KEI 228A REF GUIDE
Contents
1. for Vcg Ic curves for the 253055 Most curves illustrated data manuals show the maximum safe forward bias area This area is self explanatory and should not be exceeded Figure 8 shows a typical structure of Vcg Ic curves Also shown in Figure 8 is the maximum safe forward bias area 18 COLLECTOR CURRENT 20 2N3055 MJ2955 ED IE ee ed 0 89 BERN NG COLLECTOR EMITTER VOLTAGE VOLTS A BONDING WIRE LIMITS THERMALLY LIMITED Tc 25 C SIGNAL PULSE Es SECOND BREAKDOWN LIMITS NOTE 228 HAS 20msec MINIMUM DWELL TIME Figure 8 Transistor Curves For incoming inspection testing manual testing may not be cost effective The configura tion shown in Figure 7 may be connected to the IEEE 488 bus and a computer The Model 228 has a built in IREE 488 interface that allows the test circuit to be incorporated into the measurement system Figure 9 shows the configuration with Model 228s connected to a computer over the IEEE 488 bus 19 CONTROLLER IEEE 488 BUS 22 MODEL 228 2 MODEL 228 1 Figure 9 Automated Test Set Up Using the system configuration the computer can be programmed to control the testing automatically The Model 228 responds to IEEE 488 protocol concerning commands and data The following program sets two Model 228s to the user selected values With the configura tion shown in Figure 9 the NPN power transistor 2N3055 can be tested2. for several of its parameters Some of these tests inlcude e Secondary Breakdown Vcg versus Ic s DC Current Gain hpg versus Ic set VcE On Voltage Voltage versus Ic plot set Vee Collector Saturation Vcg versus Ip Ic plot Collector Cut Off Ic versus Vece plot The computer used for the example program is the HP 9816 The program can easily be adapted for voltage as well as current output from the Model 228 20 PROGRAM REMOTE 711 REMOTE 712 OUTPUT Z ss 3 QUTPUT Filia OUTPUT 12 s F 82 SELECT COLLECTOR CURRENT EXAMPLE 1 LAMF IT ER fe H Be Coe ma WA Ina ra INPUT OUTPUT PIIG SJT abs beans Se OUTPUT PRINT 1 SELECT BASE CURRENT EXAMPLE 3 SBMA 118 IHFUU C 126 GUTPUT Piss E scat ee 126 WAITS 148 OUTPUT 2 ss RAY 154 IH THE OPERATE MODE THE MODEL 223 DISPLAYS ACTUAL VALUES 168 PRINT SHOT THE PROGRAMMED VALDES 17H WAITS 120 OUTPUT riist i36 OUTPUT rigat 288 WAITS 216 OUTPUT Es 228 PRINT REPEAT TEST Y YES H THEN FRESS ENTERS INPUT At IF THEN Z IF ag HS THEN 26B E Cri Ta P ha Pita s r Fat OUTPUT 12 pART BA GUTPUT 2 8 Skr TURN OFF ALL OF THE TEST EQUIPMENT 215 C
3. multiple Model 228 s in series or parallel does not increase the sink capability Instead it increases the voltage or current source capability 24 The highest amount of voltage possible from multiple Model 228s is 200V This is due to the common mode voltage specification of 100V The common mode voltage of 100V must not be exceeded on either instrument Figure 13 shows the method of connecting two Model 228s in series to obtain a higher voltage Figure 14 shows the recommended method of con necting more than two Model 228s in series to obtain a higher voltage In Figure 14 there are three Model 228s The voltage obtained is not 300V The maximum is 200V For exam ple on the 10V 10A range 30V at 10A can be achieved Figure 13 Two Model 228s in Series 25 NOTE MAXIMUM COMMON MODE VOLTAGE IS 100V DIODES MUST BE RATED FOR TWO TIMES THE MAXIMUM VOLTAGE AND ONE TIME THE MAXIMUM CURRENT Figure 14 Multiple Model 228s in Series Higher current can be obtained by connecting multiple Model 228s in parallel Refer to Figure 15 Two supplies can be connected in parallel for higher current without any additional pro tection circuitry If more than two supplies are connected in parallel additional protection circuitry is required as shown in Figure 16 The diodes allow the supplies to output current but not to sink current In Figures 15 and 16 the supplies are set for remote sense The amount of current is limited to
4. not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument Products that consist of a circuit board with no case or chassis e g data acquisition board for installation into a computer should never require cleaning if handled according to in structions If the board becomes contaminated and operation is af fected the board should be returned to the factory for proper cleaning servicing Rev 10 99 CHAPTER 1 Introduction This booklet has been written to help the user understand the operation and specifications of the Model 228 Voltage Current Source The chapters in this booklet have been written to aid the user in some applications Terms relating to the V I source such as stability line regulation load regulation and sensing are defined in the glossary For a complete explana tion of the instrument including front panel controls and IEEE 488 bus operation refer to the Model 228 Instruction Manual Document Number 228 901 01 The Model 228 is a power supply that can source or sink electrical power These unique features set it apart from ordinary power supplies Actually because of the Model 228 s precision and wide dynamic range the term SOURCE is used to differentiate it from or dinary power supplies Most power supplies do what the name implies they supply power usually voltage or current The Model 228 is capable of precise control of voltage or current while sourcing or sinking
5. power is on Always place the instrument in standby after the measurement or test is complete Use cables for the output that have appropriate current and insulation rating For ex ample if 10V at 10A is to be produced or dissipated then the cables must be rated for that amount Also use insulated lugs for connections on the quick disconnect board The Model 228 is capable of producing several times its current rating for short periods of time Keep this in mind when choosing a load Brief bursts of high current are still enough to damage other instrumentation and cause serious injury Do not operate the Model 228 with the top and or bottom covers removed Lethal poten tials are present throughout the mainframe The covers must also be in place to allow proper air flow through the instrument Proper air flow is required to cool the instru ment during operation If proper cooling is impeded the instrument may overheat When connecting active circuits observe proper polarity sink mode A reversed polarity may allow the instrument to operate at the current limit of the output fuse 20A When using the Model 228 to sink power from an external source refer to the example program and Program 2 Sink in Section 3 of the Model 228 Instruction Manual The MODULATION and the I MONITOR terminals on the quick disconnect board are electrically shorted The OUT terminal is at a potential similar to the MODULATION and I MONITOR
6. the values of voltage and current set by the user For example if the Model 228 is set for 5V 1A a resistive load of 100 draws 100mA from the Model 228 In the operate mode the front panel display monitor shows 5 00V and 100A In this case the programmed parameters were not exceeded Therefore the output accuracy is in effect Compliance accuracy is in effect when the Model 228 is in the sink mode The sink mode occurs whenever the monitored voltage and current are of opposite polarity For example if the Model 228 is set for 5V 1 a 10V battery connected to the output terminals OUT connected to the positive of the battery OUT connected to the negative of the battery forces the output of the Model 228 to 10V 1A In this example the compliance accuracy becomes effective on current If the battery is connected across the output terminals with reverse polarity OUT connected to negative of battery OUT connected to positive of battery the Model 228 would be in voltage limit instead of current limit CAUTION Observe proper polarity when connecting active circuits such as batteries and power supplies to the Model 228 The stated accuracy specifications for output accuracy and compliance accuracy pertain to the source mode and sink mode respectively The output accuracy applies while sourcing power from the Model 228 The compliance accuracy applies while sinking power to the Model 228 Display Monitor Accuracy Accuracy refer
7. when connecting two power supplies in series Compliance Compliance is defined as the extent to which an output parameter voltage or current deviates from the programmed value without compromise of the output parameter e g For constant voltage operation current control yields to voltage control as long as the actual output current is within the range of IserrinG the program med setting to IserrincG the compliance setting Outside this range the current control circuit attempts to take control of the output away from the voltage control circuit Constant Voltage Current A constant current source can force current through a device under test almost independently of the load resistance A constant voltage source can deliver a voltage across a device almost independently of the load resistance Current Monitor The Model 228 output current is sensed internally and converted to the 1V full scale voltage This voltage is routed to the A D converter and circuitry but also is available to the user via the current monitor output terminals Dwell Time Dwell time is the time spent on a specific memory location Dwell time is used in the Single Step Single Cycle and Continuous memory control modes The range of dwell time is 20msec to 1000sec Floating Floating is the term used to describe a condition where a common mode voltage exists between earth ground and the instrument or conductor of interest Four Quadrant Operation In four qu
8. 28 stability in clude the following parameters e Warm Up Time Temperature Coefficient Power Coefficient Auto Cal Time Output Impedance Load Warm up time is the time it takes for the Model 228 s internal parts to reach a stable operating temperature The Model 228 is 100 functional shortly after power on However accuracy and stability are not specified until after the temperature has stabilized 10 minutes for rated accuracy Temperature coefficient is the additional uncertainty of the output and readback values caused by operating at ambient temperatures outside the normal 18 C 28 C range For example What is the expected accuracy of the 10V range at 35 C ambient temperature Additional uncertainty 0 1 C x 0 1 0 1V x 35 C 28 C 0 07 0 07V Accuracy 0 1 0 1V 0 07 0 07V 0 17 0 17V Auto calibration is performed during the power up sequence Calibration constants may change by 0 5 counts between auto calibrations The previous calibration constants may be used by pressing CANCEL while the Model 228 is displaying CAL External Current Monitor The current monitor can be used to obtain a faster and more accurate reading from the Model 228 than the front panel display A voltage level that is proportional to the current level can be monitored using the current monitor output All current ranges output 1V at full scale full scale is 100 of range The accuracy
9. 9 64 69 Fiat 2B WILOCRISSA 14 Rest House Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 Viale 5 Gimignano 38 20146 Milano 02 48 30 30 08 Fax 02 48 30 22 74 Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 Kriesbachstrasse 4 8600 Diibendorf 01 821 94 44 Fax 01 820 30 81 1 Fl 85 Po Ai Street Hsinchu Taiwan R O C 886 3572 9077 Fax 886 3572 903
10. ETTING OUT SOURCE OR SINK O OUT 100 0 10V RANGE 1050 1A RANGE VSETTING SETTING OUT Figure 1 228 Equivalent Output Circuit The Model 228 is a constant current voltage constant current source The load determines the mode of the Model 228 either constant voltage or constant current For example if the load is of high impedance the Model 228 is in the constant voltage mode with the load resistance determining the current mode If the load is of low impedance the Model 228 is in the constant current mode with the load resistor determining the voltage For exam ple if the Model 228 is programmed to 10V and 10A a load of more than 12 controls the current A load of less than 10 controls the voltage J 10V 2Q 20 load requires 5A V 10A x 0 52 5V 0 52 load requires 5A The preceding paragraph can be summarized as follows 228 setting gt _______ then the Model 228 operates as a constant voltage source 1228 setting Vo22gsetting R lt the Model 228 operates as a constant current source 1228 setting Where V The voltage setting on the Model 228 I The current setting on the Model 228 R Connected load Figure 2 shows the Model 228 using a resistive load line Figure 3 shows the general graph of operation for the Model 228 10 10 LOAD LINE V ZERO CURRENT ZERO VOLTAGE 115 DESTRUCT
11. IVE LIMIT CURRENT LIMIT PROGRAMMED VOLTAGE LIMIT PROGRAMMED CURRENT LIMIT PROGRAMMED VOLTAGE LIMIT PROGRAMMED 20A FUSE Operation 115V DESTRUCTIVE LIMIT G CURRENT LIMIT PROGRAMMED H VOLTAGE LIMIT PROGRAMMED CURRENT LIMIT PROGRAMMED J VOLTAGE LIMIT PROGRAMMED K L f fue gy 20A FUSE Figure 3 Graph o 11 Sensing Remote and Local The sense S and S terminals are located on the quick disconnect board The sense ter minals are used in the volts mode When a load is connected to the Model 228 there is an IR lead drop between the load and the Model 228 CAUTION Take care to connect the sense terminals S and S to the load with proper polarity Connect S to the positive terminal and 5 to the negative terminal Improper polarity may result in damage to the instrument and load The effects of sense current should be taken into consideration when making extremely sen sitive tests The sense current is small but it can still affect the potential that is delivered to the load To minimize the effects of the sense lead current keep the resistance of the output leads and sense leads low Sense current is typically less than 1004A see Figure 4 12 VOLTAGE TOTAL LEAD RESISTANCE E G IOUT 1 OUT LEADS ERROR 10002 1000 100 i OmV 1mV mA TOMA 100mA 1A TOA OUTPUT CURRENT Figure 4 Voitage Error Usin
12. Model 228A Voltage Current Source gt U p L T Tann sr Application amp Reference Guide Model 228A Voltage Current Source All references to the Model 228 apply also to the Model 228A 1985 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A Document Number 228A 904 01 WARRANTY Keithley Instruments Inc warrants this product to be free from defects in material and workmanship for a period of I year from date of shipment Keithley Instruments Inc warrants the following items for 90 days from the date of shipment probes cables rechargeable batteries diskettes and documentation During the warranty period we will at our option either repair or replace any product that proves to be defective To exercise this warranty write or call your local Keithley representative or contact Keithley headquarters in Cleveland Ohio You will be given prompt assistance and return instructions Send the product transportation prepaid to the indicated service facility Repairs will be made and the product returned transportation prepaid Repaired or replaced products are warranted for the balance of the original warranty period or at least 90 days LIMITATION OF WARRANTY This warranty does not apply to defects resulting from product modification without Keithley s express written consent or misuse of any product or part This warranty also does no
13. OMMENTS Set 228 1 to remote 1 Set 228 2 to remote Clear screen Set 228 1 to standby Set 228 2 to standby Input current value Set 228 1 to value selected Clear screen Input current value Set 228 2 to value selected t Wait 3 seconds Clear screen Wait 3 seconds before operate Set 228 1 to operate Set 228 2 to operate Wait 3 seconds Clear screen Input command If yes repeat If no go to line 210 Set 228 1 to standby Set 228 2 to standby Clear screen 21 Power Supply Testing The Model 228 is capable of acting as a source or as an accurate and stable load Power sup plies and batteries can be tested with the Model 228 acting as the load Controlled charge and discharge of batteries is a good application of the Model 228 The load conditions can be programmed over the JEEE 488 bus or from the front panel Figure 10 shows the con figuration of the Model 228 sinking power from the battery The battery in the figure is rated at 10V The Model 228 must be programmed for a voltage of less than 10V to operate in the sink mode When the voltage of the Model 228 is less than the voltage of the battery current is drawn from the battery into the Model 228 The COMPLIANCE graph shows that the instrument is operating in the sink mode The voltage is positive but the current is be ing drawn from the battery which shows up on the COMPLIANCE graph as nega
14. adrant operation voltage or current can be either positive or negative thus four combinations are possible Positive polarity of voltage and current is defined as source quadrants where power is delivered from the Model 228 to the user s load Opposite polarity of voltage and current V 1 or V 1 is de fined as sink quadrants where power from the user is dissipated in the Model 228 Impedance The effect of R L or C in series or parallel with the output This causes the output voltage or current to vary slightly when load changes occur Load The device to which power is delivered Load Line The load line is the operating line on the V vs I graph for a particular load Load Regulation Load regulation is the ability of the Model 228 to keep the output voltage or current constant when the load changes Modulation External External modulation is a low frequency DC to 600Hz low voltage 10V signal that is supplied by the user and is superimposed on the output signal of the Model 228 Operate Operate programs the output to the user selected values Standby programs the output to OV During operate the two displays show actual measured values of voltage and current During standby the programmed settings are displayed Quick Disconnect Board An output board that contains the OUTPUT SENSE EXTERNAL MODULATION and CURRENT MONITOR terminals This board fits into the re cessed slot on the rear panel o
15. and maintenance of equipment for ensuring that the equipment is operated within its specifications and operating limits and for en suring that operators are adequately trained Operators use the product for its intended function They must be trained in electrical safety procedures and proper use of the instru ment They must be protected from electric shock and contact with hazardous live circuits Maintenance personnel perform routine procedures on the product to keep it operating for example setting the line voltage or replac ing consumable materials Maintenance procedures are described in the manual The procedures explicitly state if the operator may per form them Otherwise they should be performed only by service personnel Service personnel are trained to work on live circuits and perform safe installations and repairs of products Only properly trained ser vice personnel may perform installation and service procedures Exercise extreme caution when a shock hazard is present Lethal voltage may be present on cable connector jacks or test fixtures The American National Standards Institute ANSI states that a shock hazard exists when voltage levels greater than 30V RMS 42 4V peak or 60VDC are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring Users of this product must be protected from electric shock at all times The responsible body must ensure that
16. f the Model 228 Response Time Response time is the time the Model 228 microprocessor takes to respond to a signal on the External Trigger input Response time is measured from trigger in put until the output has change 99 of the difference between the old memory step and the new memory step A range change polarity change or change between voltage and current extends the response time Self Test During the power on sequence the Model 228 tests memory RAM and ROM the A D converter control circuitry and power supplies During operation the Model 228 monitors temperatures power supplies and the A D converter If an error is discovered the Model 228 attempts to protect the user and itself Sense Local and Remote Remote sensing maintains regulation at the load instead of the output terminals of the Model 228 therefore compensating for the test leads IR voltage drop Local sensing maintains regulation at the output terminals of the Model 228 Source Vice Sink Source is a condition where in the Model 228 delivers power to the user s load Stability Stability is the ability to keep from changing Trigger IN amp OUT The TRIGGER IN and TRIGGER OUT connectors are female BNC con nectors that accept or output a negative going greater than 10usec TIL pulse The trigger input pulse starts the memory control mode The trigger output pulse appears at the TRIGGER OUT connector at the end of each programmed dwell time Standby Vice Ope
17. g Local Sensing 13 Load Regulation Also See Output Impedance Load regulation is the ability of the Model 228 to keep the output voltage or current con stant when the load changes Output resistance affects the final or steady state value of the ouptut for different loads Output impedance affects the amount of overshoot under shoot and settling time or dynamic response for a changing load The Model 228 s load regulation can be calculated using the following two methods 1 As a Current Source Figure 5 Model 228 as a Current Source Rour Cour make up the output impedance Static load regulation A Iour for different loads A Vour caused by different loads Rour For example 1A 100V range current regulation for no load to full load Full load Noload 100V 0V Alour _ ___ ____ mA 100kQ 100k 100kQ 14 The change in the load is 1000 to 00 A lout ImA OUT 100 lout 1A as a x 100 0 1 2 As a Voltage Source Figure 6 Model 228 as a Voltage Source Ro Lo make up the output impedance Static load regulation Vour for different loads Iour caused by different I Ro For example 100V 1A range voltage regulation for no load to full load A Vout 1A 0A x 0 0100 0 010V A Vour 0 010V x 100 Vout 100V as 100 0 01 Stability Stability is the ability to maintain consistancy Factors which affect Model 2
18. he current to the desired level This method is very simple and requires no additional circuitry The second method involves some external circuitry A resistor in series with the output zener diode across the output could be used as a high speed current voltage limit if these components have a sufficient power rating Changing the 20A output fuse to a lower value also helps to protect the user s circuitry The Model 228 is not a high speed pulse generator The fastest pulse that can be program med into the Model 228 is 20msec Secondary breakdown characteristics of semiconductors are normally specified in the range of microseconds Thus 20msec would be sufficient to destroy the device under test instead of testing the particular parameter Obtaining curves for bipolar transistors can be done using two Model 228 sources One source is connected between the base and emitter and the other source is connected between the collector and the emitter Figure 7 shows the configuration for obtaining the family of curves for a 2N3055 power transistor The curves shown represent the collector emitter voltage ver sus collector current Vcg Ic curves 17 MODEL 228 2 MODEL 228 1 Figure 7 Power Transistor Test Set Up 2N3055 The Model 228 is capable of producing 100W of power The power rating of the 2N3055 transistor is approximately 100W Therefore the Model 228 is ideal for testing such a wide ly used power transistor Refer to Figure 8
19. of the current monitor is the same as the constant current mode The current monitor is not connected to the 3 digit A D converter and therefore has a higher resolution than the front panel display Current monitor readings may be read back over the TEEE 488 bus eliminating the need for external metering The bandwidth of the current monitor is 5kHz typical The output resistance of the cur rent monitor is 10kQ The current monitor terminals are located on the quick disconnect board NOTE The current monitor floats at output LO OUT 16 CHAPTER 4 Applications The following applications show how the Model 228 could be used in several situations in cluding Making low resistance measurements conducting battery tests semiconductor testing and power supply testing Semiconductor Testing The Model 228 is suitable for testing many of the parameters of power semiconductors such as VMOS FETs diodes and bipolar transistors Typical curves for the transistors can be ob tained using one or two Model 228s The Model 228 supplies up to 100W of power for these applications Precautions The current voltage limiting of the Model 228 is not instantaneous The output capacitance inductance allows a brief current voltage surge before the current voltage limiting cir cuitry reacts There are two methods for dealing with this situation The first method is to simply start the measurement with zero current and gradually increase t
20. power In general instruments that are defined as power sources supply electrical power to a con nected load Some power sources can also act as a load for an external source This is generally known as sinking power There are numerous applications for an instrument that can sink power as well as supply power For example the Model 228 can charge then discharge a battery at a controlled rate There are three features that differentiate the Model 228 from power supplies 1 Multiple Ranges 2 Four Quadrant Operation 3 Constant Voltage Constant Current Glossary Accuracy Accuracy is defined as how close the actual output value reflects the programmed value Display monitor accuracy is defined as how close the display monitor reflects the actual output value Auto Cal The A D converter in the Model 228 measures various gains and offsets within the instrument With this information the microprocessor calculates calibration fac tors which it uses when programming the output Power on Program 6 and Program 9 all start the Auto Cal sequence Battery Back Up Values programmed into the 100 step memory are saved even when the AC power is turned off This is possible because the values are stored in CMOS memory which is powered by a rechargeable battery Common Mode Voltage Common mode voltage is the potential difference between earth ground and normally common output terminal of the Model 228 This voltage is normally generated
21. r jump ers installing or removing switching cards or making internal changes such as installing or removing jumpers Do not touch any object that could provide a current path to the common side of the circuit under test or power line earth ground Always make measurements with dry hands while standing on a dry insulated surface capable of withstanding the voltage being measured The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the equip ment may be impaired Do not exceed the maximum signal levels of the instruments and ac cessories as defined in the specifications and operating informa tion and as shown on the instrument or test fixture panels or switching card When fuses are used in a product replace with same type and rating for continued protection against fire hazard Chassis connections must only be used as shield connections for measuring circuits NOT as safety earth ground connections If you are using a test fixture keep the lid closed while power is ap plied to the device under test Safe operation requires the use of a lid interlock Ifa screw is present connect it to safety earth ground using the wire recommended in the user documentation The IN symbol on an instrument indicates that the user should re fer to the operating instructions located in the manual The A symbol on an instrument shows that it can source or mea
22. rate The standby mode programs the Model 228 to output OV and displays the programmed settings instead of the actual values Polarity and range changes are delayed until the OPERATE button is pressed Modulation is disabled in the standby mode Sink Vice Source Sink is described as the ability of the Model 228 to dissipate power sup plied by the user s circuit This includes discharging batteries inductive loads and capacitive loads Sink Only Sink only reduces internal dissipation so that a full 100W can be dissipated by the Model 228 for long periods of time even at high ambient temperatures with no derating Since this function reduces the Model 228 s sourcing capability 1 5A it should only be used when sourcing is not required CHAPTER 2 Safety Precautions The following information outlines general safety precautions that should be observed before during and after operating the Model 228 1 10 11 12 13 Before operation ground the Model 228 through a properly earth grounded receptacle Failure to ground the instrument may result in severe injury or death in the event of a short circuit or malfunction Never assume the output is at a safe potential while the AC line is connected Never come into contact with the output connections while the instrument is turned on Always set up the test circuit while power is turned off Do not come into contact with any part of the test circuit while
23. s to the output of the Model 228 The output value could differ from the pro grammed value by the specified accuracy The displayed value could differ from the output value by the specified accuracy The displayed readback of the output is approximately 2 times per second The pro grammed output is fast but has some inherent offset For steady output the display value is more accurate than the programmed setting For changing output the programmed set ting is precise while the displayed value requires sufficient time to assure steady state For example if the output is programmed for 1 000V with no load the output will be 1 000V 2mV If the output is 1 000V the display will read 1 000 2mV Times Programming time is stated as 30msec maximum from trigger to 99 of programmed change For example if 15V is present at the output and the instrument is programmed for 50V it will take the Model 228 30msec to reach 49 6V This specification applies when on the same range and polarity Time is measured from external input to settled output Load transient recovery time is specified with a resistive load only With a resistive load the output can recover 90 of any load changes within Imsec after the end of the changes This time is specified for the changes which do not cause transfer to another control mode i e voltage to current limit or source to sink AS A SOURCE 2 OUT serne 10042 10V RANGE 1A RANGE VS
24. sure 1000 volts or more including the combined effect of normal and common mode voltages Use standard safety precautions to avoid personal contact with these voltages The WARNING heading in a manual explains dangers that might result in personal injury or death Always read the associated infor mation very carefully before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the warranty Instrumentation and accessories shal not be connected to humans Before performing any maintenance disconnect the line cord and all test cables To maintain protection from electric shock and fire replacement components in mains circuits including the power transformer test leads and input jacks must be purchased from Keithley Instru ments Standard fuses with applicable national safety approvals may be used if the rating and type are the same Other components that are not safety related may be purchased from other suppliers as long as they are equivalent to the original component Note that se lected parts should be purchased only through Keithley Instruments to maintain accuracy and functionality of the product If you are unsure about the applicability of a replacement component call a Keithley Instruments office for information To clean an instrument use a damp cloth or mild water based cleaner Clean the exterior of the instrument only Do
25. t apply to fuses software non rechargeable batteries damage from battery leakage or problems arising from normal wear or failure to follow instructions THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE THE REMEDIES PRO VIDED HEREIN ARE BUYER S SOLE AND EXCLUSIVE REMEDIES NEITHER KEITHLEY INSTRUMENTS INC NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS INC HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES SUCH EXCLUDED DAMAGES SHALL INCLUDE BUT ARE NOT LIM ITED TO COSTS OF REMOVAL AND INSTALLATION LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON OR DAMAGE TO PROPERTY KEITHLEY Keithley Instruments Inc 28775 Aurora Road Cleveland OH 44139 440 248 0400 Fax 440 248 6168 http www keithley com BELGIUM Keithley Instruments B V Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 CHINA Keithley Instruments China Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 62022886 Fax 8610 62022892 FRANCE Keithley Instruments Sarl B P 60 3 all e des Garays 91122 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 GERMANY Keithley Instruments GmbH Landsberger S
26. terminals Shorting the OUT terminal to the MODULATION and or I MONITOR ter minals shorts the Model 228 s current limiting circuitry The current limiting circuitry will not function properly if the terminals are shorted Grounded equipment can cause this problem Example A grounded function generator connected to the modulation input of the Model 228 with a grounded oscilloscope connected across the output terminals of the Model 228 When using multiple Model 228 s do not connect the modulation inputs together or the current monitor outputs Remember that the OUT terminals and these other terminals are at similar potentials CHAPTER 3 Operating Considerations General Specifications For detailed Model 228 specifications refer to the instruction manual Specifications precede the Table of Contents Output amp Compliance Accuracy Accuracy is defined as the degree of uncertainty of a measure to a standard or true value There are two accuracy specifications to take into consideration when using the Model 228 compliance accuracy and output accuracy These two specifications are described in the following paragraphs Output accuracy refers to the programmed parameters of the Model 228 The programmed parameters are the values set for voltage and current These values are set by the user either by the use of front panel controls or over the TEEE 488 bus Output accuracy is in effect when the load does not cause the output to exceed
27. the number of supplies connected in parallel Each Model 228 can deliver up to 10A on the 10V 10A range Each additional Model 228 connected in parallel increases current capability another 10A For example if three Model 228s are con nected in parallel as shown in Figure 16 current capability is increased to 30A This rating is on the 10V 10A range The increase in current capacity applies to all the ranges of the Model 228 For example the 100V 1A range is increased to 100V 3A output 26 Figure 15 Configuring Two Model 228s for Higher Current Figure 16 Configuring Three or More Model 228s for Higher Current 27 KEITHLEY Service Form Modei No Serial No Date Name and Telephone No Company List all control settings describe problem and check boxes that apply to problem Intermittent A Analog output follows display Particular range or function bad specify 1 IEEE failure 1 Obvious problem on power up Batteries and fuses are OK I Front panel operational 1 All ranges or functions are bad Checked all cables Display or output check one CY Drifts I Unable to zero O Unstable CY Will not read applied input Overload JJ Calibration only U Certificate of calibration required Data required attach any additional sheets as necessary Show a block diagram of your measurement system including all instruments connected whether po
28. tive cur rent Discharge will stop when the battery voltage reaches the programmed voltage see Figure 11 QUICK DISCONNECT BOARD BATTERY MODEL 228 Figure 10 Battery Life Test 22 QUICK DISCONNECT BOARD w I OUT MODEL 228 Figure 11 Data Logging Configuration When using the Model 228 to test power supplies most power supplies would be damaged if external voltages or currents are forced upon them Figure 12 is a suggested protection circuit for the external power supply The two protection diodes in the circuit protect most supplies in the event one of the following situations occur 1 Incorrect Model 228 polarity 2 Improper power on sequence Model 228 before external supply 3 The Model 228 is programmed for excessive voltage 23 MODEL 228 USER SUPPLY PROTECTION FOR USER S SUPPLY Figure 12 Power Supply Protection Circuit Model 228 Extended Voltage and Current The Model 228 has several ranges that can be selected to suit a particular application The most power a Model 228 can produce is 100W This level of power can be obtained by 100V at 1A or 10V at 10A In general this power is enough for most applications Sometimes however a higher voltage or a higher current that is outside of the Model 228 specifications is required In these situations the Model 228 can be connected to another Model 228 for higher output of voltage or current NOTE Connecting
29. trasse 65 D 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 GREAT BRITAIN Keithley Instruments Ltd The Minster 58 Portman Road Reading Berkshire RG30 1EA 0118 9 57 56 66 Fax 0118 9 59 64 69 INDIA Keithley Instruments GmbH Flat 2B WILOCRISSA 14 Rest House Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 ITALY Keithley Instruments s r l Viale S Gimignano 38 20146 Milano 02 48 30 30 08 Fax 02 48 30 22 74 NETHERLANDS Keithley Instruments B V Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 SWITZERLAND Keithley Instruments SA Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 TAIWAN Keithley Instruments Taiwan I Fl 85 Po Ai Street Hsinchu Taiwan R O C 886 3572 9077 Fax 886 3572 903 10 99 Safety Precautions The following safety precautions should be observed before using this product and any associated instrumentation Although some in struments and accessories would normally be used with non haz ardous voltages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recog nize shock hazards and are familiar with the safety precautions re quired to avoid possible injury Read the operating information carefully before using the product The types of product users are Responsible body is the individual or group responsible for the use
30. users are prevented access and or insulated from every connection point In some cases connections must be exposed to potential human contact Product users in these circumstances must be trained to protect themselves from the risk of electric shock If the circuit is capable of operating at or above 1000 volts no conductive part of the circuit may be exposed As described in the International Electrotechnical Commission IEC Standard IEC 664 digital multimeter measuring circuits e g Keithley Models 175A 199 2000 2001 2002 and 2010 are Installation Category IJ All other instruments signal terminals are Installation Category I and must not be connected to mains Do not connect switching cards directly to unlimited power circuits They are intended to be used with impedance limited sources NEVER connect switching cards directly to AC mains When con necting sources to switching cards install protective devices to lim it fault current and voltage to the card Before operating an instrument make sure the line cord is connect ed to a properly grounded power receptacle Inspect the connecting cables test leads and jumpers for possible wear cracks or breaks before each use For maximum safety do not touch the product test cables or any other instruments while power is applied to the circuit under test ALWAYS remove power from the entire test system and discharge any capacitors before connecting or disconnecting cables o
31. wer is turned on or not Also describe signal source Where is the measurement being performed factory controlled laboratory out of doors etc What power line voltage is used Ambient temperature oF Relative humidity Other Any additional information if special modifications have been made by the user please describe Be sure to include your name and phone number on this service form KEITHLEY Keithley Instruments Inc 28775 Aurora Road Cleveland OH 44139 440 248 0400 Fax 440 248 6168 http www keithley com BELGIUM CHINA FRANCE GERMANY GREAT BRITAIN INDIA ITALY NETHERLANDS SWITZERLAND TAIWAN Keithley Instruments Keithley Instruments China Keithley Instruments Sarl Keithley Instruments GmbH Keithley Instruments Ltd Keithley Instruments GmbH Keithley Instruments s r l Keithley Instruments B V Keithley Instruments SA Keithley Instruments Taiwan Bergensesteenweg 709 B 1600 Sint Picters Leeuw 02 363 00 40 Fax 02 363 00 64 Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 lt 8610 62022886 Fax 8610 62022892 60 3 all e des Garays 91122 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 Landsberger Strasse 65 D 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 The Minster 58 Portman Road Reading Berkshire RG30 1EA 0118 9 57 56 66 Fax 0118 9 5
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