of the way up from the bottom Also the Output bar display has a red LED on each end to indicate whether the controller output is saturat
50. ositive than the ULIM limit Combined with the LLIM limit this results in the output obeying 10 00 lt LLIM lt Output lt ULIM lt 10 00 The allowed range is LLIM lt ULIM lt 10 00 SIM960 Analog PID Controller fs RS Remote Operation 3 4 5 Monitor commands Lower Output Limit Set query the lower output limit to f in volts The lower limit can be set with 10 mV resolution The output voltage of the SIM960 will always be clamped to remain less negative than the LLIM limit See ULIM for more details The allowed range is 10 00 x LLIM lt ULIM SMON i Setpoint Input Monitor Query the Setpoint input voltage to the error amplifier in volts If INPT INT is set then SMON monitors the value of the internally generated setpoint If INPT EXT then SMON monitors the voltage applied at the front panel Setpoint BNC input i is an optional parameter that causes streaming of Setpoint data If i is specified then i measurements will be output at a rate of approximately two measurements per second If i is specified as 0 then measurements will be output indefinitely The SOUT command can be used to stop streaming Example SETP 1 2 SMON 5 01 004496 01 066567 01 128909 01 191273 01 200073 MMON i Measure Input Monitor Query the Measure input voltage to the error amplifier in volts MMON always reports the voltage applied at the front panel Mea sure BNC input i is an optional para
51. ous setting of APOL The allowed range for GAIN is 107 lt P lt 10 Example GAIN 2 5E 2 ASRS SIM960 Analog PID Controller 3 4 Commands APOL z Example Controller Polarity Set query the proportional gain polarity to z POS 1 NEG 0 Set ting APOL will override the sign of a previously commanded GAIN APOL POS INTG f Example Integral Gain Set query the integral gain I to f in V V s INTG may be set with 2 digits of resolution for 10 lt I lt 5 x 10 and with single digit resolution for 10 lt I lt 9 x 107 Integral gains are unsigned positive values only Note that setting INTG does not modify whether the integrator is enabled or disabled For on off control see ICTL The allowed range for INTG is 1072 lt 1 lt 5 x10 INTG 1 5E 3 DERV f Example Derivative Gain Set query the derivative gain to f in V V s DERV may be set with 2 digits of resolution for 10 lt D lt 10 and with single digit resolution for 107 lt I lt 9 x 10 5 Derivative gains are unsigned positive values only Note that setting DERV does not modify whether the derivative is enabled or disabled For on off control see DCTL The allowed range for DERV is 1076 lt D lt 10 DERV 0 000015 DERV 1 5E 5 OFST f Example Output Offset Set query the output offset to f in volts The offset voltage can be set with millivolt r
52. pically the SIM960 is mated to a SIM900 Mainframe via this connection either through one of the internal mainframe slots or the remote cable interface It is also possible to operate the SIM960 directly without using the SIM900 Mainframe This section provides details on the interface The SIM960 has no internal protection against reverse polarity missing supply or overvoltage on the power supply pins Misapplication of power may cause circuit damage SRS recommends using the SIM960 together with the SIM900 Mainframe for most applications SIM interface connector The DB 15 SIM interface connector carries all the power and commu nications lines to the instrument The connector signals are specified in Table 1 1 Direction Pin Signal Src 2 Dest Description 1 SIGNAL GND MF SIM Ground reference for signal 2 STATUS SIM gt MF Status service request GND asserted 5 V idle 3 RTS MF gt SIM HW Handshake 5 V talk GND stop 4 CIS SIM gt MF HW Handshake 5 V talk GND stop 5 REF 10MHZ MF gt SIM 10 MHz reference optional connection 6 5V MF gt SIM Power supply no connection in SIM960 7 15V MF gt SIM Power supply analog circuitry 8 PS_RTN MF gt SIM Power supply return 9 CHASSIS GND Chassis ground 10 TXD MF gt SIM Async data start bit 0 5 V 1 GND 11 RXD SIM gt MF Async data start bit 0 5 V 1 GND 12 REF 10MHz M
53. r equipment is possible Typesetting conventions used in this manual are e Front panel buttons are set as Button Adjust 11 is shorthand for Adjust i amp Adjust 1 e Front panel indicators are set as Overload e Remote command names are set as IDN e Literal text other than command names is set as OFF Remote command examples will all be set in monospaced font In these examples data sent by the host computer to the SIM960 are set as straight teletype font while responses received by the host computer from the SIM960 are set as slanted teletype font SIM960 Analog PID Controller fs RS vi General Information Specifications Performance Characteristics Amplifier Settings Amplifier Performance Configuration Inputs Setpoint Generator Operating General Characteristics Min Typ Max Units Control type Analog PID Offset Input Range 10 10 V common mode 1 1 V differential Proportional gain 1071 10 V V Integral gain 107 5x10 1 s eff time const 2 x 1079 10 S Derivative gain 10 5 10 Offset 10 10 V resolution 1 mV Bandwidth 100 kHz Propagation delay 1 us Noise f gt 20Hz 8 nV NHz RTI Output Range 10 10 V Parameter control Digital Parameter accuracy 1 Stability 200 ppm C Display Resolution 4 digits Measure BNC 1 MQ 10 V range Ext Setpoint BNC 1 MO 10 V range Settin
54. rity of the error is such as to drive the integrator toward the saturated limit SIM960 Analog PID Controller fs RS 2 8 Advanced Topics 2 4 Bumpless Transfer 2 4 4 Manual to PID 2 4 2 PID to Manual When switching the output mode between Manual and PID Con trol transients on the output signal can disturb the system under control Minimizing these switching transients is known as bump less transfer The SIM960 supports bumpless transfer under certain conditions as described below When switching from Manual output to PID Control output bump less transfer is only possible if the integral term is enabled When I is turned on and the SIM960 is in Manual output mode the input to the integrator is rerouted to integrate the difference between Manual and the deselected PID Control output This effectively allows the PID Control to track the Manual value presetting the integrator as necessary Then when the output is switched back to PID Control the controller output is already the same as the Manual output level Were this not the case the integrator output would likely saturate while in manual mode and upon switching to PID Control mode the controller output would suddenly jump Bumpless transfer insures that the transition from Manual to PID Control mode is smooth An additional feature of the SIM960 is the ability to preset the manual level to the current PID control output level so that switching from PID mode
55. rms of most commands are supported allowing the user complete control of the amplifier from a remote computer either through the SIM mainframe or directly via RS 232 see section 1 4 2 1 See Table 1 1 for the specification of the DB 15 SIM Interface Con nector 3 3 1 Power on configuration 3 3 2 Buffers 3 3 3 Device Clear The settings for the remote interface are 9600 baud with no parity and hardware flow control and local echo disabled CONS OFF Most of the SIM960 instrument settings are stored in non volatile memory and at power on the instrument returns to the state it was last in when power was removed Exceptions are noted in the com mand descriptions Reset values of parameters are shown in boldface The SIM960 stores incoming bytes from the host interface in a 32 byte Input Buffer Characters accumulate in the Input Buffer until a command terminator either CR or LF is received at which point the message is parsed and executed Query responses from the SIM960 are buffered in a 32 byte Output Queue If the Input Buffer overflows then all data in both the Input Buffer and the Output Queue are discarded and an error is recorded in the CESR and ESR status registers The SIM960 host interface can be asynchronously reset to its power on configuration by sending an RS 232 style break signal From the SIM900 Mainframe this is accomplished with the SRST command if directly interfacing via RS 232 then use a
56. ror Indicates an error in a command that was successfully parsed Out of range parameters are an example The error code can be queried with LEXE Command Error Indicates a parser detected error The error code can be queried with LCME User Request Indicates a front panel button was pressed Power On Indicates that an off to on transition has occurred 3 5 4 Standard Event Status Enable ESE The ESE acts as a bitwise AND with the ESR register to produce the single bit ESB message in the Status Byte Register SB It can be set and queried with the ESE command This register is cleared at power on 3 5 5 Communication Error Status CESR The Communication Error Status register consists of 8 event flags each of which is set by the corresponding event and cleared only by reading or with the CLS command Reading a single bit with the CESR i query clears only bit i SIM960 Analog PID Controller fs RS 3 28 Remote Operation Weight Bit Flag 1 0 PARITY 2 1 FRAME 4 2 NOISE 8 3 HWOVRN 16 4 OVR 32 5 RTSH 64 6 CTSH 128 7 DCAS PARITY Parity Error Set by serial parity mismatch on incoming data byte FRAME Framing Error Set when an incoming serial data byte is missing the STOP bit NOISE Noise Error Set when an incoming serial data byte does not present a steady logic level during each asynchronous bit period window HWOVRN Hardware Overrun Set when an incoming s
57. ror amplifier differences the the two single ended inputs Setpoint and Measure and multiplies the resulting error signal e by the proportional gain The amplified error is then passed to three parallel control paths 1 The proportional path no change is made to the signal 2 The integral path with gain I 3 The derivative path gain D These three signals can be independently selected to combine at a summing amplifier which is then buffered to the output A constant offset can also be added which can be useful in applications that do not use the I term Mathematically the behavior is Setpoint Measure 1 1 Output P x eer feats DEE Offset 1 2 where the three terms within the braces and Offset can be indepen dently enabled or zeroed For internal stability the actual differentiator is rolled off to limit the derivative gain to 40 dB The output circuitry includes a soft limiter that turns on when the output exceeds user specified upper and lower limits and clamps the output to the limit level The output bar display on the right side of the front panel has red LEDs at each end to indicate when the output is being limited 1 2 Front Panel Operation This section discusses the essentials of operating the SIM960 locally from the front panel See Chapter 3 for remote operation e Press Select to choose which configuration parameter to view in the numerical display The indicator to the left of eac
58. s driving the SIM960 output during power up will have settled to near ground level and may be passed on to the output connector BNC without large start up transients Until switch U823 closes the SIM960 output is referenced to ground via R863 100k U820A provides a buffered analog output of the P x e signal at the back panel of the SIM960 Also the output of U731A is passed to the back panel to provide an analog output of the internally generated setpoint signal The parts list for the analog board is separate from the digital amp front panel boards ASRS SIM960 Analog PID Controller 5 2 Parts Lists 5 5 5 2 1 Digital Board 8 Front Panel Part Reference SRS P N Value Part Reference SRS P N Value C102 5 00366 100 18P R220 R221 R222 R223 R224 4 01136 110 1 58K C104 5 00376 100 120P R225 R226 R227 C105 5 00368 100 27P R228 4 01244 110 21 0K C107 C108 C110 5 00102 030 4 7U R232 4 01117 110 1 00K C116 C117 C118 C216 C220 5 00387 100 1000P R234 R236 R238 R240 R275 4 01146 110 2 00K C119 5 00345 090 4 0 34P R243 R248 R259 4 01184 110 4 99K C201 C202 C203 C204 5 00466 120 1U R249 R250 R254 R255 4 01243 110 20 5K C301 C221 5 00318 110 2 2U T35 R251 R260 R270 R271 R272 4 01242 110 20 0K C222 5 00522 110 47U T R273 C227 C228 5 00375 100 100P R257 4 01211 110 9 53K C241 C233 5 00367 100 22P R262 R263 4 00925 110 10 C240 5 00454 120 01U R274 4 01670 121 20K 1 2PPM D101 D102 D464 D465 D466 3 00945 143 BAT54S R280 R277 4 01280 110
59. s will lead to a finite non zero e Increasing P will tend to reduce the resulting e but too much proportional gain will eventually lead to oscillations One way to eliminate this nonzero error problem is to include an offset at the controller output The SIM960 Offset parameter can be turned on and adjusted to hold the process power at a level that main tains a smaller error However this is only a coarse improvement since the necessary power level may change with time Integral control provides an automatic way to dynamically adjust the effective offset to zero the error in older controllers integral action was called automatic reset for this reason Integral control simply integrates the error signal with respect to time Thus the controller output changes until the error has been reduced to zero near which point the controller output slows and stops changing If the error drifts over time the integrator responds by adjusting the controller output to cancel the error So it is much like having a dynamic output offset constantly responding to system changes As with proportional gain too much integral gain can cause oscillation Again start with a small I gain and increase by factors of two until oscillation begins then back off until stability is recovered Though integral control is effective at reducing the error it is not as effective as proportional control at responding quickly to changes This is because the integrator nee
60. semi colons so long as the Input Buffer does not overflow Commands are terminated by either CR or LF characters Null commands and whitespace are ignored Execution of the command does not begin until the command terminator is received Token parameters generically shown as Z in the command de scriptions can be specified either as a keyword or integer value Command descriptions list the valid keyword options with each keyword followed by its corresponding integer value For example to set the response termination sequence to CR LF the following two commands are equivalent TERM CRLF or TERM 3 For queries that return token values the return format keyword or integer is specified with the TOKN command The following table summarizes the notation used in the command descriptions ASRS SIM960 Analog PID Controller 3 4 Commands 3 9 symbol definition ij Integers fg Floating point values Z Literal token Required for queries illegal for set commands var Parameter always required var Required parameter for set commands illegal for queries var Optional parameter for both set and query forms 3 4 2 Examples Each command is provided with a simple example illustrating its usage In these examples all data sent by the host computer to the SIM960 are set as straight teletype font while responses received the host computer from the SIM960 are set as slanted teletype font Th
61. serial break signal After receiving the Device Clear the interface is reset to 9600 baud and CONS mode is turned OFF Note that this only resets the communi cation interface the basic function of the SIM960 is left unchanged to reset the meter see RST The Device Clear signal will also terminate any streaming outputs from the SIM960 due toan SMON MMON EMON and or OMON query of multiple conversions SIM960 Analog PID Controller fs RS 3 8 Remote Operation 3 4 Commands 3 4 1 Command syntax tokens This section provides syntax and operational descriptions for remote commands The four letter mnemonic shown in CAPS in each command se quence specifies the command The rest of the sequence consists of parameters Commands may take either set or query form depending on whether the character follows the mnemonic Set only commands are listed without the query only commands show the after the mnemonic and optionally query commands are marked with a Parameters shown in and are not always required Parameters in are required to set a value and should be omitted for queries Parameters in are optional in both set and query commands Parameters listed without any surrounding characters are always required Do not send or or as part of the command Multiple parameters are separated by commas Multiple commands may be sent on one command line by separating them with
62. st first is intended to optimize noise referred to input ASRS SIM960 Analog PID Controller 5 1 Circuit Descriptions 5 3 5 1 4 Proportional Integral Derivative The resulting amplified error signal P X e inverted at this point is then distributed to the three paths P I and D see schematic page 6 The P path is unchanged while the other two paths I and D each use 12 bit DACs U606A and U606B for vernier attenuation of the I and D gains Integral action is achieved using a multiplexed feedback capacitor design U602 is addressed to choose one of four capactors all of which are parallel to the fixed feedback capacitor C643 whose small capacitance sets the maximum integral gain value A similar switch ing method is employed in the derivative path to choose the input capacitance of the differentiating amplifier U609B Note R617 which limits the maximum derivative gain to just over 40 dB Each of the three signal paths P I and D passes through an analog switch U601A U601B and U601C respectively before being com bined at the summing junction the inverting input of op amp U605B These switches allow individual signals P I or D to be switched on or off at the summing junction Manual offset control also enters the summing junction though no switch is used since zeroing the off set circuit U610 with U611 is equivalent to switching out the offset signal Note that R643 is placed in series with the feedback res
63. sts This chapter describes the tests necessary to verify the SIM960 is operating correctly and within specified calibration In This Chapter TT Getting Ready 34223 9A Po Se 4 2 4 2 Performance Tests 4 2 421 Input Amplifier Offset 4 2 4 2 2 AtoDConvertertest 4 2 4 23 Proportional Gain Accuracy 4 3 4 2 4 Derivative Gain Accuracy 4 4 4 2 5 Integral Gain Accuracy 4 5 4 2 6 Ramp Rate Accuracy 4 5 4 2 7 Offset Control Accuracy 4 6 42 8 Manual Output Accuracy 4 6 43 Calibration oi a ee S 4 6 4 2 Performance Tests 4 1 Getting Ready 4 2 Performance Tests Recommended instruments include 1 SRS SIM900 Mainframe 2 Agilent 3458A 8 1 2 digit multimeter 3 SRS SR620 Time interval counter 4 SRS SR785 Dynamic signal analyzer 5 PC with remote interface to SIM900 Mainframe Also needed is a 96 1 resistive divider formed by soldering two re sistors a 210 0 O and a 20 00 kO resistor both 0 1 in series The resulting three conductors of this network will be labeled for future reference as follows The conductor running between the resistors will be called the center the conductor on the 210 O end will be the bottom and the conductor on the 20 kQ end will be the top This divider will be used externally to the SIM960 to test the integral gain accuracy The SIM960 should be given a
64. sure that any failure or misapplication of the SIM960 cannot lead to a con sequential failure of any interconnected equipment that could lead to loss of life or limb or property damage The illustrations charts and discussions shown in this manual are intended solely for purposes of example Since there are many vari ables and requirements associated with any particular control ap plication Stanford Research Systems does not assume responsibility or liability for actual use based upon the examples shown in this publication Do not install substitute parts or perform any unauthorized modifi cations to this instrument The SIM960 is a double wide module designed to be used inside the SIM900 Mainframe Do not turn on the power to the Mainframe or apply voltage inputs to the module until the module is completely inserted into the mainframe and locked in place Do not exceed 18 V at any input or output connector 111 iv General Information Symbols you may Find on SRS Products Alternating current Caution risk of electric shock Frame or chassis terminal Caution refer to accompanying documents Earth ground terminal 4 SRS SIM960 Analog PID Controller General Information Notation A WARNING N CAUTION The following notation will be used throughout this manual A warning means that injury or death is possible if the instructions are not obeyed A caution means that damage to the instrument or othe
65. t and observe the displayed value It should be within 10 mV of 0 000 V Select Measure It should also be within 10 mV of 0 000 V Select Output It should also be within 10 mV of 0 000 V Set the internal setpoint to 8 000 V by sending SETP 8 0 and repeat the previous three steps each time observing that the displayed value is within 10 mV of 48 000 V Set the internal setpoint to 8 000 V by sending SETP 8 0 and repeating the same three measurements each time observing that the displayed value is within 10 mV of 8 000 V Now disconnect the Output from the Measure input and ground the Measure input using a BNC grounding cap or 50 Ohm terminator Turn off I control using ICTL OFF and turn on P control using PCTL ON The P gain parameter should still be 8 0 Change the internal setpoint to 0 000 V using SETP 6 and select the P x e display level The value displayed should be within 50 mV of 0 000 V Now change the internal setpoint to 1 000 V using SETP 1 The P x e value should be within 50 mV of 8 000 V Change the internal setpoint to 1 000 V using SETP 1 The P x e value should be within 50 mV of 8 000 V 4 2 3 Proportional Gain Accuracy Reset the SIM960 via the remote interface using RST Ground the Measure input Connect the Source output of the SR785 to the SR785 Channel 1A input and to the SIM960 Setpoint input Connect the SIM960 ouput to the SR785 Channel 2A input With the SR785
66. terface commands 3 20 Status Model 2 4 ass 9 S 3 25 3 5 1 7 tatis Byte SB W ouo fave Ae ud 3 26 3 5 2 Service Request Enable SRE 3 26 3 5 8 Standard Event Status ESR 3 27 3 5 4 Standard Event Status Enable ESE 3 27 3 5 5 Communication Error Status CESR 3 27 3 5 6 Communication Error Status Enable CESE 3 28 35 7 Instrument Status INCR 3 28 3 5 8 Instrument Status INSR 3 29 3 5 9 Analog to Digital Status Enable INSE 3 29 3 5 10 Analog to Digital Status ADSR 3 29 3 5 11 Analog to Digital Status Enable ADSE 3 30 3 2 Remote Operation 3 1 Index of Common Commands symbol definition ij Integers f g Floating point values z Literal token Required for queries illegal for set commands var Parameter always required var Required parameter for set commands illegal for queries var Optional parameter for both set and query forms Controller Settings PCTL z ICTL z DCTL z OCTL z GAIN f APOL z INTG f DERV f OFST f 3 10 3 10 3 10 3 10 3 10 3 11 3 11 3 11 3 11 Proportional action ON OFF Integral action ON OFF Derivative action ON OFF Offset ON OFF Proportional Gain Controller Polarity Integral Gain Derivative Gain Output Offset Controller Configuration AMAN z 3 12 Output Manual Output PID Control INPT z 3 12 Input I
67. tleast one hour to warm up after power is turned on and care should be taken not to constrict the ventillation holes in the SIM900 mainframe It should be located in a room with stable temperature preferably from 65 to 75 degrees F The various subsystems of the SIM960 can be tested with the fol lowing procedures In all cases if the measurement is outside the tolerance or range indicated then the SIM960 is out of calibration 4 2 1 Input Amplifier Offset Ground the two inputs Setpoint and Measure of the SIM960 using BNC grounding caps or 50 O terminators Using the remote interface reset the SIM960 using the RST command Select External by pressing Setpoint on the front panel Adjust the P gain parameter to 1000 maximum gain Use the Multimeter to measure the Error output at the rear panel BNC of the SIM960 Switch the polariy of the P gain parameter and observe the change at the rear panel Error BNC The readings for both polarities should be within 10 mV of Zero 4 2 2 Ato D Converter test e Reset the SIM960 using the RST command ASRS SIM960 Analog PID Controller 42 Performance Tests Set the P gain parameter to 8 using GAIN 8 9 Turn off P control using PCTL OFF Set the I parameter to 10 using INTG 1 0E5 Turn on I control using ICTL ON Use a short BNC cable to connect the SIM960 Output to the Measure input Select Internal by pressing Setpoint on the front panel Select Setpoin
68. ton Query the last button that was pressed The values returned are Value Button 0 no button pressed since last LBTN 1 Setpoint 2 Output 3 Ramp Start Stop 4 Shift 5 Select 6 On Off 7 UJ 8 M Example LBTN 5 SIM960 Analog PID Controller ASRS Remote Operation Token Mode Set query the Token Query mode to Z OFF 0 ON 1 If TOKN ON is set then queries to the SIM960 that return tokens will return the text keyword otherwise they return the decimal integer value Thus the only possible responses to the TOKN query are ON and 9 At power on TOKN is set to OFF Example TOKN OFF TERM z Response Termination Set query the term sequence to Z NONE 8 CR 1 LF 2 CRLF 3 LFCR 4 The term sequence is appended to all query responses sent by the module and is constructed of ASCII character s 13 carriage return and 10 line feed The token mnemonic gives the sequence of characters At power on the default is TERM CRLF Example TERM 3 ASRS SIM960 Analog PID Controller 3 5 Status Model 3 25 3 5 Status Model The SIM960 status registers follow the hierarchical IEEE 488 2 for mat A block diagram of the status register array is given in Figure3 1 undef pa Eg Instrument Status undef undef 7 7 7 ADOUT Output Mon 3 undef 6 6 HH 6 ADERR Error Signal Mon 2 undef 5 5 5 ADMEAS Measure Mon RSTOP 4 4 4 ADSETP Setpoint Mon
69. version completion for one of SIM960 Analog PID Controller fs RS 3 30 Remote Operation the 4 monitored analog signals Bits in the ADSR are cleared only by reading or with the CLS command Reading a single bit with the ADSR i query clears only bit i Weight Bit Flag 1 0 ADSETP 2 1 ADMEAS 4 2 ADERR 8 3 ADOUT 16 4 undef 0 32 5 undef 0 64 6 undef 0 128 7 undef 0 ADSETP Setpoint Monitor Conversion Complete Indicates a new con version result is available for SMON ADMEAS Measure Monitor Conversion Complete Indicates a new con version result is available for MMON ADERR Amplified Error Monitor Conversion Complete Indicates a new conversion result is available for EMON ADOUT Output Monitor Conversion Complete Indicates a new con version result is available for OMON While reading this register with the ADSR query will clear any Tripn bit s that are set it will not reset the overvoltage protection circuit To do that the user must issue the TRIP command As long as a channel remains tripped off the Tripn bit will continuously be reasserted 3 5 11 Analog to Digital Status Enable ADSE The ADSE acts as a bitwise AND with the ADSR register to produce the single bit ADSB message in the Status Byte Register SB It can be set and queried with the ADSE command This register is cleared at power on SRS SIM960 Analog PID Controller 4 Performance Te

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