Home

Model 2790 Sourcemeter Switch system User`s Manual

1. INPUT H L SENSE H L CH21 H H CHI L L CH22 H H CH2 L L CH23 H H CH3 E L CH24 H H CH4 L L CH25 H H CH5 L L CH26 H H CH6 E L CH27 H H CH7 L L CH28 H H CH8 L L CH29 H H CH9 L L CH30 H H CHIO L L CH31 H H CHII L L CH32 H H CHI2 L L CH33 H H CH13 L L CH34 H H CH14 L L CH35 H H CHI5 L L CH36 H H CHI16 L L CH37 H H CHI7 L L CH38 H H CHI18 L L CH39 H H CHI9 E E CH40 H H CH20 L L AMPS41 H H AMPS42 E L Model 2790 SourceMeter Switch System User s Manual 3 9 Opening and closing 7702 channels Normally system channel operation is used to control 7702 input channels NOTE ltis not recommended but multiple channel operation can be used to control a 7702 module For multiple channel operation the 7702 module is controlled in basically the same way that a 7751 7752 7753 module is controlled see Section 2 except that multiple channel control ROUT MULT must be used to control the 7702 module More details on multiple channel operation is provided in Section 2 of the Model 2790 Reference Manual The following points summarize system channel operation Details on system channel operation for the 7702 module is provided in Section 2 of the Model 2790 Reference Manual When an input channel is closed for a 2 wire function a backplane isolation chan nel automatically closes to connect
2. Ground 0 OOD Doo 0 00 00 HI HI LO LO SRC SEN SRC SEN A B BANK 4 4 8 Model 2790 SourceMeter Switch System User s Manual Zippertubing shield A grounded wrap around shield for the wiring between the switching module and the test station should be installed The shield is a grounded metal foil that surrounds the bundle of wires The foil shield prevents damage to the wire insulation Grounding the shield to a safety earth ground provides extra protection in case a wire conductor becomes exposed It also serves to reduce measurement noise caused by EMI from nearby machinery A recommended shield is shown in Figure 4 5 It is a Zippertubing ZTZ SH3 series shield As shown the foil side wraps around the cable wires The shield is then held in place by fastener strips that zip together The ground wire of the shield is to be connected to a safety earth ground as shown in Figure 4 6 Figure 4 5 Zippertubing shield ZTZ SH3 series Zipper NOTE Drawing proportions are not scaled to actual length of the shield and ground wire Foil Wrapper gt To Inflator Test Signal Wires To Keith ley Switching Module Ground Wire Connect to a known safety earth ground Assembled Cable Bundle O OE O Model 2
3. Open all channels ROUT OPEN ALL Press OPEN gt select ALL Test step notes l Un BW WN Resetting the 2790 opens all channels and selects the DCV function auto range For remote programming RST places the 27790 in the one shot trigger mode For front panel operation FACT defaults places the 2790 in the continuous trigger mode This step closes the channels to connect the V source output to the DMM of the Model 2790 This step is optional Use it to verify that the correct channels are closed for the test For remote programming READ triggers and requests a single reading Always open all channels at the beginning and end of a test Cable discharge After using the V source of the 7751 7753 module a charge may be stored in the test cables and module signal paths The resulting voltage could ignite the inflator if it is con nected across a bridgewire Therefore a cable discharge circuit is used to safely dissipate the charge In brief cable discharge is automatically implemented when the OPEN ALL operation is performed As long as the test cables are connected to the module and the input channels 1 e channels 1 and 2 are closed all stored energy in the circuit will dissipate safely NOTE Details on the cable discharge circuit are provided in Section 2 NOTE The test procedure for HIPOT uses the OPEN ALL operation to perform cable discharge see steps 7 and 11 in Table 5 6 NOTE For high ohms me
4. 2 7 Enabling ohms math function ccscreisccncsnnsracenessenssatvasdnesnsiescues 2 11 Opening and closing channels cccccccccessccceeeeeeeeeeeeees 2 14 Viewing closed channels sasessstecscvescsantassmessdnamncataseateenencnans 2 15 Cable discharge CITCUIt ciuascceriutenea uisdomeladubteso din S ibt ei tM 2 18 Keithley 7702 Switching Module Simplified schematic of Keithley 7702 switching module 3 4 Q2 and thermistor TEMP connections eene 3 5 Q4 and RTD TEMP connections eeeeen 3 6 Current connections DCI and ACT eene 3 6 Voltage connections DCV or ACV eeeeeeeeeee 3 7 U SS NR ER RR REOR Pm 3 10 CLO C A m 3 10 COPING Re 3 11 Miewing closed channels ooo aero ios g ud 3g eiieeii 3 12 Using 7751 7753 V source with 7702 module dua qa FORO XOT catechins aset eheu EEEN 3 14 Switching Module Wiring and Installation Sorew terminal ACCESS ET E DO 4 3 Model 7751 7752 7753 screw terminal channel designations 4 5 Model 7702 screw terminal channel designations 4 6 Wire dressing 7751 7752 T153 assseestazssvucusuecetesov cac ze exusta 4 7 Zippertubing shield ZTZ SH3 series 4 8 Installed Zippertubing shield eeeessessss 4 9 5 Figure 5 1 Figure 5 2 Figure 5 3 Figure 5 4 Figure 5 5 Figure 5 6 Figure
5. Model 2790 SourceMeter Switch System User s Manual High ohms calculation Sx Vohms e SxVohms Calculates and displays the high resistance reading for the 7751 7753 module in slot x where x 1 or 2 This ohms function is a shortcut for the m X b calculation When selected the following m and b factors are used m 200 000 x Vsoug 7751 m 20 000 x Vsour 7753 b 0 7751 calculation R m X b 200 000 X Vsour VMEAS 0 VSOUR VMEAS X 200 000 7753 calculation R m X b 20 000 x Vsour VMEAS 0 VSOUR VMEAS X 20 000 where Vsoup is the programmed voltage level of the V source of the 7751 7753 For the 7751 200 000 x Vsoup is the m factor for the calculation m X b 200 000 is the value of the feedback resistor Rp for the I V amplifier Rp 200k 2 For the 7753 20 000 x Vsoup is the m factor for the calculation m X b 20 000 is the value of the feedback resistor Rp for the I V amplifier Rp 20kQ VMras i the output voltage of the V I amplifier measured by the DMM of the Model 2790 It is the X variable for the calculation m X b When the SxVohms calculation is selected the Model 2790 measures voltage X and calculates m X b using the above factors The displayed reading will be in ohms Q This selection also sets DMM to DCV 10V range Note that the Vmgas reading will be negative Because the output of the V I amplifier is inverted
6. KEI I HLEY Model 2 90 SourceMeter Switch System Users Manual A GREATER MEASURE OF CONFIDENCE Model 2790 SourceMeter Switch System User s Manual 2002 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A Third Printing September 2003 Document Number 2790 900 01 Rev C Manual Print History The print history shown below lists the printing dates of all Revisions and Addenda created for this manual The Revision Level letter increases alphabetically as the manual undergoes subsequent updates Addenda which are released between Revisions contain important change information that the user should incorporate immediately into the manual Addenda are numbered sequentially When a new Revision is created all Addenda associated with the previous Revision of the manual are incorporated into the new Revision of the manual Each new Revision includes a revised copy of this print history page Revision A Document Number 2790 900 01 eese March 2002 Revision B Document Number 2790 900 01 eese March 2002 Revision C Document Number 2790 900 01 ioiiieeeosvacst steU tee aei aeta tete E Re eses Eo September 2003 All Keithley product names are trademarks or registered trademarks of Keithley Instruments Inc Other brand names are trademarks or registered trademarks of their respective holders MaMalia4 Safety Precautions The following safety precautions should be observ
7. Provides the test circuit and procedure to measure the resistance of a shunt bar Bridgewire tests Provides the test circuit and procedure to measure bridgewire resistance of an inflator Insulation resistance HIPOT tests 7751 7753 only Provides the test cir cuits and procedures to measure the insulation resistance of an inflator Summa rizes cable discharge Includes tests for contact checks for high voltage connections and V source readback verification I source readback Shows how to use the I source readback circuit to verify the actual current flowing in the test circuit for bridgewire and shunt bar tests Memory patterns test Gives a test example using the memory patterns feature which can be used to simplify repetitive tests 5 2 Model 2790 SourceMeter Switch System User s Manual Introduction There are three primary tests for an inflator e Shunt bar test e Bridgewire test e Insulation resistance HIPOT test This section focuses on performing the inflator tests Details on the tests are provided in Section 1 WARNING Since the Model 2790 system is not an intrinsically safe device it is the responsibility of the user to ensure that external protection be provided either by an inherently safe electrical barrier and or a safety barrier around the DUT or airbag to prevent injury in case of detonation Test procedures Tables Test procedures for remote programming and front panel are pres
8. optional finished 5 16 Model 2790 SourceMeter Switch System User s Manual Table 5 2 cont Test procedure bridgewire Command Sequence Front Panel Operation 10 Perform READ Take reading from display measurement 11 Open all channels ROUT OPEN ALL Press OPEN select ALL Test step notes 1 Resetting the 2790 opens all channels selects the DCV function auto range and selects the I source of the 7751 7752 7753 module For remote programming RST places the 2790 in the one shot trigger mode For front panel operation FACT defaults places the 2790 in the continuous trigger mode 2 This step sets the I source to output 50mA which is a typical test current used for this test For front panel operation and a 7751 7753 module the V source output setting will be displayed after setting the I source output 3 This step selects the low resistance calculation R VMEAS ISOUR Selecting SIIOHMS sets DMM to DCV 1V range This step closes the channels to make the test connections for the bridgewire test It assumes a bridgewire is connected to Bank 1 of a 7751 7752 or 7753 This step is optional Use it to verify that the correct channels are closed for the test For remote programming READ triggers and requests a single reading Always open all channels at the beginning and end of a test This step closes the channels to make the test connections for the second bridgewire It assumes the
9. s Manual V source readback Test circuit The V source readback circuit is shown in Figure 5 11 Closing channels 13 18 21 22 and 23 routes the voltage to the DMM of the Model 2790 The DMM needs to be on the 1000V range to measure the maximum output of the 7751 7753 500V Figure 5 11 V source readback circuit Input Hi Selects V pere 2790 DMM Input Lo I V Amplifier amp Closed channel switch NOTE Each channel except channel 23 is a 2 pole switch Therefore when a 2 pole channel is closed two switches close Channel 23 is a 1 pole switch see schematic in Figure 2 1 Open switches not used in the test circuit are not shown Model 2790 SourceMeter Switch System User s Manual 5 23 Test procedure Perform the steps in Table 5 5 to verify the open circuit output of the V source Table 5 5 Test procedure V source readback Test Step Command Sequence Front Panel Operation Reset 2790 and RST Press SHIFT press SETUP select open all channels RESTORE FACT Close channels to ROUT MULT CLOS 113 118 121 Press CLOSE select MULTI select 113 connect V source 122 123 gt select 118 gt select 121 gt select 122 gt select 123 gt press EXIT Verify channels ROUT MULT CLOS Press SHIFT gt press CARD gt select VIEW that are closed gt select SLOT1 7751 or 7753 Press EXIT optional when finished Perform READ Take reading from display measurement
10. 10 Q 10 pA 10 Q Note 7 100 Q Note 7 100 mQ mA 10 nA 0 2 V 100 nA 0 05 V 1 0 pA 03 v 10 pA Lo v ACCURACY ppm of reading ppm of range ppm parts per million e g 10ppm 0 001 Input Resistance or Open Ckt Voltage gt 10 GQ gt 10 GQ gt 10 GQ 10 MQ 41 10 MQ 1 6 6 V 6 6 V 6 6 V 12 8 V 12 8 V 7 0 V 7 0 V 6 6 V 24 Hour 23 C 1 15 30 15 6 10 4 15 6 20 6 20 20 20 6 20 6 20 6 20 6 150 6 800 30 40 100 60 30 100 300 200 30 1000 15 90 Day 23 C 5 25 70 2959 7 20 5 45 9 3549 80 20 80 6 80 6 80 10 80 10 200 10 3000 30 100 100 300 80 300 800 500 80 1200 40 1 Year 23 C 45 30 70 30 7 30 5 5549 504 9 100 20 100 6 100 6 100 10 100 10 400 10 3000 30 100 100 500 80 500 800 800 80 1200 40 Temperature Coefficient 0 18 C amp 28 40 C 1 5 C 1 1 C 1 19 C 5 DAC 5 1 C 8 1 C 8 1y C 8 1y C 8 1 C 8 1y C 70 1 C 385 1 C 8 1y C 50 5 C 50 50 C 50 5 C 50 5 C Ratio Accuracy Accuracy of selected Channel Range Accuracy of Paired Channel Range Afa a Channel Average Displayed in C F or K Exclusive of probe errors Range 4 Wire RTD Resolution Accuracy 1 Year 23 C 5 C Temperature Coefficient 0 18 C amp 28 40 C 100Q
11. 5 34 Model 2790 SourceMeter Switch System User s Manual 6 Model 2790 DMM Ohms Functions Introduction Summarizes the differences between the methods used by the Model 2790 DMM and the 7751 7752 7753 modules to measure resistance 4 wire ohms Explains the benefits of using the 4 wire ohms technique to measure low resistance Offset compensated ohms Explains the offset compensated ohms feature which is used to cancel the adverse effects of offset voltages present in the test circuit Keithley 7702 module Shows how to use the ohms functions of the Model 2790 DMM with the 7702 module Keithley 7751 7752 and 7753 modules Shows how to use the ohms functions of the Model 2790 DMM with the 775 1 7752 7753 module 6 2 Model 2790 SourceMeter Switch System User s Manual Introduction As a general rule for testing inflators the programmable I source of the 7751 7752 7753 modules should be used to measure low resistance bridgwires and shunt bars The pro grammable V source of the 7751 7753 module should be used to measure insulation resis tance For other resistance measurements wiring harnesses fuse blocks switches relays etc an ohms function Q2 or 24 of the Model 2790 can be used Low ohms measurements The ohms functions of the Model 2790 provide better accuracy than the I source method used by the 7751 7752 7753 module However the test current used by the Model 2790 is fixed For the 100
12. Reset 2790 and open all RST Press SHIFT press SETUP select RESTORE channels FACT Select 22 SENS FUNC RES Press 22 Close channels to test HI ROUT MULT CLOS Press CLOSE select MULTI select contact for bridgewire A 101 114 118 101 gt select 114 gt select 118 gt press EXIT Verify channels that are ROUT MULT CLOS Press SHIFT gt press CARD gt select VIEW gt select closed optional SLOTI 7751 or 7753 Press EXIT when finished Perform measurement READ Take reading from display Open all channels ROUT OPEN ALL Press OPEN select ALL Close channels to test HI ROUT MULT CLOS Press CLOSE gt select MULTI gt select contact for bridgewire B 104 114 118 104 gt select 114 gt select 118 gt press EXIT Verify channels that are ROUT MULT CLOS Press SHIFT gt press CARD gt select VIEW gt select closed optional SLOTI 7751 or 7753 Press EXIT when finished Perform measurement READ Take reading from display Open all channels ROUT OPEN ALL Press OPEN gt select ALL Close channels to test ROUT MULT CLOS Press CLOSE gt select MULTI gt select housing contact 108 115 118 108 gt select 115 gt select 118 gt press EXIT Verify channels that are ROUT MULT CLOS Press SHIFT gt press CARD gt select VIEW gt select closed optional SLOTI 7751 7752 or 7753 Press EXIT when finished Perform measurement READ Take reading from display R
13. Switch System User s Manual When used with one or two switching modules the Model 2790 can be used to test inflators With a 7751 7752 7753 module the Model 2790 can safely measure the resistance of bridgewires and shunt bars With a Model 7751 or 7753 module the Model 2790 can use the high voltage method to measure the insulation resistance of an inflator The 7702 module can be used for ohms testing that requires 20 40 channels of 4 wire 2 wire measurements Key features Programmable I source The 7751 7752 and 7753 modules have a built in programmable current source 0 to 50mA This constant current source is used to measure the resistance of bridgewires and shunt bars The Model 2790 has a low ohms math function SxIohms It calculates using the programmed current and measured voltage and displays the resistance in ohms of the bridgewire or shunt bar X is the slot number of the module being used Programmable V source The 7751 and 7753 modules have a built in program mable voltage source 50 to 500V and an I V converter to measure the insulation resistance of an inflator Current through the insulator is applied to the I V con verter where it is converted to a voltage that is measured by the Model 2790 The Model 2790 has a high ohms math function Sx Vohms It calculates using the programmed V source voltage and measured I V converter output voltage and dis plays the resistance in ohms of the insulation X is the s
14. a Model 2790 mainframe 7751 7752 7753 and 7702 modules can be purchased separately However this special order may require a longer delivery time and additional handling charges Test system A typical test system for airbag inflators includes a Model 2790 that is controlled by a PLC or PC and a device handler test station for the inflator The Model 2790 has two slots for switching modules Modules for testing inflators include the Models 7751 7752 and 7753 A Model 7702 module can also be used with the Model 2790 NOTE Only one Model 7753 module can be installed in a Model 2790 and it should be installed in slot 1 The 7753 can be installed in slot 2 but measurement accuracy might be adversely affected because cards are always calibrated in slot 1 Figure 1 1 shows a typical test system using a programmable logic controller PLC or a PC When using a PLC communications with Model 2790 are done over the RS 232 interface When using a PC communications with the Model 2790 can be provided using the GPIB or RS 232 Figure 1 1 System connections Device Handler Control Device Handler od Mechanical t RS 232 Keithley 2790 Slot 1 Cabling Connection MATH 7751 7752 ori Test Station 7753 Module with Interlock Interlock H PC Slot 2 GPIB DIGITAL O m mE RS 232 System KPCI 488 GPIB Expansion Interface IEEE 488 1 6 Model 2790 SourceMeter Switch System User s Manual Inf
15. 2 and 1k 2 ranges the test current is fixed at ImA Low ohms accuracy comparison e When using the current source of the 7751 7752 or 7753 module to perform 4 wire low ohms measurements accuracy is 0 09 50mA For the Model 2790 when using the 24 function 4 wire ohms 100 2 range and offset compensation basic resistance measurement accuracy is 0 0196 1 year spec Fuse resistance considerations Two fuses F3 and F4 are in series with the output of the on card current source to insure that the test current cannot exceed 62mA Fuses F1 and F2 are in series with the backplane connection to the meter INPUT HI For DMM resistance measurements these fuses are in series with the mainframe current source similar to F3 and F4 these fuses limit the main frame current output to a maximum of 62mA Because fuses F1 and F2 are in series with the DMM output they appear as lead resistance in a 2 wire measurement As a result the measured value of a short circuit connected to channels 1 2 4 5 7 8 10 or 11 and measured with the DMM in 2 wire ohms will basically equal the resistance of these fuses plus any additional trace and lead resistance The nominal cold resistance of a single fuse is about 5 5 2 Therefore when you measure a short through the 7751 7752 7753 modules using the DMM 2 wire ohms function for example contact checks you will actually read two times the fuse resistance plus any trace and other lead re
16. 2790 SourceMeter Switch System User s Manual 5 7 Dual stage inflator test connections Figure 5 4 Use this connection scheme if using a Keithley 7752 module It can also be used for the 7751 or 7753 module if not performing the HIPOT test Figure 5 5 Use this connection scheme if using a Keithley 7751 or 7753 mod ule It includes the connections for the HIPOT test Figure 5 4 Test connections shunt bar and bridgewire bar testing dual stage inflator Dual Stage Inflator A Shunt Bar Testing B Bridgewire Testing mrt ss ees es Uscccc7 5 5 1p 7 JHE GcZ Keithley 7751 7752 or 7753 UJ E SES No Bank 1 J101 SRC HI OOK o Ch 1 O SEN HI OVW SRC LO om OT SEN LO OVS ii SRC HI n2 E SEN HI O SRC LO O NOTE Some wires are shown in bold Ch 5 to make it easier to follow the SEN LO O signal paths GO GO 5 8 Figure 5 5 Model 2790 SourceMeter Switch System User s Manual Test connections shunt bar HIPOT and bridgewire testing dual stage inflator Keithley 7751 7753 Bank 1 J101 SRC HI Q Ch 1 SEN HI ONS SRC LO ane Qo SEN LO ONS S oo lvo e em Tal No SRC HI Ch 4 SEN HI SRC LO Ch O OJO O SEN LO Ch 6 4 o o DODIOS J e om W SRC HI SEN HI SRC LO SEN LO o olo ooo DODIOS Dual Stage Inflator A Shunt Bar and B Bridgewire Testing HIPOT Testing Built in shunt Available for use during HIPOT testing Cha
17. MULT CLOS Verify channels that are closed optional Press SHIFT press CARD select VIEW select SLOTI 7751 7752 or 7753 Press EXIT when finished Perform READ Take reading from display measurement Open all channels ROUT OPEN ALL Press OPEN select ALL Test step notes ie CSCO ANIHN MN BW WN Resetting the 2790 opens all channels and selects the DCV function auto range For remote programming RST places the 2790 in the one shot trigger mode For front panel operation FACT defaults places the 2790 in the continuous trigger mode This step selects the Q2 measurement function of the Model 2790 This step closes the channels to make the connections for the HI contact test This step is optional Use it to verify that the correct channels are closed for the test For remote programming READ triggers and requests a single reading Always open all channels at the beginning and end of a test This step closes the channels to make the connections for the housing contact test This step is optional Use it to verify that the correct channels are closed for the test For remote programming READ triggers and requests a single reading Always open all channels at the beginning and end of a test Model 2790 SourceMeter Switch System User s Manual 5 21 Table 5 4 Test procedure contact checks for dual stage inflator Test Step Command Sequence Front Panel Operation
18. Model 2790 or through a 7702 module these safety features are compromised creat ing the very real possibility of igniting the airbag Incorrect channel clo sures in the test system could inadvertently apply the external source to the inflator and ignite it Damage to the 7751 7752 7753 module may also occur if an external source is connected to it WARNING Since the Model 2790 system is not an intrinsically safe device it is the responsibility of the user to ensure that external protection be pro vided either by an inherently safe electrical barrier and or a safety bar rier around the DUT or airbag to prevent injury in case of detonation Setting source output levels I source and V source 7751 7753 output levels are set from the CONFIG item of the CARD menu The menu structure shown in Figure 2 2 is accessed by pressing and releasing SHIFT and then pressing CARD e source Set output from 0 to 50mA In the menu structure the I source is desig nated as channel 27 The default setting is ImA e V source 7751 7753 only Set output from 50 to 500V In the menu structure the V source is designated as channel 28 The default setting is 50V NOTE When using the V source as an independent source limit 7751 output current to SOWA or 7753 output current to 500uA to achieve rated accuracy Typical short circuit current is ImA Model 2790 SourceMeter Switch System User s Manual 2 7 Figure 2 2 Setting I source and V s
19. Source 4 Sense CH12 A4 B4 2 20 Model 2790 SourceMeter Switch System User s Manual Using memory patterns Firmware revision level Memory patterns are supported in Model 2790 units with firmware A04 and higher The firmware revision level is displayed as part of the power up cycle Overview Most Model 7751 7752 7753 tests follow the same basic procedure select a source and set its level configure the Model 2790 measurement close the necessary relays and take a read ing Memory Patterns simplify this process allowing you to store combinations of multiple closed channels source settings and DMM measurement configurations in nonvolatile memory Up to 40 such Memory Patterns designated M1 through M40 can be stored There is also memory pattern MO which is defined as an all open pattern Recalling MO opens all channels and resets all sources to their factory default values Similar to closing one 7702 channel and taking a reading you can recall an individual Memory Pattern to close multiple channels and take a reading More importantly you can include Memory Patterns in a scan list and cause the Model 2790 to automatically scan through the specified memory locations As each memory pattern is scanned the sources and DMM are configured appropriately the specified group of channels is closed and a reading is taken Reading limits can also be assigned to each memory pattern so that during a scan the readings
20. Specifications sheet Cable discharge 7751 7753 only channel 20 A cable discharge circuit is used to dissipate charge build up on the inputs to prevent acci dental ignition of the inflator For details see Cable discharge circuit e Closing channel 20 discharges voltage on the input channels Model 2790 SourceMeter Switch System User s Manual 2 5 Source readback channels 13 and 25 The actual output of the selected source can be verified by using source readback which routes the selected source back to the DMM of the 2790 for measurement I source and V source readback are explained in Section 5 e Opening channel 22 and closing channels 21 25 and 18 connects the I source sense resistor to the DMM of the Model 2790 Closing channels 22 21 13 and 18 connects the V source to the DMM of the Model 2790 Interlock J106 A 7751 7752 7753 module has an interlock to disconnect its I source and V source from the rest of the switch matrix In order to use the module sources interlock must be enabled The interlock switch of a test station is connected to the J106 terminals of the module When the interlock switch is open 1 e safety shield open the sources cannot be connected to the switch matrix Details on interlock are provided in Section 5 NOTE The Interlock switch does not affect the output of J107 Voltage can still be present at those terminals even if the interlock is disabled See General purp
21. System User s Manual Bridgewire test The air bag inflator has two terminals connected to a bridgewire which is coated with a primer that ignites when sufficient current passes through the wire The bridgewire s resis tance is typically from two to three ohms 2Q being the most common To avoid unintended ignition the level of test current applied is generally 50mA or less As shown in Figure 1 3 a fixed current is sourced through the bridgewire The voltage across the bridgewire is then measured by the DMM of the Model 2790 Figure 1 3 Bridgewire testing 7 Keithley 3 3 p4791 7752 or 7753 Module Bridgewire Under Test RBRID VMEAS SOURCE OUR DMM RBRID With the low ohms math function selected the Rppp reading can be read directly from the display of the Model 2790 I source readback Before performing the bridgewire test you can verify the actual current flowing in the test circuit by using the I source readback circuit NOTE Amore accurate ohms reading can be achieved using the 24 function of the Model 2790 ImA fixed See Section 6 for details Model 2790 SourceMeter Switch System User s Manual 1 9 Insulation resistance HIPOT test 7751 and 7753 only WARNING The Models 7751 and 7753 are provided with outputs that are poten tially hazardous if not connected properly It is the responsibility of the customer to operat
22. Vmeas Readback current Igp is then calculated using Ohms Law pp Vmeas 12 Make sure to open all channels before closing the appropriate channels for I source read back When finished make sure to again open all channels The mX b calculation can be used to read the I source current in amps by setting m to 1 0 and b to 0 0 Front panel operation Press SHIFT gt press MATH gt select mX B gt set M to 1 0 gt set B to 0 0 gt select UNITS A Remote programming CALC FORM MXB CALC KMAT MMF 1 CALC KMAT MBF 0 0 CALC KMAT MUN A CALC STAT ON e Model 2790 SourceMeter Switch System User s Manual 5 29 Figure 5 13 I source readback circuit A Test circuit for current source readback bridgewire 2790 DMM Keithley 7751 7752 or 7753 Bridgewire Under Test souRcE 69 Closed channel switch Ch 22 open l source selected Test assumptions To test inflator connected to Bank 1 close channels 1 and 2 To test inflator connected to Bank 2 close channels 4 and 5 NOTE Each channel except channel 24 is a 2 pole switch Therefore when a 2 pole channel is closed two switches close Channel 24 is a 1 pole switch see schematic in Figure 2 1 Open switches not used in the test circuit are not shown Test circuit for current source readback shunt bar 2790 DMM Keithley 7751 7752 or 7753 Shunt Bar Under Test ISOURCE Test assumption Shunt bar connect
23. before channel 121 so that the clamp is in place before connecting source to signal backplane Channels are closed in order listed 5 This step is optional Use it to verify that the correct channels are closed for the test For remote programming READ triggers and requests a single reading 7 Always open all channels at the beginning and end of a test 9 5 14 Model 2790 SourceMeter Switch System User s Manual Bridgewire tests NOTE The interlock of the 7751 7752 7753 must be enabled to use the I source Figure 5 6 shows how interlock is enabled Test circuit The circuit for an inflator bridgewire test is shown in Figure 5 8 Figure 5 8 Test circuit bridgewire tests 21 lor4 tor4 17 18 Input HI Bridgewire IsoURCE au 2790 DMM est Input LO LIU 69 Closed channel switch est assumptions To test bridgewire connected to Bank 1 close input channels 1 and 2 To test bridgewire connected to Bank 2 close input channels 4 and 5 NOTE Each channel is a 2 pole switch Therefore when a channel is closed two switches close see schematic in Figure 2 1 Model 2790 SourceMeter Switch System User s Manual 5 15 Test procedure Single stage inflator Perform Test Steps 1 through 7 in Table 5 2 Dual stage inflator Perform Test Steps 1 through 11 in Table 5 2 WARNING To prevent accidental ignition of the inflator ALWAYS open all chan nels in the test system at the beginning and e
24. cicecnscansestaracenscpcaratessnncasaiuadvanenvens 6 3 AEWA OMS aasasparassuncarersisalenisumat ani sahinseatutentanedsarcoreteantainencumasans 6 3 Offset compensated ohms sxctisrasascsarsxsnesienaueadaectoxsnencensinenstecnauees 6 5 Keithley 7702 MOOS serssesteicsrsscn ie e S knara 6 6 Keithley 7751 7752 and 7753 modules iioi Eoosacu cespite pete 6 8 Specifications Models 2790 7751 7752 717153 and 7702 lt siacesascsiessonseaavecsanss A 1 Ohms specification calculations 7751 7752 7753 A 8 TOVITI NI SIUS ENIRO T A 8 TOVITI WSOC ssie OEE A 9 1 Figure 1 1 Figure 1 2 Figure 1 3 Figure 1 4 2 Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 Figure 2 6 3 Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 Figure 3 5 Figure 3 6 Figure 3 7 Figure 3 8 Figure 3 9 Figure 3 10 4 Figure 4 1 Figure 4 2 Figure 4 3 Figure 4 4 Figure 4 5 Figure 4 6 List of Illustrations Test System Overview Systeni CONTE CHONS iesaveczc veas obus auibus edidi Rod Kota Papin FR Ea ERA 1 5 SKUT Dar Leste 2 555 9002 000 2000 008 68 60008 E eOUE RaRURGI OUR DRE 1 7 PSIG OC ye testing aosessionissus Gotued ca xtd rii 1 8 HIPOT testing 77531 7733 M 1 9 Keithley 7751 7752 and 7753 Switching Modules Simplified schematic of Keithley 7751 7752 and 7753 switching Modules a scesntccenonnnnmesanpanauanetitasanesoceoasaosavaseounctss 2 3 Setting I source and V source output levels
25. ohms performs two measurements using two differ ent test currents The two readings are then averaged to yield a single resistance reading NOTE Details on offset compensated ohms are provided in Section 3 of the Model 2790 Reference Manual Offset compensated ohms measurements can be performed on the 100 2 1K 2 and 10k 2 ranges for the Q4 function Front panel operation Perform the following steps to enable offset compensated ohms 1 Press 24 to select the 4 wire resistance function 4W annunciator on 2 Use the RANGE up and down keys to select the 1000 1kQ or 10k 2 range 3 Press and release SHIFT and then OCOMP to enable offset compensated ohms OCOMP annunciator on Remote programming The commands to control offset compensated ohms are listed in Table 6 1 Table 6 1 Commands to set offset compensated ohms SENSe 1 FUNCtion FRESistance lt clist gt Select 4 wire ohms function 24 FUNCtion lt clist gt Query function FRESistance RANGe n lt clist gt Select range 0 to 11e3 100e6 FRESistance RANGe lt clist gt Query 024 range FRESistance OCOMpensated lt b gt lt clist gt Enable or disable offset compensated OFF ohms ON or OFF FRESistance OCOMpensated lt clist gt Query state of OCOMP Suggested parameters SYSTem PRESet and RST disables offset compensated To select 100Q range let n 100 ohms and selects the 100M 2 range for
26. open disabled interlock does not dis able the sources The sources are always on and available at the J107 terminals of the module Interlock has no effect on the source outputs at J107 The selected source can also be accessed at JIO5 Source Hi and Source Lo when interlock is enabled With interlock open the sources are disconnected The interlock of the 7751 7752 7753 module must be enabled in order to connect the I source or V source 7751 7753 to the rest of the switch matrix With interlock disabled you will not be able to close switches that connect the selected source to the DUT and DMM The typical test station has a built in interlock switch which is to be connected to INTERLOCK of the 7751 7752 7753 When the test station lid or safety shield is open the switch will open to disconnect the sources of the 7751 7752 7753 Figure 5 6 shows how to connect the interlock of the 7751 7752 or 7753 to the test station Model 2790 SourceMeter Switch System User s Manual NOTE As shown in Figure 5 6 only connect a switch to J106 Do not connect any external sources to it The internal 5V source for interlock is referenced to chassis earth ground If the 5V terminal of J106 comes into contact with earth ground a fuse on the module will open After the fault is cleared the fuse will reset automatically With interlock open the following channels will open and cannot be closed e Channel 21 With this channel open the se
27. 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 accord ing to instructions If the board becomes contaminated and operation is affected the board should be returned to the factory for proper cleaning servicing Table of Contents 1 Test System Overview TOQUE TION o PT DN TRU MR M 1 2 4 3i cs Ar 1 2 Technica terms aout come uisu reen E EE 1 3 Model 2790 configurations eeeeeeseessssessssssssssssssssssssssssssssssseseeees 1 4 RCRUM E T UU UU TM 1 5 VE OP CS 0 RTT RT OO E 1 6 DUO DAE P reee EEEE A 1 6 Bidoewire TOS srssisenreniedieiior erise o En S E ETERS 1 8 Insulation resistance HIPOT test 7751 and 7753 only 1 9 2 Keithley 7751 7752 and 7753 Switching Modules Card COMPUT ALON acssescsonsesecaoniccupsssohsaiasianesatontemonsaiasehaamaeesiaaeue 2 2 I source channels 21 22 24 and 27 2 4 V source and I V amplifier 7751 7753 only channels 21 22 8 rae E vivpR NUES Ud 2 4 Cable discharge 7751 7753 only channel 20 2 4 Source readback channels 13 and 25 2 5 Tntedock J 100 T 2 5 General purpose terminal blocks J105 J107 and J108 2 5 Safety Warnings apie stcuwstanndteseatinasionannnssiesinsnenesasenawincaasnosnseeenetes 2 6 Setting source output levels ss
28. patterns test example using individual memory pattern recall RST ROUT MEM CLE ALL Set up memory location I ROUT MEM CHAN 1 101 114 118 ROUT MEM DEL 1 0 ROUT MEM READ STAT 1 ON SENS FUNC RES M1 SENS RES RANG 100 M1 SENS RES NPLC 1 M1 Set up memory location 2 ROUT MEM CHAN 2 104 114 118 ROUT MEM DEL 2 0 ROUT MEM READ STAT 2 ON SENS FUNC RES M2 SENS RES RANG 100 M2 SENS RES NPLC 1 M2 Set up memory location 3 ROUT MEM CHAN 3 108 115 118 ROUT MEM DEL 3 0 ROUT MEM READ STAT 3 ON SENS FUNC RES M3 SENS RES RANG 100 M3 SENS RES NPLC 1 M3 FORM ELEM READ Recall memory locations trigger request readings ROUT MEM REC 1 READ ROUT MEM REC 2 READ ROUT MEM REC 3 READ Restore GPIB defaults Clear all memory pattern locations Set channels 1 14 and 18 for memory location 1 Set delay to 0 Enable reading Select 2 wire ohms Select 100Q range Select 1 PLC Set channels 4 14 and 18 for memory location 2 Set delay to 0 Enable reading Select 2 wire ohms Select 100 range select 1 PLC Set channels 8 15 and 18 for memory location 3 Set delay to O Enable reading Select 2 wire ohms Select 100 range Select 1 PLC Send readings only from buffer Recall memory pattern 1 Trigger and request reading Recall memory pattern 2 Trigger and request reading Recall memory pattern 3 Trigger and request reading
29. platinum PT100 D100 F100 PT385 PT3916 or user type Offset compensation On 200 C to 630 C 0 01 C Thermistor 2 2kQ 5kQ and 10kQ 8 0 01 C 80 C to 150 C DC Speed vs Noise Rejection Rate 10 1 0 1 0 01 Readings s 0 01 0 08 15 12 500 400 2000 1800 0 06 C 0 08 C RMS Noise Digits 10V Range 6 5 lt 12uV 6 5 lt 4uV 5 5 lt 22 uV 4 5 lt 150 uV 0 003 C C 0 002 C C NMRR 110 dB 90 dB CMRR 120 dB 120 dB 80 dB 80 dB Average Accuracy Accuracy of selected Channel Range Accuracy of Paired Channel Range DC Operating Characteristics 60Hz 50Hz Operation Function DCV DCI Ohms lt 10M Thermistor 4W Ohms lt 10M RTD Channel Ratio Channel AVG Digits 6 5 15 Res 6 51 15 5 5 15 5 5 16 Sue 4 5 6 6 5 6 5 aS 6 5 6 5 5 515 16 Readings s 5 4 30 Q4 50 40 100 80 200 400 2000 1800 14 1 1 15 12 33 25 0 9 0 7 8 6 4 18 14 4 25 2 15 12 25 20 PLCs 10 I 1 0 1 0 1 0 1 0 01 10 1 0 1 10 1 0 1 10 1 0 1 HW 11 04 03 Rev D 2790 SourceMeter Switch System Specifications MAINFRAME FUNCTION SPECIFICATION DC System Speeds x RANGE CHANGES 50 s 42 s FUNCTION CHANGES 50 s 42 5 AUTORANGE TIME lt 30ms ASCII READINGS TO RS 232 19 2k BAUD 55 s MAX INTERNAL TRIGGER RATE 2000 s MAX EXTERNAL TRIGGER RATE 375 s DC MEASUREMENT CH
30. the input to the DMM of Model 2790 Example With the 22 function selected closing channel 1 also closes channel 45 When an input channel is closed for a 4 wire function or operation the two back plane isolation channels and the 2 pole 4 pole relay also close to connect the input to the DMM Example With the 24 function selected closing channel 1 also closes channel 21 paired channel 45 backplane channels and 43 2 pole 4 pole relay While in the normal measurement display state only the input channel that is closed is displayed on the Model 2790 For a 4 wire operation the paired input channel is not displayed Only one input channel and its paired input channel for 4 wire can be closed at the same time When you close another input channel the previous input channel opens Channel assignments To control the appropriate switching module the slot number must be included with the switching module channel number The channel assignment is formatted as follows SCH where S 1s the slot number 1 or 2 CH is the channel number Examples 101 Slot 1 Channel 1 218 Slot 2 Channel 18 Model 2790 SourceMeter Switch System User s Manual Front panel operation For system channel operation there are two methods to close an input channel You can use the and P keys or the SINGLE option for the CLOSE key The OPEN ALL option for the OPEN key opens all channels and p gt keys These front panel keys Figu
31. uV 750 000 V 1 0 nV Temp Coeff C 0 035 0 003 0 005 0 003 0 006 0 005 0 01 0 006 0 03 0 01 3 Hz 10 Hz 10 Hz 3 kHz 3 kHz 5 kHz Current 1 000000 A 1 0 pA 90 Day 1 Year 0 30 0 04 0 10 0 04 0 14 0 04 3 00000 A 10 pA 0 35 0 06 0 15 0 06 0 18 0 06 Temp Coeff C 0 035 0 006 0 015 0 006 0 015 0 006 3 Hz 500 kHz 333 ms 2 ps Frequency 100 mV 0 333 ppm 90 Day 1 Year 80 ppm 0 333 ppm SLOW 1s gate and Period to 3 33 ppm 80 ppm 3 33 ppm MED 100ms gate 750 V 33 3 ppm 80 ppm 33 3 ppm FAST 10ms gate Additional Uncertainty of reading Frequency and Period Low Frequency Uncertainty MED FAST MEASUREMENT METHOD Reciprocal Counting technique 0H 30H O28 GATE TIME SLOW 1s MED 100ms and FAST 10ms 30Hz 50Hz 0 50Hz 100Hz 0 1 0 AC General 100Hz 200Hz 0 0 18 AC CMRR 70dB 200Hz 300Hz 0 0 10 MAXIMUM CREST FACTOR 5 at full scale gt 300Hz 0 0 VOLT HERTZ PRODUCT lt 8 x 10 er E n x AC OPERATING CHARACTERISTICS Additional Uncertainty 0 05 0 15 0 30 60Hz 50Hz Operation AC MEASUREMENT CHARACTERISTICS Function Digits Readings s Rate Bandwidth ACV ACI 6 55 2s Reading SLOW 3 Hz 300kHz AC Volts 6 5 14 1 1 MED 30 Hz 300kHz 9 MEASUREMENT METHOD AC coupled True RMS O ne seed 6 5 35 28 FAST 300 Hz 300kHz INPUT IMPEDANCE 1MQ 2 by lt 100pF RO TT requency E INPUT PROTECTION 1000Vp or 400VDC 300Vrms with 7702 ae D ur e 5 5 9 9 MED 30Hz 3
32. voltage across the DUT is not sensed through the fuse resistance see Fuse resistance considerations page 6 2 so that measurement accuracy is not affected by fuses Figure 6 5 Using Model 2790 4 wire ohms with 7751 7752 7753 module low ohms measurements Keithley 2790 Fuse Keithley 7751 7752 7753 Resistance Input HI I M p o t Source HI eS Sense HI 19 DMM DUT Sense LO I eur LO Q L Input LO iSource LO Ch 11 9 Channel closed by user multiple channel operation Model 2790 SourceMeter Switch System User s Manual 6 9 Figure 6 6 shows the simplified test circuit for using the 22 function of the Model 2790 with the 7751 7752 7753 module to measure high ohms DUT e insulation resistance up to 120M2 The DUT is connected to channels 10 and 11 Bank 4 of the 7751 7752 7753 To connect the DUT to the DMM of the Model 2790 channels 10 11 13 and 18 must be closed Note that the voltage across the DUT is sensed through the fuse resistance so that measurement accuracy can be affected by fuses when making low ohms measurements NOTE When using the 2 wire ohms function of the Model 2790 to measure a resistance through one of the 775X modules there will be an offset in the measured value due the signal path resistance of the 775X module see Fuse resistance consid erations on page 6 2 This path resistance is due to safety circuitry fuses in the module The offset can be correc
33. with the message 1 7753 ONLY displayed and all annunciators will turn on In this case you must remove one module and cycle power to continue Installation procedure A Keithley switching module simply slides into one of two slots in the rear panel of the Model 2790 1 Turn off the Model 2790 and make sure there is no external power connected to it or the module External sources should never be used anywhere in the test system to take advantage of the 2790 improvements that reduce the risk of airbag detonation If a slot cover is installed remove it and retain for future use 3 With top cover side up slide the connector end of the module into the mainframe Make sure the front edge of the card is in the track for the slot 4 Push the module all the way in until it mates with the backplane connector of the mainframe 5 Hand tighten the two screws that secure the module in the mainframe Tightening these screws connects the module to chassis ground Inflator Testing Introduction Summarizes the tests used for airbag inflators and provides notes that apply to most tests Test system Shows a typical system connection using a programmable logic controller PLC and a PC Test signal connections The four basic system test connection schemes for inflator testing Interlock Covers interlock which is used to disconnect the sources of the 7751 7752 and 7753 modules from the switch matrix Shunt bar test
34. 0009 0020800SUBUSDA S GRE i ed aneio 5 2 Closed channels for test circuits 1 oodd trente 5 3 A E MT TU MM 5 3 RS 232 interface PLC or PC 14 eere orto not hae breit de ovn 5 4 GPT PC Only 5 55 55580 9 2020 99820 000 0 0000 0e inarin 5 4 Test signal connections oce posce kt sas scc iua vadat veau gua bes Oe EUR dim Be ERRARE EMOE UE 5 5 los di e T 5 0 Shunt Dar GSE csensencer ser n EER 5 10 T E 5 11 JTeSL DEO UUEE ericeira 5 12 J so rfc readback T oidedh 5 12 PIGS Me SIS uiosutstoscdubedietixincu mua EEEa oor SUE 5 14 MCSE CUCL aea 5 14 Toi ROC COUR derece ein r attended bu ea ago eR Desde 5 15 I soutc TEAC DACK serrr an 5 16 Insulation resistance HIPOT tests 7751 7753 only 5 17 Contact checks eeeseeeeeeeeeeeeeeen nennen 5 18 NSSDUEGO readbatk uo eisnisestein iv ninndiana 5 22 Cable GISC MAES e sucsccacinntataciansentceceeseueveebtuesutusentdadesueiocertebue 5 23 EIPCOT385E ea aM DM M M ME PUEDE 5 24 Test procedure HIPOT 4 25252 eo rire retorno trito 5 26 I ourccte3dbdOo E uesnutetem duse iive i cMbu Meddnttes ima UM DENM DUE 5 28 Memory patterns test iccccactccensesssicoaincessedsetawsttcedereistusdvameusdeciesse 5 30 l eem 5 30 Test procedure Me dini eni 5 31 Model 2790 DMM Ohms Functions PIERO GNC ON suraose ii 6 2 Low ohms measurements eeeeeeeeeeeen eene 6 2 Fuse resistance considerations eee 6 2 High ohms measurements
35. 00kHz 4 5 35 35 FAST 300 Hz 300kHz AC Current 4 5 65 65 FAST 300 Hz 300kHz MEASUREMENT METHOD AC coupled True RMS SHUNT RESISTANCE 0 10 BURDEN VOLTAGE 1A 0 3Vrms 3A 1 Vrms Add 1 Vrms when used with 7702 modules INPUT PROTECTION 3A 250V fuse HW 11 04 03 Rev D 2790 SourceMeter Switch System Specifications MAINFRAME FUNCTION SPECIFICATION AC System Speeds RANGE CHANGES 4 s 3 s FUNCTION CHANGES 4 s 3 s AUTORANGE TIME lt 3s ASCII READINGS TO RS 232 19 2k baud 50 s MAX INTERNAL TRIGGER RATE 300 s MAX EXTERNAL TRIGGER RATE 250 s AC Notes 2096 overrange except on 750V and 3A Specifications are for SLOW mode and sine wave inputs gt 5 of range SLOW and MED are multi sample A D conversions FAST is DETector BANDwidth 300 with nPLC 1 0 3 Applies to 0 18 C and 28 40 C Specifications are for square wave inputs only Input signal must be gt 10 of ACV range If input is lt 20mV on the 100mV range then the frequency must be gt 10Hz Applies to non sine waves gt 5Hz and lt 500Hz Guaranteed by design for Crest Factors gt 4 3 For IkO unbalance in LO lead 7 Speeds are for 60Hz 50Hz operation using factory defaults operating conditions RST Autorange off Display off Limits off Trigger delay 0 Includes measurement and binary data transfer out GPIB 0 0196 of step settling error Trigger delay 400ms Trigger delay 0 10 Sa
36. 1 5 33 HIPOT 5 26 shunt bar 5 13 V source readback 5 23 Commands Multiple channel control 2 8 2 12 2 14 3 11 6 5 Connection log Model 7702 3 8 Model 7751 7752 2 19 Connections and wiring 4 2 Contact checks 1 10 discharge circuit 2 17 dual inflator 1 4 Errors 241 870 2 12 Front Panel 3 10 Open interlock errors 5 10 operation 2 11 message 2 16 opening and closing channels 2 13 view closed channels 2 15 remote programming test procedures 5 2 test procedure bridgewire 5 15 contact checks 5 20 5 21 5 31 5 33 HIPOT 5 26 shunt bar 5 13 V source readback 5 23 Fuse 6 2 GPIB 1 5 5 4 Guarding 4 9 Hardware missing 2 12 High ohms calculation 2 10 math function 1 10 I V converter terminals 2 6 Inflator tests 1 6 Installation 4 1 4 10 installation 4 10 Insulation resistance 1 2 Model 7751 5 17 Insulation resistance HIPOT test 1 9 Interlock 1 6 2 5 interlock errors 2 16 Invalid current error 2 12 I source output levels 2 6 readback 1 8 leakage resistance 1 9 Low ohms calculation 2 9 Manual cable discharge 2 18 Math 2 9 matrix backplane and guard terminals 2 5 Memory 2 21 2 22 2 23 5 30 memory 2 20 Memory patterns setting up 2 21 Model 7700 7702 and 7703 Introduction A 1 Model 7702 3 1 22 Wire and Thermistor connections 3 5 Q4 Wire and RTD connections 3 6 Channel assignments 3 9 Connection Log 3 7 Current connections AC or DC 3 6 opening and closing channels 3 9 screw term
37. 1 7753 V source High ohms specifications using the V source of the 7751 7753 are provided for the 500V and 50V settings Use the following formulas for other V source settings For measurements 1M to 10MQ Ohms accuracy of reading 1 1 15 VsouncE o Ohms offset 20kQ where Voourcg i the voltage output setting in volts Example Determine ohms accuracy for a V source setting of 100V of reading 1 1 15 100 1 1 0 15 1 25 Ohms accuracy 100V 1 25 20kQ A 10 Specifications Model 2790 SourceMeter Switch System User s Manual Ohms temperature coefficient TC of reading 0 02 1 VsGugcp C TC ohms offset 200Q C where Voourceg is the voltage output setting in volts Example Determine temperature coefficient for a V source setting of 100V of reading 0 02 1 100 9o C 0 02 0 01 C 0 03 C Ohms temperature coefficient 100V 0 03 200 2 C For measurements 10MQ to 100M 2 Ohms accuracy o of reading 1 1 60 VgourcE Ohms offset 20kQ where Voourcg i the voltage output setting in volts Example Determine ohms accuracy for a V source setting of 100V of reading 1 1 60 100 1 1406 1 7 Ohms accuracy 100V 1 7 20kQ Ohms temperature coefficient TC of reading 0 02 6 VogurcE C TC ohms offset 200Q C where Voourceg is the voltage output setting in volts Example De
38. 5 7 Figure 5 8 Figure 5 9 Figure 5 10 Figure 5 11 Figure 5 12 Figure 5 13 Figure 5 14 6 Figure 6 1 Figure 6 2 Figure 6 3 Figure 6 4 Figure 6 5 Figure 6 6 Inflator Testing Dy Ss CM COMMCCIIONG crcire inan en E a ieai 5 3 Test connections shunt bar and bridgewire testing single stage inflator iuis otii ec odo dads oaios 5 5 Test connections shunt bar HIPOT and bridgewire testing single stage inflator essssssssss 5 6 Test connections shunt bar and bridgewire bar testing dual stage inflator susci iii oec Eoup oon erR On EG cosuweca ES Gs 5 7 Test connections shunt bar HIPOT and bridgewire testing dual stage inflator eror rr rtt inc d cases vocas eis 5 8 Interlock connections uiucdicedvencciivou aa edebat enu Recreo 5 0 Test circuit shunt bar sicaccssacedaarcemcoashotnesuargsatorsstecsasesaudieand 5 11 Test circuit bridgewire tests 2 22 oorr roi rere oso kr Re 5 14 Test circuits contact check single stage inflator 5 19 Test circuits contact check dual stage inflator 5 19 V source readback circuit siscscsnsansssarscaarsascvesaascnacdasecnereoanideond 5 22 Test circ it HIPOT cieincttincsvcnctiwensrccvareiesucsbnausbinddovadesoncziiees 5 25 I source re dback CILCUIL secniecsssasansacnessopestoacucnsivonieucmnedoalansoes 5 29 Test circuits memory patterns dual stage inflator contact test si sacc
39. 790 DMM Test i i Input LO NOTE Each channel except channel 24 is a 2 pole Closed ch suut switch Therefore when a 2 pole channel is Closed channel switc closed two switches close Channel 24 is a Test assumption Shunt bar connected to Bank 1 1 pole switch see schematic in Figure 2 1 Channels 4 and 5 used for dual inflator where each bridgewire has its own shunt bar See Figure 5 8 5 12 Model 2790 SourceMeter Switch System User s Manual Test procedure Perform the steps in Table 5 1 to test the shunt bar on a single inflator The test current for this measurement cannot exceed 1mA due to the dry circuit hardware limit See Table 5 2 for an example of a test sequence for dual inflator I source readback The 7751 7752 and 7753 modules have source readback capabilities I source readback allows you to verify the test current used for the shunt bar test Details on I source read back are provided in the last topic in this section Model 2790 SourceMeter Switch System User s Manual 5 13 Table 5 1 Test procedure shunt bar Command Sequence Front Panel Operation 1 Reset 2790 and RST Press SHIFT press SETUP select open all channels RESTORE FACT 2 Set I source to SOUR CURR 0 001 127 Press SHIFT gt press CARD gt select 1mA CONFIG gt select SLOT1 7751 7752 or 7753 set I C27 to 01 00 mA press ENTER press EXIT or ENTER Select and enable CALC1 FORM S1
40. 790 SourceMeter Switch System User s Manual 4 9 Figure 4 6 Installed Zippertubing shield Test Station Ground wrap cable bund Es e Safety Earth Ground Keithley 7751 7752 7 53 or 7702 Guarding NOTE The typical high ohms measurement applications for the 7751 7753 V source does not require guarding Guarding only needs to be used for the most demand ing noisy situations or when measuring gt 1GQ which is the maximum resis tance specified for the 7751 7753 A second inner shield can be used for high ohms measurements that use the 7751 7753 V source and I V converter This guarded shield may reduce noise and cable leakage that could result in measurement errors The guard terminals are available at J105 and J107 Guard is connected to a shield that surrounds the Source Lo and Sense Lo test leads that connect to the housing of the inflator In Figure 5 3 Section 5 use the guard shield to surround the two wires that are con nected to Bank 3 J103 of the 7751 module This guard shielded wire pair should be positioned inside the main cable bundle whose shield is connected to safety earth ground The guard shield should be insulated with an outer jacket A second Zippertubing shield can be used as the guard shield WARNING The guard terminals are connected to the floating ground of the 7751 7752 7753 module Do not connect V source Hi to earth ground If V source Hi is connected to earth ground g
41. 8 Fax 82 2 574 7838 www keithley com Netherlands Gorinchem 0183 635333 Fax 0183 630821 www keithley nl Singapore Singapore 65 6747 9077 Fax 65 6747 2991 www keithley com Sweden Solna 08 509 04 600 Fax 08 655 26 10 www keithley com Taiwan Hsinchu 886 3 572 9077 Fax 886 3 572 9031 www keithley com tw Copyright 2003 Keithley Instruments Inc Printed in the U S A 9 03
42. ARACTERISTICS DC Volts A D LINEARITY 2 0 ppm of reading 1 0 ppm of range INPUT IMPEDANCE 100mV 10V Ranges Selectable gt 10GQ with lt 400pF or 1OMQ 1 100V 1000V Ranges 1OMQ 1 INPUT BIAS CURRENT lt 100pA at 23 C COMMON MODE CURRENT lt 500nAp p at 50Hz or 60Hz INPUT PROTECTION Front 1000V Rear 300V 7702 card only Resistance MAX 4WQ LEAD RESISTANCE 10 of range per lead for 100Q and 1kQ ranges 1kQ per lead for all other ranges OFFSET COMPENSATION Selectable on 4WQ 100Q 1kQ and 10kQ ranges CONTINUITY THRESHOLD Adjustable 1 to 1000 Q INPUT PROTECTION Front 1000V Source Inputs 350V Sense Inputs Rear 300V 7702 card only DC Current Shunt Resistors 100mA 3A 0 10 20mA 5 Input Protection 3A 250V fuse DC Notes 2096 overrange except on 1000V and 3A Add the following to ppm of range uncertainty 100mV 15ppm 1V and 100V 2ppm 100 30ppm lt 1IMQ 2ppm 10mA and 1A 10ppm 100mA 40ppm 42 measured with 10MQ input resistance DMM gt 10GQ DMM on 10M and 100MQ ranges Relative to calibration accuracy gt For signal levels gt 500V add 0 02ppm V uncertainty for portion exceeding 500V Specifications are for 4 wire Q 100Q with offset compensation on With offset compensation on OPEN CKT VOLTAGE is 12 8V For 2 wire Q add 1Q additional uncertainty 7 Must have 10 matching of lead resistance in Input HI and LO Test current 0 74 A 10MQ Add th
43. I Press SHIFT press MATH select the low ohms cal CALC1 STAT ON SIIOHMS culation Close channels to ROUT MULT CLOS Press CLOSE select MULTI select test bridgewire 101 102 117 101 gt select 102 gt select 117 gt select 118 124 121 118 gt select 124 gt select 121 gt press EXIT Verify channels ROUT MULT CLOS Press SHIFT gt press CARD gt select that are closed VIEW gt select SLOT1 7751 7752 or optional 7753 Press EXIT when finished 6 Perform measure READ Take reading from display ment 7 Open all channels ROUT OPEN ALL Press OPEN gt select ALL Test step notes 1 Resetting the 2790 opens all channels selects the DCV function auto range and selects the I source of the 7751 7752 7753 mod ule For remote programming RST places the 2790 in the one shot trigger mode For front panel operation FACT defaults places the 2790 in the continuous trigger mode 2 This step sets the I source to output ImA Do not use a higher test current for this dry circuit test For front panel operation and a 7751 7753 module the V source output setting will be displayed after setting the I source output 3 This step selects the low resistance calculation R VygAs Isour Selecting SIIOHMS sets DMM to DCV 1V range 4 This step closes the channels to make the test connections for the shunt bar test It assumes shunt bar is connected to Bank 1 of a 7751 7752 or 7753 Channel 124 is closed
44. Iohms or SxVo hms is selected using the FORMat command No further actions are required by the user CALCulate 1 KMATh MMFactor TRACk b Enable or disable source tracking CALCulate 1 KMATh MMFactor TRACK Query state of source tracking CALCulate 1 KMATh MMEFactor SOURce lt name gt Selects source to be tracked NONE SIISource SI VSource S21Source S2VSource CALCulate 1 XMATh MMFactor SOURce Query source to be tracked l Selecting an ohms calculation enables source tracking Selecting any other math function disables source tracking Programming errors 222 Parameter out of range Attempted to select a source SOURCe command with a 7702 card installed 241 Hardware missing Attempted to select a source SOURCe command that is not installed 870 Invalid current error Attempted to track an I source that is set to OmA For the low ohms calculation m 1 Iggyg Dividing 1 by 0 would result in an erroneous reading positive infinity Model 2790 SourceMeter Switch System User s Manual 2 13 Opening and closing channels Multiple channel operations are used to control 7751 7752 and 7753 channels e Only the specified channels are opened or closed Unspecified channels are not affected e Relays to connect signals to the backplane DMM of the Model 2790 do not close automatically You must explicitly close them to perform a measurement For example with a DUT connected to ch
45. L is displayed for a slot 1 violation and IL2 is displayed for a slot 2 violation In the case of errors for both slots the IL1 message takes precedence Overflowed readings stored in the buffer do not provide interlock status You cannot tell if the overflow readings are true overflows or the result of open interlock see Remote programming errors below Remote programming errors When an open interlock is first detected error 860 slot 1 interlock violation or 861 slot 2 interlock violation occurs The questionable event register in the status byte can be read to determine which interlock tripped see Section 11 of the Model 2790 Reference Manual The firmware polls for interlock violations every 50msec To avoid filling up the error queue once an error is issued for a given interlock it must be reset interlock enabled before another error event will be issued to the status model for the same interlock Error 224 parameter error occurs if you attempt to close channel 18 19 or 21 with interlock open With interlock open channel 20 will close and remain closed while interlock is open ROUT OPEN ALL will open all channels except channel 20 ROUT MULT OPEN will generate error 224 parameter error Model 2790 SourceMeter Switch System User s Manual 2 17 Cable discharge circuit 7751 and 7753 Leakage capacitance exists between signal paths on the switching module and in the test cables This capacitance can be
46. OTx Slot1 or Slot2 101 145 Select module Shows channels 101 and 145 closed Closed channels scrolled Model 2790 SourceMeter Switch System User s Manual 3 13 Using 7751 7753 V source with 7702 module WARNING The 7702 module is designed to handle DC peak voltages up to 300V generated by external and potentially unlimited energy type sources When the 7702 module is used in conjunction with the 7751 7753 mod ule it can be used safely up to the full output voltage capability of the 7751 7753 V source 500V DC peak This DOES NOT imply that the 7702 module can be used with EXTERNAL SOURCES i e non 7751 7753 derived above 300V DC peak NOTE Although the 7702 module is rated for 300V it can be used with the 500V output from the 7751 7755 module due to the extremely low current available from the source No safety or reliability issues will result from using the 7751 7753 out put with the 7702 module if the equipment is used according to the instructions provided The V source of the Model 7751 7753 can be used with the 7702 module A typical test system is to use the Model 7702 as a dual multiplexer to bias and measure up to 20 DUTs The V source of 7751 7753 module powers the DUT while the DMM of the Model 2790 measures the output of the DUT To prevent overloading of the V source each DUT is powered and measured separately Figure 3 10 shows the test circuit for this application The 7751 V source is conn
47. SEN A4 B4 HI HI LO LO SRC SEN SRC SEN A3 B3 x I m ee e e ee ee 00000 0229097 See eee m mmm mmm o om omo a m u m m m m mm mm mm mm mm A Model 2790 SourceMeter Switch System User s Manual 4 6 Figure 4 3 Model 7702 screw terminal channel designations CH4 CH6 CH8 CH10 CH12 CH14 CH16 HL HL HL HL HL H L H L CH18 CH5 CH7 CH9 CH11 CH13 CH15 CH17 HL CH3 H L H L H L H L H L H L H L H L CH19 H L CH2 HL CH20 HL CH1 HL M TE122 zane EHI 0p ee e ze TE121 e mu CIDODD isa HL CH21 H L H L CH40 CH22 T HL HL HL HL HL CH26 HL CH23 HL HL HL HL H L H L H L CH25 CH27 CH29 CH31 CH33 CH35 CH37 INPUT SENSE H L HL zm 00 Model 2790 SourceMeter Switch System User s Manual 4 7 Figure 4 4 Wire dressing 7751 7752 7753 mmm UJ mom mom mom mom m Hm m mim m pores Supplementary s 17 Insulation SOURCE SENSE g j 1 ye D 1 GUARD HI LO HI LO j See OO OGD OY SS O O O 0 0 0 0 0 OOOO 9 9 OO SRC SEN SRC SEN A B HI HI LO LO
48. V source output setting not published in the specification sheet Ohms accuracy and temperature coefficient are specified as percent of reading plus an ohms offset 7751 7752 7753 l source Low ohms specifications using the I source of the 7751 7752 7753 are provided for the following current output settings 50mA 20mA 10mA and 1 mA dry circuit ohms Use the following formulas for other I source settings NOTE The following formulas are only valid when using IVDC range of the Model 2790 DMM When using the SIxOhms math calculation the 1V range is selected automatically Ohms accuracy do of reading 0 07 l IgoURCE Ohms offset 0 03 IsourcE where Isougce is the current output setting in mA Example Determine ohms accuracy for an I source setting of 30mA of reading 0 07 1 30 0 07 0 03 0 10 Ohms offset 0 03 30 Q mQ Ohms accuracy 30mA 0 10 1mQ Model 2790 SourceMeter Switch System User s Manual Specifications A 9 Ohms temperature coefficient TC of reading 0 001 0 025 IggurcE C TC ohms offset 0 001 ISOURCE Q C where Isource i the current output setting in mA Example Determine temperature coefficient for an I source setting of 30mA of reading 0 001 0 025 30 C 0 001 0 00083 0 00183 C Ohms offset 0 001 30 Q C 0 033mQ C Ohms temperature coefficient 30mA 0 00183 0 033m 2 C 775
49. al Figure 2 1 Simplified schematic of Keithley 7751 7752 and 7753 switching modules Source 0 0 C HI Ch 1 Sense Source 0 0 O LO Ch 2 Sense A1 ae Ch 3 1 Source 0O O C HI Ch 4 Sense Source 0 0 O LO Ch 5 Sense Bank 1 J101 Bank 2 J102 Bank 3 J103 Bank 4 J104 Vsource Ch 28 751 7753 50 500V qx Only A2 o oe Ch 6 B2 p Source HI Ch 7 Sense Source 0 0 C LO Ch 8 Sense Source 0 0 C HI Ch 10 Sense Source 0 0 O LO Ch 11 Sense Ch 12 B4 Isource Ch 27 l0 50mA Ch 25 o Ch 13 O TI ew o LL l BE Ch 15 Q O 0 0o HI Ch 16 paint O To Model 2790 o o o HI Backplane ch 17 1 Sense IT apg Source Enable O Pid 5V J106 F Interlock 10kQ Guard Guard O Source HI M J105 O Source LO t O Sense HI II O Sense LO O I V IN O I V OUT J108 oO I V LO O Vsrc HI O Vsrc LO O Isrc HI J107 O Isrc LO EHE O Guard O Guard Ill 200kQ 7751 ETSI 20kQ 7753 vv Current Voltage Amplifier 7751 7753 Only zl Cable Discharge E 100kO 7751 7753 Only ch 22 Open I source Select Ch 22 Close V source Select 2 4 Model 2790 SourceMeter Switch System User s Manual I source channels 21 22 24 and 27 The programmable I source 0 to 50mA is used as the test curr
50. al Figure 2 4 Opening and closing channels A Opening one or all channels OPEN CLOSE Press OPEN key Display MULT option Display ALL option and press ENTER and press OPEN again OPEN MULT OPEN MULT XXX OPEN ALL Display channel number XXX and press ENTER B Closing a channel Press CLOSE key Display MULT option and press ENTER CLOSE MULT Specify channel number CLOSE MULT XXX XXX and press ENTER Remote programming The commands to control 7751 7752 and 7753 channels are listed in Table 2 3 Table 2 3 Commands to control 7751 7752 7753 module channels ROUTe MULTiple CLOSe lt clist gt Specify one or more channels to close ROUTe MULTiple OPEN lt clist gt Open channels specified in list Unlisted channels not affected ROUTe OPEN ALL Open all channels ROUTe MULTiple CLOSe Returns a lt clist gt of all closed channels ROUTe MULTiple CLOSe STATe lt clist gt Query closed channels in specified list 0 open 1 closed ROUT OPEN ALL will open all channels except channel 20 if interlock is open Examples ROUT OPEN ALL Open all channels ROUT MULT CLOS 101 114 118 Close channels for slot 1 ROUT MULT CLOS Return list of closed channels Model 2790 SourceMeter Switch System User s Manual 2 15 Viewing closed channels Closed channels can be viewed from the VIEW item of the CARD menu The menu struc ture is accessed by pressing and re
51. and or insulated from every connection point In some cases connections must be exposed to potential human contact Product operators 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 Do not connect switching cards directly to unlimited power circuits They are intended to be used with impedance limited sourc es NEVER connect switching cards directly to AC mains When connecting sources to switching cards install protective de vices to limit fault current and voltage to the card Before operating an instrument make sure the line cord is connected to a properly grounded power receptacle Inspect the con necting cables test leads and jumpers for possible wear cracks or breaks before each use When installing equipment where access to the main power cord is restricted such as rack mounting a separate main input pow er disconnect device must be provided in close proximity to the equipment and within easy reach of the operator 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 ca 5 03 bles or jumpers installing or removing switching cards or making internal changes such as installing or rem
52. ank 4 Sense J104 Source L o oo O Ch 11 Sense lt S 3 p a e 3 gt p C 5 z NP EN O Q O AAA 5 Ch 28 50 500V 7751 7753 Only Isource 20mV Q Ch 27 Dry O Ck Ch 22 Ch 22 Open Isource Select Ch 22 Close Vsource Select To Model 2790 Backplane Source Enable Interlock 5V t 5V J106 Interlock 10K Guard Guard Source HI me Source LO Sense HI Sense LO I V OUT J108 I LO Vsrc HI Vsrc LO Isrc HI War Isrc LO 10K Guard V O Guard 200K 7751 20K 7753 I V Current Voltage Amplifier 7751 7753 Only Q 1 Q 100KQ O O Ch 20 Cable Discharge 7751 7753 Only HW 11 04 03 Rev D 2790 SourceMeter Switch System Specifications 2790 MAINFRAME FUNCTION SPECIFICATION MAINFRAME FUNCTION ACCURACY SPECIFICATIONS ARE FOR 1 YEAR 23 C 5 C DC MEASUREMENT SPECIFICATIONS CONDITIONS MED 1 PLC or 10 PLC or MED 1 PLC with Digital Filter of 10 Function Voltage Resistance Continuity 2W Current Channel Ratio Temperature Range 100 0000 mV 1 000000 V 10 00000 V 100 0000 V 1000 000 V 100 0000 Q 1 000000 KQ 10 00000 KQ 100 0000 KQ 1 000000 MQ 10 00000 MQ 100 0000 MQ 1 000 KQ 20 00000 mA 100 0000 mA 1 000000 A 3 000000 A Test Current 45 Resolution or Burden Voltage 0 1 uV 1 0 uV 10 pV 100 uV mV 100 uQ mA mQ mA 10 mQ 100 pA 100 mQ 10 pA
53. annel 1 of a 7751 7752 or 7753 module you would have to close channels 1 14 and 18 to measure it with the Model 2790 Closed channels are not displayed by the Model 2790 while in the normal display state Closed channels can be viewed from the VIEW item of the CARD menu see Viewing closed channels for details To control the appropriate switching module the slot number must be included with the switching module channel number The channel assignment is formatted as follows SCH where Sis the slot number 1 or 2 CH is the channel number Examples 101 Slot 1 Channel 1 218 Slot 2 Channel 18 NOTE Interlock of the 7751 7752 7753 must be enabled in order to close channel 16 19 or 21 and open channel 20 See Open interlock errors for errors associ ated with open interlock and see Interlock in Section 5 for details on using the interlock Front panel operation As shown in Figure 2 4 the OPEN and CLOSE keys are used to control 7751 7752 and 7153 channels After closing or opening a single channel e A message indicating the action i e 101 CLOSED will be displayed briefly e To close another channel simply key in the channel number and press ENTER e Press EXIT to exit from the open close menu structure NOTE The edit keys left right up and down arrow keys are used to display a channel number Pressing ENTER opens or closes the channel 2 14 Model 2790 SourceMeter Switch System User s Manu
54. asurements gt 1GQ it is recommended that the DUT be con nected between two different banks for example Bank I and Bank 3 as seen in test connection figures to reduce the possibility of measurement errors caused by leakage resistance 5 24 Model 2790 SourceMeter Switch System User s Manual HIPOT test This test is used to measure the leakage resistance between an initiator bridgewire and the housing Single stage inflator connections to the 7751 7753 module is shown in Figure 5 3 while dual stage inflator connections are shown in Figure 5 5 NOTE The interlock of the 7751 7753 must be enabled in order to use the V source Figure 5 6 shows how interlock is enabled Test circuit The circuit for the HIPOT test is shown in Figure 5 12 Internal shunts The HIPOT test is usually performed with the shunt bar installed This shorts the bridgewire to prevent accidental ignition of the inflator However if the short bar is not installed or should it become defective the protection is gone Therefore the 7751 7752 and 7753 provide built in shunts They can be used in lieu of or with the shunt bars to provide additional safety As shown in Figure 5 12 closing channel 3 or 6 connects the internal shunt across the bridgewire Single stage inflator Closing input channel 1 connects the first bridgewire Dual stage inflator Closing input channel 4 connects the second bridgewire Model 2790 SourceMeter Switch Syste
55. ations J101 Input channels 1 3 J102 Input channels 4 6 BANK 1 NE BANK 2 SRC SEN SRC SEN Ai Bi SRC SEN SRC SEN A2 B2 HI HI LO LO HI HI LO LO J105 E SOURCE SENSE E N um oum oum oum ew ee ee ee umo ee eB umo umo umo ee eB moo eB moo GUARD HI LO HI LO BANK 1 SOURCE SENSE SRC SENNSRC SEN Al B1 GUARD HI LO HI LO HI HI XO LO Asia n n ads ans ni Ru RE md ma c uw s mad n fn nd Uni ind nn ee es BANHKJ2 QO YY QD Y O SRC SEN SRC SEN A2 ge Hi HI LO o COO O O O O Q O O O0 0 eS A A SS OO QS SS PY eee 5 om o eee ee ee eee eee 99 J106 i i g 7 2 LL y y TTT DOBRO O U i O OO Q O Q Ox O Q O O O O O O_O OO PS io DDOD DIDO X V U D UA UD ADODO D sre sen src dn a ea INT 5V INT LO HI LO IN OUT LO HI HI O LO BARRY I INTERLOCK VSOURCE ISOURCE GUAB I V SRC SE SRC SEN A3 B3 INT 5V INT TS INTERLOCK i a _ Se a ee d J103 Input channels 7 9 J104 Input channels 10 12 a sees eee eee eee Be ee Be Be eB Be Be Be Be EB ARQ HI LO HI LO VSOURCE ISOURCE GUARD I I UU E RE RII EMG EBR2 5 lI EE T a E E FERRE 2 E 0 35 HI HI LO LO SRC SEN SRC
56. ay to O Enable reading Select 2 wire ohms Select 100 range Select 1 PLC Set channels 4 14 and 18 for memory location 2 Set delay to O Enable reading Select 2 wire ohms Select 100 range Select 1 PLC Model 2790 SourceMeter Switch System User s Manual Table 5 7 cont Command sequence for memory patterns test example using scanning Set up memory location 3 ROUT MEM CHAN 3 108 115 118 ROUT MEM DEL 3 0 SENS FUNC RES M3 SENS RES RANG 100 M3 SENS RES NPLC 1 M3 ROUT MEM READ STAT 3 ON Set up to scan trigger scan store readings ROUT SCAN M1 M2 M3 TRIG SOUR IMM TRIG COUN 1 SAMP COUN 3 TRAC CLE TRAC POIN 3 TRAC FEED CONT NEXT ROUT SCAN LSEL INT INIT Wait for scan to complete before continuing ROUT SCAN LSEL NONE TRAC FEED CONT NEVER ROUT OPEN ALL FORM ELEM READ TRAC DATA Set channels 8 15 and 18 for memory location 3 Set delay to 0 Select 2 wire ohms Select 100Q range Select 1 PLC Enable reading Set up scan for three memory locations Immediate trigger source Trigger count 1 Sample count 3 Clear buffer Store three readings in buffer Enable buffer Enable scan Trigger scan Disable scan Disable buffer Open all relays Send readings only from buffer Request all buffer readings Model 2790 SourceMeter Switch System User s Manual Table 5 8 5 33 Command sequence for memory
57. be used for HIPOT testing while the I source of the second module 7752 can be used to test other non inflator type circuitry 1 e pushbutton switches and resistors on the steering wheel The I source allows accurate resistance measurements up to 100 2 2790 L configuration one 7752 module This test system includes a single 7752 module It is applicable for testing that does not require high voltage HIPOT testing but still needs the programmable I source for low ohms testing Insulation resistance up to 120M Q2 can be measured using the 22 function of the Model 2790 2790 H L A 7702 configuration one 7751 7752 7753 one 7702 module This test system includes a 7751 7752 or 7753 module and a 7702 module The 7702 module can be used for non inflator related ohms testing that requires 20 40 channels of 4 wire 2 wire measurements Typical tests using the 7702 module include burn in life QA testing of multi pin connectors wiring harnesses power distribution fuse centers switches and relays and backplanes Model 2790 SourceMeter Switch System User s Manual 1 5 2790 A configuration one 7753 module This test system includes a single 7753 module This module has a programmable 50 to 500V V source and I V amplifier for HIPOT testing It also has a programmable 0 to 50mA constant current I source to measure the resistance of shunt bars and bridgewires Supplementary system components For added versatility or as spares
58. bridgewire is connected to Bank 2 of a 7751 7752 or 7753 9 This step is optional Use it to verify that the correct channels are closed for the test 10 For remote programming READ triggers and requests a single reading 11 Always open all channels at the beginning and end of a test EN oO 1 ON tA I source readback The 7751 7752 and 7753 modules have source readback capabilities I source readback allows you to verify the test current used in the bridgewire test Details on I source read back are provided in the last topic in this section Model 2790 SourceMeter Switch System User s Manual 5 17 Insulation resistance HIPOT tests 7751 7753 only WARNING The Models 7751 and 7753 are provided with outputs that are poten tially hazardous if not connected properly It is the responsibility of the customer to operate instruments in a safe manner Be sure to read and follow all installation and operating instructions before attempting to use the 7751 7753 HIPOT function There are three basic tests for insulation resistance Two preliminary verification tests and the HIPOT test e Contact checks These checks use the ohmmeter of the Model 2790 to verify that the V source test circuit is properly connected to the inflator housing and the bridgewire e V source readback This test uses the voltmeter of the Model 2790 to measure the actual output of the V source This test should be done before every HIPOT test
59. control 7702 module channels 3 11 Inflator Testing Test procedure shunt bar cccccccssssssssssesssssseessseesseeeees 5 13 Test procedure Dridgewire adossscssumisiEessekess elouetusdevlodtocuduus 5 15 Test procedure contact checks for single stage inflator 5 20 Test procedure contact checks for dual stage inflator 5 21 Test procedure V source readback 5 23 Test procedure HIPOT asus oieistniettmbecssebUsibGou baau dul utes dou 5 26 Command sequence for memory patterns test example UTE SCOTI A E E dedu LIIS uu Us tists ugue LIO accra 5 31 Command sequence for memory patterns test example using individual memory pattern recall 5 33 Model 2790 DMM Ohms Functions Commands to set offset compensated ohms 6 5 1 Test System Overview Introduction Summarizes the switching modules that are used with the Model 2790 to test inflators Covers some key features of the Model 2790 and defines explains technical terms associated with airbag inflators Model 2790 configurations Explains the various mainframe module combina tions available from Keithley Test system Shows a typical test system used to test inflators Inflator tests Explains the three basic tests for inflators shunt bar bridgewire and insulation resistance HIPOT Introduction Model 2790 SourceMeter
60. covered in Section 4 Details on using the Keithley 7702 module are provided in the Model 2790 Reference Manual Details on using the ohms functions of the Model 2790 with the 7702 module are provided in Section 6 The edit keys left right up and down arrow keys are used to display menu items and output levels With the desired menu item or output level displayed it is selected by pressing ENTER For remote programming the lt clist gt parameter is used as follows lt clist gt SCH where S Mainframe slot number 1 or 2 CH Switching module channel number of source 2 digits Examples 201 Slot 2 Channel I 201 214 218 Slot 2 Channels 1 14 and 16 5201 210 Slot 2 Channels 1 through 10 Safety precautions In a system to test inflators a 7702 module may be used with the 7751 7752 or 7753 module In a mixed module configuration like this the following safety precautions must be understood and taken External energy sources should never be applied directly to a 7751 7752 or 7753 module for any reason Damage to the module and any connected devices under test can result due to the application of improperly selected or performing external energy sources Additional precautions should be taken when using the mainframe measurement functions for the 7751 7752 7753 modules and an external source connected through the Model 7702 switch module In the case of a single hardware or software configurat
61. d end of a test NOTE To use the DMM of the Model 2790 to measure a DUT connected to a switching module the front panel INPUTS switch must be in the REAR in position Test system Figure 5 1 shows a typical test system and connections using a programmable logic con troller PLC or a PC Connections for the test signals and interlock are covered in Test signal connections NOTE Only one Model 7753 can be installed in a Model 2790 and it should be installed in slot 1 A 7753 module can be used in slot 2 but measurement accuracy might be adversely affected because cards are always calibrated in slot 1 Figure 5 1 System connections i 3 DB 9 Cable Device Handler RS 232 Cable Mechanical Test Signal C t DB 9 4 Keithley 2790 Cabling Keith an 7751 7752 or B Test Station T j F OR oo 2 790000 2 7753 Module B with Interlock ll Interlock R Inflator Under Test DIGITAL I O poo System Interlock KPCI 488 GPIB Cable r Expansion Interface IEEE 488 M Cable 7008 3 008 6 When using a PLC select and configure the RS 232 interface of the 2790 If using a PC select the GPIB interface and set the address of the 2790 Use a cable terminated with a female DB 9 connector to mate to the DIGITAL I O connector of the 2790 Cable must be wired as a straight through cable not null modem cable BRWN Model 2790 SourceMeter Switch System User s Manual RS 232
62. d external cir cuitry The Models 7751 7752 and 7753 use quick disconnect terminal blocks A terminal block can be wired outside the module and then plugged back in Figure 4 1 shows how to access the screw terminals on the switching module Channel designations for the screw terminals are contained in Figure 4 2 7751 7752 7753 and Figure 4 3 7702 Model 2790 SourceMeter Switch System User s Manual 4 3 CAUTION For the Model 7751 7753 be sure that the thermal pad is not dislodged Also be sure to use the correct cover with the integral heat sink to assure proper voltage source operation Note that earlier 7751 modules do not have the pad or heat sink Figure 4 1 Screw terminal access Heat Sink Underneath Conductive Thermal Pad LOCK EANCT 99939S 3 9999393 TIS T 9 0 0 O O O O0 O O O O O 000000 LLL 3 5c 8 5 a 2 o 2 2 52 9 So oo oO i200 2020002090 0000QQQ s m s Cabling requirements General requirements Cable wires should be mechanically durable preferably 20AWG or larger with a high voltage insulation such as rubber or silicon good for at least 1000V It is the responsibi
63. d personal contact with these voltages The A symbol indicates a connection terminal to the equipment frame The WARNING heading in a manual explains dangers that might result in personal injury or death Always read the associated information 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 war ranty Instrumentation and accessories shall 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 Instruments Standard fuses with applicable national safety ap provals may be used 1f 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 selected 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 not apply cleaner directly to the instrument or allow liquids to enter
64. e 50V to 500V CH 28 Programming Resolution 100mV Output Current 7751 50uA maximum for rated accuracy 1mA typical into short circuit 7753 500LA maximum for rated accuracy 1mA typical into short circuit Accuracy 0 5 0 13V 2yr Specification Settling Time Rise Time 50V to 500V step 0 1 of final value 250 ms max Fall Time 500V to 50V step 0 196 of final value 1000 ms max Temperature Coefficient 0 18 C amp 28 40 C 0 001 0 005V C Safety Limit Current limited maximum current of 1 mA Cable Discharge Ch 20 100kQ Shunt Max Capacitance 1nF Current Measure Input 7751 7753 Only Range 7751 0 504A 7753 0 500uA Accuracy 7751 0 5 of reading 6nA 2yr Specification 7753 0 5 of reading 60nA 2yr Specification Temperature Coefficient 0 18 C amp 28 40 C 0 02 0 5nA C Voltage Burden 1mV Switching Capabilities Bank 1 Bank 4 4 Channels Form A switch 8 Channels 4 4 pole or 8 2 pole signals into DMM or I V converter Contact Check 4 Wire contact check through internal DMM Relay Type Latching electromechanical Actuation Time lt 3ms Contact Life typ gt 10 operations at maximum source level gt 10 operations cold switching lt 1 Ohm at end of contact life lt 2uV typical per contact pair x34 V max Contact Resistance Contact Potential Connector Type Plugable screw terminal 22 AWG wire size Isolation Bet
65. e following to ppm of reading uncertainty when using plug in modules 10MQ 100MOQO 220 ppm 2200 ppm 10 KQ 100kQO 1 MQ 7702 7751 7752 Add 1V when used with plug in modules For RATIO DCV only For AVERAGE DCV only Available with plug in modules only l Auto zero off For LSYNC On line frequency 40 1 For LSYNC Off use 60dB for gt IPLC P For 1kQ unbalance in LO lead Speeds are for 60Hz 50Hz operation using factory defaults operating conditions RST Autorange off Display off Limits off Trigger delay 0 P Speeds include measurements and binary data transfer out the GPIB 1 Sample count 1024 auto zero off 17 Auto zero off NPLC 0 01 55 For lead resistance gt 0Q add the following uncertainty Q for measurement temperatures of 70 100 C 100 150 C 2 2kQ 44004 022 C 1 11 C 5 0 kQ 44007 0 10 C 0 46 C 10kQ 44006 0 04 C 0 19 C HW 11 04 03 Rev D 2790 SourceMeter Switch System Specifications MAINFRAME FUNCTION SPECIFICATION AC MEASUREMENT SPECIFICATIONS All Ranges Accuracy of reading of range 23 C 5 C All Ranges 3 Hz 10 Hz 20 kHz S0 kHz 100 kHz Function Range Resolution Calibration Cycle 10 Hz 20 kHz S0 kHz 100 kHz 300 kHz Voltage 100 0000 mV 0 1 uV 90 Days 0 35 0 03 0 05 0 03 0 11 0 05 0 6 0 08 4 0 0 5 1 000000 V 1 0 pV 10 00000 V 10 uV 1 Year 0 35 0 03 0 06 0 03 0 12 0 05 0 6 0 08 4 0 0 5 100 0000 V 100
66. e instruments in a safe manner Be sure to read and follow all installation and operating instructions before attempting to use the 7751 7753 HIPOT function The leakage resistance Ryrpor between each of the initiators and the housing must be verified As shown in Figure 1 4 this is performed by applying a voltage typically 500V between the bridgewire and the housing The resultant test circuit current is applied to an I V amplifier where it is converted to a voltage This voltage is then measured by the DMM of the Model 2790 NOTE lfnot using a 7751 7753 module in your test system resistance up to 120MQ can be measured using the Q2 function of the Model 2790 Figure 1 4 HIPOT testing 7751 7753 RHIPOT 1 I V Amplifier 7751 7753 lteteenseeeaseeeneseeed E VSOUR x Re Re 200kQ 7751 V MEAS Re 20kQ 7753 Model 2790 SourceMeter Switch System User s Manual With the high ohms math function Sx Vohms selected the Ryrpor reading can be read directly from the display of the Model 2790 Before measuring Ryyporz there are a couple of preliminary verification tests that should be performed first e Contact checks To properly perform the HIPOT test contact must be made to the air bag inflator housing If good contact is not established the measured high resistance will not represent the isolation resistance Contact is checked by per forming continuity checks through the V source test leads and the conn
67. e layers which could give a false indication of the shunt resistance Dry circuit conditions require that the voltage applied to the DUT be limited to 20mV or less Closing channel 24 of the 7751 7752 7753 module enables the 20mV dry circuit clamp Model 2790 SourceMeter Switch System User s Manual 5 11 When using the dry circuit test current is automatically limited to slightly more than ImA regardless of the programmed level Therefore it is recommended that the I source output be set to ImA or less to ensure that a known current is being used for the resistance measurement NOTE The Sxlohms math functions use the programmed I source values for their cal culations If the I source output is not set to ImA or less while dry circuit is enabled channel 24 closed these math functions will give incorrect resistance readings NOTE Typically the shunt bar test is usually the first step in the testing process for an inflator The typical test station uses a spring loaded mechanism that automati cally installs or removes the shunt bar Test circuit The circuit for the shunt bar test is shown in Figure 5 7 Note that the 20mV dry circuit clamp is used for this test Ch 22 open I source selected Figure 5 7 Test circuit shunt bar Keithley 7751 7752 or 7753 ams VMEAS Ma LLL LLL1ll l LIO 1lelA h1hJQQ QM ISOUR 21 1Q 1 or 4 Lor 4 17 18 Input HI Shunt Bar SOURCE i Under 2
68. eading should be 2 2 or less Open all channels ROUT OPEN ALL Press OPEN select ALL Test step notes Resetting the 2790 opens all channels and selects the DCV function auto range For remote programming RST places the 27790 in the one shot trigger mode For front panel operation FACT defaults places the 2790 in the continuous trigger mode This step selects the 22 measurement function of the Model 2790 This step closes the channels to make the connections for the HI contact test bridgewire A This step is optional Use it to verify that the correct channels are closed for the test For remote programming READ triggers and requests a single reading Always open all channels at the beginning and end of a test This step closes the channels to make the connections for the HI contact test bridgewire B This step is optional Use it to verify that the correct channels are closed for the test 9 For remote programming READ triggers and requests a single reading 10 Always open all channels at the beginning and end of a test 11 This step closes the channels to make the connections for the housing contact test 12 This step is optional Use it to verify that the correct channels are closed for the test 13 For remote programming READ triggers and requests a single reading 14 Always open all channels at the beginning and end of a test oo 1090 tA BW WD 5 22 Model 2790 SourceMeter Switch System User
69. ected to the Sense terminals of the 7702 module DUTS are connected to channels 1 through 20 of the 7751 7753 module Channels 21 through 40 are used to connect the V source to each DUT To use the 7702 module as a dual multiplexer multiple channel operation must be used to control channels for this application All channels of the 7751 7753 module are to remain open NOTE Section 2 Setting source output levels explains how to set the output of the V source of the 7751 7753 module During the testing process channels 43 and 45 of the 7702 are to remain closed To test DUT 1 input channels 1 and 21 are then closed To test DUT 2 input channels 2 and 22 are closed DUT 3 through 20 are tested in a similar manner by closing the appropriate pair of input channels Keep in mind that when testing a DUT only the two appropriate inputs are closed All other input channels must be open NOTE See Multiple channel operation Dual independent multiplexers in Section 2 of the Model 2790 Reference Manual for details on using the 7702 module as a dual multiplexer In Figure 2 9 of the reference manual the 7751 7753 V source would replace the External Source Model 2790 SourceMeter Switch System User s Manual Figure 3 10 Using 7751 7753 V source with 7702 module dual multiplexer All 7751 7753 channels open e VSOURCE O ar Closed channel T M O Open channel Note Shown are 7702 channels 1 21 43 and 45 c
70. ection points The resistance reading for a contact should be less than 20 ohms depending on cabling e V source readback Before performing the HIPOT test the output voltage of the V source should be verified The V source readback circuit allows you to directly measure the output voltage using the DMM of the Model 2790 2 Keithley 7751 7752 and 7753 Switching Modules Card configuration Provides the simplified schematic of the Keithley 7751 7752 and 7753 switching modules Summarizes the individual components of the modules e Setting source output levels Explains how to set the output levels for the I source 7751 7752 7153 and V source 7751 7753 e Math Covers the ohms math functions used to calculate low resistance when using the I source of the 7751 7752 7753 and high resistance when using the V source and I V amplifier of the 7751 7753 module Opening and closing channels Explains how to open and close channels for the 7751 7752 and 7753 modules e Viewing closed channels Explains how to display closed channels on the Model 2790 e Open interlock errors Explains the errors associated with an open interlock e Cable discharge circuit 7751 and 7753 Explains the cable discharge circuit It dissipates voltage at the input channels This unwanted voltage could ignite the inflator e Connection log Use to record connection information e Using memory patterns Describes
71. ed before using this product and any associated instrumentation Although some instruments and accessories would normally be used with non hazardous voltages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury Read and follow all installation operation and maintenance information carefully before using the product Refer to the manual for complete product specifications If the product is used in a manner not specified the protection provided by the product may be impaired The types of product users are Responsible body is the individual or group responsible for the use and maintenance of equipment for ensuring that the equip ment is operated within its specifications and operating limits and for ensuring 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 instrument 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 properly for example setting the line voltage or replacing consumable materials Maintenance procedures are described in the manual The procedures explicitly state if the operator may perform them Otherwise they should be
72. ed to Bank 1 3 Closed channel switch Channels 4 and 5 closed for applications with two shunt bars 5 30 Model 2790 SourceMeter Switch System User s Manual Memory patterns test As discussed in Section 2 Model 2790 units equipped with firmware revision A04 and higher have the capability of using memory patterns to simplify repetitive test procedures The discussion below shows how to use memory patterns to make contact checks on a dual stage inflator NOTE See Section 2 of the Model 2790 Reference Manual for a more detailed memory patterns example Test circuit As shown in Figure 5 14 there are four contact connection points for the V source test cir cuits Contact checks are performed as follows e Bank 1 HI contact Close channels 1 14 and 18 to check the connection at the HI terminal of bridgewire A e Bank 2 housing contact Close channels 8 15 and 18 to check the connection at the housing of the inflator e Bank 3 HI contact Close channels 4 14 and 18 to check the connection at the HI terminal of bridgewire B Figure 5 14 Test circuits memory patterns dual stage inflator contact test 2790 DMM Contact Point 2790 1 of 3 EM Dual Stage Inflator 9 Closed channel switch NOTE Each channel is a 2 pole Test assumptions switch Therefore when a Inflator housing connected to Bank 3 channel is closed two Bridgewire A connected to Bank 1 switches close see Bridgewire B connected
73. el Average the chan nels are paired as follows e CHlandCH21 CH6 and CH26 e CH11 and CH31 CH16 and CH36 e CH2 and CH22 CH7 and CH27 e CH12 and CH32 CHI7 and CH37 e CH3 and CH23 CH8 and CH28 e CH13 and CH33 CHI8 and CH38 e CH4 and CH24 CH9 and CH29 e CH14 and CH34 CH19 and CH39 e CH5 and CH25 CH10 and CH30 CH15 and CH35 CH20 and CH40 Model 2790 SourceMeter Switch System User s Manual Figure 3 1 Simplified schematic of Keithley 7702 switching module Input LO Sense LO Ch 1 B anne i o oT 3 Channels 2 19 Channel 20 Channel 43 2 Pole Open A V A S 4 Pole Closed see Note O O UJ 2 D I e e e Q e O Q OU 3A O HI o Oo Oo Channel 42 O LO O O Channel 45 see Note Backplane Isolation O O O HI Input O O O LO Channel 44 see Note Backplane Isolation C Q O HI To Model Sense 2790 Backplane AMPS Note Channels 43 45 in this schematic refer to the designations used for control and not actual available channels Channels 43 44 and 45 can be individually controlled using multiple channel operation ROUT MULT commands if the module is not to be connected to the internal DMM Model 2790 SourceMeter Switch System User s Manual 3 5 Typical connections The following examples show typical 7702 wiring connections for the following types of measurements C22 and thermistor temperature c
74. ent to measure low resis tance inflator bridgewires and shunt bars e The I source is designated as channel 27 Opening channel 22 selects the I source Closing channel 21 connects the I source e Closing channel 24 connects the dry circuit clamp for the shunt bar test Z0mV ImA limit NOTE Ohms specification calculations in Appendix A explains how to determine the accuracy specification for source levels not specified in the 775117752 7753 Source Switch Module Specifications sheet V source and I V amplifier 7751 7753 only channels 21 22 23 28 The programmable voltage source 50 to 500V and I V amplifier are used to measure high resistance insulation resistance of an inflator The V source is designated as channel 28 Closing channel 22 selects the V source Closing channel 21 connects the V source e Closing channel 23 connects the I V amplifier WARNING Do not connect V source Hi to earth ground The 7751 7752 7753 mod ule uses a floating ground This floating ground is not connected to safety earth ground Not only will it create a shock hazard by floating up to 500V it will also effectively connect a 1nF capacitor across the V source providing energy storage that could ignite an airbag under fault conditions NOTE Ohms specification calculations in Appendix A explains how to determine the accuracy specification for source levels not specified in the 775117752 7753 Source Switch Module
75. ented in tables All test procedures assume the 7751 7752 or 7753 module is installed in slot 1 of the mainframe NOTE Only one Model 7753 can be installed in a Model 2790 and it should be installed in slot 1 A 7755 module can be used in slot 2 but measurement accuracy might be adversely affected because cards are always calibrated in slot 1 NOTE A displayed channel number on the Model 2790 is made up of the slot 1 or 2 and module channel Examples 102 Slot 1 channel 2 218 Slot 2 channel 18 Key press sequences Test procedures for front panel operation are presented as key press sequences For example the following sequence closes channel 1 for a 7751 7752 7753 installed in slot 1 Press CLOSE gt select MULTI gt select 101 gt press EXIT What the sequence means is Press CLOSE Press the CLOSE key select MULTI Use the edit keys up or down key to display the MULTI menu option and press ENTER select 101 Use the edit keys up down left or right arrow keys to display chan nel 101 and press ENTER press EXIT Press the EXIT key to exit the menu Model 2790 SourceMeter Switch System User s Manual 5 3 Closed channels for test circuits Test circuits show which channel switches need to be closed to make the test connections Keep in mind that these and only these channels must be closed for the test All other channels in the system must be open As a rule ALWAYS open all channels at the begin ning an
76. flator housing connected to Bank 3 channel is closed two Bridgewire A connected to Bank 1 switches close see schematic Bridgewire B connected to Bank 2 in Figure 2 1 5 20 Model 2790 SourceMeter Switch System User s Manual Test procedures Single stage inflator Perform the Test Steps in Table 5 3 Dual stage inflator Perform the Test Steps in Table 5 4 WARNING _ To prevent accidental detonation of the inflator ALWAYS open all channels in the test system at the beginning and end of each test Table 5 3 Test procedure contact checks for single stage inflator Test Step Command Sequence Front Panel Operation l 9 0 Reset 2790 and open all channels Select Q2 RST Press SHIFT gt press SETUP gt select RESTORE FACT Press Q2 Press CLOSE gt select MULTI gt select 101 gt select 114 gt select 118 gt press EXIT Press SHIFT gt press CARD gt select VIEW gt select SLOT1 7751 or 7753 Press EXIT when finished SENS FUNC RES ROUT MULT CLOS 101 114 118 ROUT MULT CLOS Close channels to test HI contact Verify channels that are closed optional Perform READ measurement Take reading from display Press OPEN select ALL Press CLOSE select MULTI select 108 select 115 select 118 press EXIT Open all channels ROUT OPEN ALL ROUT MULT CLOS 108 115 118 Close channels to test housing contact ROUT
77. hed when manufactured such that the open end of the cables also have shorting clips These clips are pneumatically pushed open during E check testing just after the clips resistance as a short is measured 1 4 Model 2790 SourceMeter Switch System User s Manual Model 2790 configurations Model 2790 test configurations available from Keithley include the following 2790 H configuration one 7751 module This test system includes a single 7751 module This module has a programmable 50 to 500V V source and I V amplifier for HIPOT testing It also has a programmable O to 50mA constant current I source to measure the resistance of shunt bars and bridgewires 2790 HH configuration two 7751 modules This test system includes two 7751 modules When used with a left and right type station this two module high voltage system allows higher throughput for increased efficiency e When used with a left and right type station this two module high voltage system allows two inflators to be tested It provides higher throughput for increased effi ciency When soaking is required for HIPOT testing one inflator can be tested while the other inflator is soaking high voltage applied e For a dual inflator the two high voltage module system allows parallel soak and test of each half 2790 HL configuration one 7751 and one 7752 module This test system includes a 7751 module and a 7752 module The high voltage module 7751 can
78. high enough to store a high voltage charge from the V source of the 7751 7753 module As shown in Figure 2 6 capacitance exists between the source terminals Cs and the sense terminals Cop These capacitors can be charged by the V source of the 7751 7753 module during the HIPOT test This unwanted voltage charge could ignite the inflator if it is connected to a bridgewire To prevent a high voltage charge from appearing across the inflator a discharge circuit is used As shown in Figure 2 6 channel 20 is closed to provide discharge paths through 100kQ resistors In general the discharge circuit is controlled as follows e When the interlock opens channel 20 closes to discharge the capacitors Channel 20 remains closed as long as interlock remains open see Interlock in Section 5 for details Opening channel 22 closes channel 20 for approximately 5msec to discharge the capacitors Opening channel 22 selects the I source V source disconnects from rest of module and DUT In general with the test cables connected to the module and the input channels 1 e 1 and 2 closed the following sequence should be used to properly perform cable discharge 1 Open channel 21 to disconnect the V source and I source from the input 2 Open channel 22 to perform cable discharge NOTE lf channel 22 is already open performing the MULT OPEN operation will not close channel 20 to perform cable discharge However the OPEN ALL opera tio
79. igh x 238mm wide x 370mm deep 4 125 in x 9 375 in x 14 563 in SHIPPING WEIGHT 6 5kg 14 lbs DIGITAL I O 2 inputs 1 for triggering and 1 for hardware interlock 5 outputs 4 for Reading Limits and 1 for Master Limit Outputs are TTL compatible or can sink 250mA diode clamped to 33V EARTH ISOLATION 500Vpeak gt 10GQ and lt 150pF any terminal to chassis TRIGGERING AND MEMORY Window Filter Sensitivity 0 01 0 1 1 10 or Full scale of range none Reading Hold Sensitivity 0 01 0 1 1 or 10 of reading Trigger Delay 0 to 99 hrs 1ms step size External Trigger Delay lt 2ms External Trigger Jitter lt lms Memory Size 55 000 readings MATH FUNCTIONS Rel Min Max Average Std Dev Peak to Peak of stored reading Limit Test mX b and m 1 X b with user defined units displayed REMOTE INTERFACE GPIB IEEE 488 2 and RS 232C SCPI Standard Commands for Programmable Instruments ACCESSORIES SUPPLIED User Manual and Reference Manual Screw Driver MODULES SUPPORTED Models 7751 7752 and 7702 HW 11 04 03 Rev D A 8 Specifications Model 2790 SourceMeter Switch System User s Manual Ohms specification calculations 7751 7752 7753 Ohms specifications for the 7751 7752 7753 module provide the ohms accuracy and tem perature coefficient data for specific I source and V source output values The following formulas can be used to determine the ohms specification for any valid I source or
80. iguration vientos ousups ie Di esine annene eiiie 3 3 Typical CODBEGLOBS cer oncenaic erase sdanoasmienaseoosekassusonnaxenaneonaresqusaectante 3 5 OMS er Mo MTM n 3 7 Opening and closing 7702 channels 2 rrr nenas 3 0 Channel assignments 2oieacn exito 000v vUR dU ater R2recd i cipe dt odas 3 0 Front panel operation 1 2 geudsicecusssa peso udo sia px cu nonae oap dscns 3 10 Remote programming os consis sexs tosiet sare abeundi nadatoedatuedenness 3 11 Viewing closed channelg sipsuzctasc sasuseccionademenssevuodecaverseacotaveasiiaes 3 12 Using 7751 7753 V source with 7702 module 3 13 Switching Module Wiring and Installation Connections and Wiring fruicicccatatuctantotemeeracmdinseeaniateemeiansecsienes 4 2 SCrew terminals closascnintecceddumisedetiontedsendurmeweveiuciesweuiertuadacuned 4 2 Cablmo requiTe Be DES sssrin nEs abusi eas a E ESE 4 3 Wiring procedure s oeeseseeeeeeeeretrerrerreseressssssssssnssssssssss 4 4 Zippertubing shield yovicconsrusednsausorcdasecdemagenmtasinnsimerarecrseeeust 4 8 E A RR 4 9 Switching module installation siscceciscedovesaderwwsloniielsteleseuseeuse 4 10 Module slot considerations ceccececcceeeeeceeeeeeeeeeeaeeeaaeeees 4 10 Power supply restrictions with the 7753 module 4 10 Installation procedure sos ivnsasasssvsteandscsenensdennsdetearaxnextwcsacensnes 4 10 Inflator Testing lirisgereitie Io UTENTE Om 5 2 Tsi Procedures 2 225 05 005508 90 0c305
81. in OPEN ALL Remote programming The commands to control 7702 channels are listed 1n Table 3 2 Table 3 2 Commands to control 7702 module channels ROUTe CLOSe lt clist gt Specify one input channel to close ROUTe OPEN lt clist gt Open channel specified in list ROUTe OPEN ALL Open all channels ROUTe CLOSe Return closed channel ROUTe CLOSe STATe lt clist gt Query channels in specified list 0 open 1 closed Examples ROUT OPEN ALL Open all channels ROUT CLOS 6101 Close 7702 channel 1 in slot 1 ROUT CLOS Return closed channel 3 12 Model 2790 SourceMeter Switch System User s Manual Viewing closed channels Closed channels can be viewed from the VIEW item of the CARD menu Closed channels including backplane channels and 2 pole 4 pole relay are scrolled across the display of the Model 2790 The menu structure is accessed by pressing and releasing SHIFT and then pressing CARD As shown in Figure 3 9 the closed channels will scroll across the display The four dots identify the end of the channel string Use the ENTER key to pause and resume scrolling e Press EXIT to return to the normal display state NOTE For remote programming all closed channels can be identified using ROUT MULT CLOS and ROUT MULT CLOS STAT lt clist gt See Table 2 2 in the Model 2790 Reference Manual Figure 3 9 Viewing closed channels Press Press Select SLOTx 7702 SL
82. inal channel designations 4 6 Typical connections 3 5 Viewing closed channels 3 12 Voltage connections DC or AC 3 7 Wiring procedure 4 4 Model 7751 7752 2 1 interlock 2 16 manual cable discharge 2 18 Screw terminal channel designations 4 5 Viewing closed channels 2 15 Wire dressing 4 7 Wiring procedure 4 4 Module 4 10 Multiple channels Control commands 2 8 2 12 2 14 3 11 6 5 operation 2 13 ohms math function 2 11 OPEN key 3 10 3 11 Opening and closing channels Model 7702 3 9 Model 7751 7752 2 13 operation multiple channel 2 13 Overview 1 1 oxide build up 1 7 PLC 1 5 Power 4 10 primary tests 1 6 programmable logic controller 1 5 voltage source 2 4 Programming errors 2 12 quick disconnect terminal blocks 2 5 Remote programming 2 8 2 11 errors 2 16 opening and closing channels 2 14 3 11 view closed channels 2 15 RS 232 1 5 5 4 Safety warnings 2 6 Screw terminals 4 2 Serial bus RS 232 1 5 5 4 setting 2 21 shield zipper tube 4 8 short circuit current 2 6 Shunt bar test 1 6 1 7 inflator testing 5 10 Simplified schematic Model 7702 3 4 Models 7751 and 7752 2 3 Slot numbering 2 13 3 9 Source output levels 2 6 outputs and guard terminals 2 5 readback 2 5 tracking 2 11 Specifications A 1 SxIohms 2 9 SxVohms 2 10 System connections 1 5 5 3 Test circuit shunt bar 5 11 Test configurations 1 4 Test connections shunt bar and bridgewire 5 5 shunt bar HIPOT and bridgewire 5 6 Tes
83. interface PLC or PC A PLC uses the RS 232 interface for communications with the Model 2790 A PC can also use the RS 232 Available 2790 settings for the RS 232 interface e Baud rate 19 2K 9600 4800 2400 1200 600 or 300 e Flow control XonXoff or NONE Tx terminator CR LFCR LF or CRLF The RS 232 menu of the 2790 is accessed by pressing and releasing SHIFT and then pressing RS 232 Once in the menu use the following key press sequence to select and configure the RS 232 Select RS 232 ON gt select BAUD rate gt select FLOW control gt select Tx TER Minator GPIB PC only The GPIB which is faster than RS 232 can be used if an IEEE 488 Interface card e g KPCI 488 is installed in the computer The GPIB menu of the Model 2790 is accessed by pressing and releasing SHIFT and then pressing GPIB Once in the menu use the following key press sequence Select GPIB ON gt select ADDRess address 16 is set at factory Model 2790 SourceMeter Switch System User s Manual 5 5 Test signal connections There are four main test connection drawings Figures 5 2 5 3 5 4 and 5 5 but you only need to use the one that applies to your test system Select the drawing that best suits your needs and disregard the other three NOTE All the test circuits and procedures in this section assume that the inflator is con nected to the 7751 7752 7753 module as shown in Figure 5 2 through Figure 5 5 Single stage inflator test co
84. ion error or in a fault condition external energy sources can become directly connected to unintended device under test connections Where this possibil ity exists it is the system designer builder s sole responsibility to ensure under all such fault conditions that no hazardous or damaging situations are created Model 2790 SourceMeter Switch System User s Manual 3 3 Card configuration Unlike the 7751 7752 and 7753 modules the 7702 module supports system channel operation That is when an input channel is closed other channels on the module automat ically close to connect the input to the backplane DMM of the Model 2790 Figure 3 1 is a simplified schematic diagram of the Model 7702 module As shown the Model 7702 has channels that are grouped into two banks of twenty channels forty chan nels total Backplane isolation is provided for each bank The first bank contains channels 1 through 20 while the second bank contains channels 21 through 40 Each channel of the 40 channel multiplexer card is wired with separate inputs for HI LO providing fully iso lated inputs The Model 7702 also provides two channels of current input Channels 41 and 42 Although the Model 7702 relays are the latching type relays hold their state even after power has been removed all relay states are set to open a few seconds after either a power cycle or a RST command is issued For a 4 wire function or operation 34 RTD TEMP Ratio or Chann
85. lator tests There are three primary tests for an inflator e Shunt bar test e Bridgewire test e Insulation resistance HIPOT test NOTE Interlock The three primary tests can only be performed if the interlock of the 7751 7752 7755 module is enabled With interlock open disabled the I source of the 7751 7752 7753 module and the V source of the 7751 7753 module are disconnected from the switching module matrix Details on the interlock are pro vided in Section 5 The following information provides an overview of the three tests that are used to test an inflator The actual detailed procedures for these tests are provided in Section 5 Shunt bar test NOTE A shunt bar test is typically tested again after all other inflator tests are completed As a final test it verifies that it is safe to install the inflator in a vehicle A shunt bar shorting clip is used to short the bridgewire s to prevent accidental ignition when handling or installing the inflator However an oxide can form between the shunt and the inflator terminals It is this high resistance oxide that diminishes the ability of the shunt bar to act as an effective short across the bridgwire s Without a good contact short detonation could occur The measured resistance of a shunt bar is typically between 10 to 100mQ One method used for the shunt bar test is shown in Figure 1 2 In this case the dry circuit mode of the 7751 7752 7753 clamps voltage at 20mV 1mA maxi
86. leasing SHIFT and then pressing CARD As shown in Figure 2 5 the closed channels will scroll across the display The four dots identify the end of the channel string Use the ENTER key to pause and resume scrolling e Press EXIT to return to the normal display state NOTE For remote programming closed channels can be identified using ROUT MULT CLOS and ROUT MULT CLOS STAT see Table 2 3 Figure 2 5 Viewing closed channels Press Press Select SLOTx Slotl or Slot2 TI 77517752 7753 SLOTIx 77xx 101 114 118 Select module Shows channels 101 114 and 118 closed 7753 should be installed in slot 1 for rated accuracy Closed channels scrolled Model 2790 SourceMeter Switch System User s Manual Open interlock errors The 7751 7752 and 7753 modules have an interlock When the interlock is open disabled the I source 7751 7752 and 7753 and V source 7751 and 7753 are disconnected from the switching matrix Details on enabling the interlock are explained in Section 5 The fol lowing errors are associated with an open interlock Front panel messages INTRLCK OPEN is displayed briefly if you attempt to close channel 18 19 or 21 with interlock open With the INPUTS switch in the REAR position in readings will overflow OFLO when the interlock is open In the case of the OFLO readings for open interlock the IL1 or IL2 message will also be displayed I
87. lected source is isolated from the rest of the module e Channels 18 and 19 With these channels open the backplane of the Model 2790 is isolated from the switching module Open interlock errors Details on open interlock errors are provided in Section 2 see Open interlock errors The following explains the more common errors associated with open interlock Front panel messages e INTRLCK OPEN is displayed briefly if you attempt to close channel 18 19 or 21 with interlock open e With the INPUTS switch in the REAR position in readings will overflow OFLO when the interlock is open The ILI or IL2 message will also be displayed to identify which slot is in violation With both slots in violation IL1 message takes precedence Remote programming errors When an open interlock is first detected error 860 slot 1 interlock violation or 861 slot 2 interlock violation occurs e With interlock open error 224 parameter error occurs if you attempt to close chan nel 18 19 or 21 It also occurs if you use ROUT MULT OPEN to open channel 20 while interlock is open Shunt bar test The resistance of the shunt bar is typically 10 to 100m It is possible for the contact sur faces of a shunt bar to oxidize even in normal operating conditions The presence of any such oxides affects the resistance of the shunt bar It may be desirable to test the shunt under dry circuit conditions to prevent the breakdown of any oxid
88. lity of the user to use the size and type of cable wire that best suits your needs Keep in mind that Teflon insulated wire performs better in high humidity condi tions but it is not recommended when subjected to mechanical movement like a device handler Recommended cable wire Beldon 8899 cable wire which is stranded 18AWG in size with a thick rubber insulation rated for 5000V working voltage It is very flexible and mechanically durable NOTE The use of an outer protective cable shield is recommended to prevent damage to the wire insulation It should preferably have a foil shield tied to earth ground on one end to provide an extra layer of protection in the event that a wire conductor becomes exposed It will also serve to reduce measurement noise caused by nearby machinery A recommended cable shield is available from Zippertubing and covered later in this section 4 4 Model 2790 SourceMeter Switch System User s Manual Wiring procedure Use the following procedure to wire a 7751 7752 7753 or 7702 module Make sure to add supplementary insulation around the harness for voltages above 42V peak see Figure 4 4 NOTE Figure 4 2 and Figure 4 3 show channel identification for the 77511775217753 and 7702 modules Figure 4 4 shows how to wire a 7751 7752 7755 module Wiring for the 7702 module is similar WARNING WARNING CAUTION Do not connect 7751 7753 V source Hi to earth ground The 7751 7752 7753 module use
89. losed to test DUT 1 4 Switching Module Wiring and Installation Connections and wiring Provides the details needed to make connections to the screw terminals of the 7751 7752 7753 and 7702 modules Switching module installation Explains how to install a 7751 7752 7753 or 7702 in the Model 2790 mainframe 4 2 Model 2790 SourceMeter Switch System User s Manual Connections and wiring WARNING WARNING The following information is intended for qualified service personnel Do not make switching module connections unless qualified to do so To prevent electric shock that could result in serious injury or death adhere to following safety precautions Before removing or installing a switching module in the mainframe make sure the mainframe is turned off and disconnected from line power Before making or breaking connections to a switching module make sure power is removed from all external circuitry Do not connect signals that may exceed the maximum specifications of the module Specifications for the switching modules are pro vided in Appendix A Do not apply gt 42V between any terminal HI or LO and chassis ground Do not apply any external sources to the 7751 7752 7753 module NOTE 7702 allows measurement of external sources but use extreme caution single faults hardwarelsoftware could detonate airbag Screw terminals Screw terminals on the switching modules are used for connection to DUT an
90. lot number of the module being used Safety features The Model 2790 has built in safety features to reduce the possi bility of inflator ignition and damage to the module due to excessive current e Interlock The interlock feature of a 7751 7752 7753 module disconnects the sources I source and V source from the switching matrix Details on the interlock are provided in Section 5 e Fuses Current limiting fuses for the current source of the Model 2790 DMM and the I source of the 7751 7752 7753 module source current limiting An active high speed current limiting circuitry for the I source of the 7751 7752 and 7753 modules e V source current limiting An impedance circuit limits current to 1mA Model 2790 SourceMeter Switch System User s Manual 1 3 Technical terms The following defines and explains technical terms associated with airbag inflators Initiator Pyro technic device used to trigger the main gas charge generation action Sometimes referred to in classic military terms as a squib The term squib may be used to refer to the core element of an initiator explosive coated bridgewire or to the entire initiator Airbag inflator The gas generating assembly typically made of steel contain ing a stored chemical or pressurized inert gas or both and an electrical initiator Hybrid inflator An inflator that uses both pressurized gas and a chemical reaction to generate the ga
91. m User s Manual 5 25 Figure 5 12 Test circuit HIPOT Keithley 7751 7753 Inflator i i lt Inflator E Housing Shunt Interna Se e Bar RHIPOT VSQUE B shunts VMEAS 19 Leak 500V Qe T x 200kQ 7751 Under V MEAS IEEE E eS RHIPOT MM 500V x 20kQ 7753 VMEAS 22 Selects V source Input HI IV Amplifier 7751 7753 2790 DMM Input LO 9 Closed channel switch Test assumptions To test a single inflator connected to Bank 1 close channels 1 and 3 Closing channel 3 connects an internal built in shunt across the bridgewire To test a dual inflator connected to Banks 1 and 2 close channels 3 4 and 6 Closing channels 3 and 6 connects internal built in shunts across the two bridgewires NOTE Each channel except channel 23 is a 2 pole switch Therefore when a 2 pole channel is closed two switches close Channel 23 is a 1 pole switch see schematic in Figure 2 1 Open switches not used in the test circuit are not shown 5 26 Model 2790 SourceMeter Switch System User s Manual Test procedure HIPOT WARNING The following test procedure involves hazardous voltages It is the responsibility of the customer to operate instruments in a safe manner Be sure to read and follow the instructions for connecting and wiring the tester in Section 4 before operating the equipment NOTE To ensure the reliability of the HIPOT test it should be performed after ve
92. more detailed example Table 2 5 Basic memory pattern example ROUT MEM CHAN 1 108 115 118 Specify relays to close ROUT MEM DEL 1 0 Set memory delay 0 SENS FUNC RES M1 Select 2 wire ohms measurement function SENS RES RANG 100 M1 Select 10002 fixed measurement range SENS RES NPLC 1 M1 Set A D integration time to 1 power line cycle ROUT MEM REC 1 Recall Memory Location 1 READ Initiate a measurement and request the result ROUT OPEN ALL Open all relays Memory pattern command options All CALCulate SENSe and UNIT subsystem commands with a lt clist gt channel list parameter associated with Model 2790 DC volts 2 wire ohms and 4 wire ohms measure ment functions can include a memory pattern lt clist gt parameter Mn that allows you to assign those functions to specific memory pattern locations For example the following command selects the 2 wire ohms measurement function for memory pattern location 1 SENS FUNC RES M1 Once various attributes are assigned to memory pattern locations those functions will be executed when those memory pattern locations are recalled either individually or while scanning Memory pattern scanning To perform scanning with memory patterns simply include the memory pattern locations in place of channels in the scan list then set up and trigger a scan in the usual manner For exam ple the following command sets up a memory pattern scan for memory loca
93. mple count 1024 DETector BANDwidth 300 with nPLC 0 01 Maximum useful limit with trigger delay 175ms P Typical uncertainties Typical represents two sigma or 95 of manufactured units measure lt 0 35 of reading and three sigma or 99 7 lt 1 06 of reading For signal levels gt 2 2A add additional 0 4 to of reading uncertainty Internal Scanner Speeds Into and Out of Memory to GPIB 7702 Scanning DCV 60 s Internal Scanner Speed Notes Speeds are 60Hz or 50Hz operation using factory default conditions RST NPLC 0 01 Auto Zero off Auto Range off and Display off Sample count 1024 Includes measurement and binary data transfer out GPIB GENERAL SPECIFICATIONS POWER SUPPLY 100V 120V 220V 240V LINE FREQUENCY 50Hz to 60Hz and 400Hz automatically sensed at power up POWER CONSUMPTION 28VA OPERATING ENVIRONMENT Specified for 0 C to 50 C Specified to 80 R H at 35 C Altitude up to 2000 meters STORAGE ENVIRONMENT 40 C to 70 C BATTERY Lithium battery backed memory 3 years 23 C WARRANTY 1 year EMC Conforms to European Union Directive 89 336 EEC EN61326 1 SAFETY Conforms to European Union Directive 73 23 EEC EN61010 1 CAT I VIBRATION MIL PRF 28800F Class 3 Random WARM UP 2 hours to rated accuracy DIMENSIONS Rack Mounting 89mm high x 213mm wide x 370mm deep 3 5 in x 8 375 in x 14 563 in Bench Configuration with handle and feet 104mm h
94. mum for the constant test current of the I source This low voltage will not pierce the oxide With the low ohms math function SxIohms selected the Rspuynr reading can be read directly from the dis play of the Model 2790 Model 2790 SourceMeter Switch System User s Manual 1 7 Figure 1 2 Shunt bar testing 1 Keithley bos 1 7751 7752 i or7753 i Module Shunt Bar i Under 2790 VMEAS SOURCE IMA max Ru din I l l l Lle e e e DMM RSHUNT NOTE lfrequired a more accurate resistance measurement of the shunt bar can be achieved by disabling the dry circuit and using a test current of 50mA An even more accurate resistance measurement can be achieved using the Q4 function of the Model 2790 Keep in mind that this is an additional test and does not replace the test using the dry circuit NOTE Use this 2 step process to detect the presence of oxide build up and more accurately measure the resistance of the shunt bar l1 Test the shunt bar using dry circuit ohms channel 24 closed and a test current of ImA A resistance gt 100mQ indicates the presence of oxide build up 2 Accurately measure shunt bar resistance without dry circuit channel 24 open and a test current of 50mA or use the Q4 function of the Model 2790 Section 6 explains how to use the Q4 function of the Model 2790 with the 7702 or 7751 7752 7753 module Model 2790 SourceMeter Switch
95. n will perform cable discharge When the OPEN ALL operation is performed the following sequence of actions occur 1 Opens channel 21 to disconnect all sources 2 Opens channel 22 3 Closes channel 20 for 5msec to perform cable discharge 4 Opens all channels NOTE In Section 5 the test procedure for HIPOT uses the OPEN ALL operation to perform cable discharge see steps 7 and 11 in Table 5 6 2 18 Model 2790 SourceMeter Switch System User s Manual Manual cable discharge The discharge circuit can also be activated manually at any time by closing channel 20 of the 7751 7753 module Typically manual discharge is used when a discharge time 5msec is desired Figure 2 6 Cable discharge circuit Keithley 7751 7753 Source Sense Inflator i Under Test l LO Source e Closed channel switches Connection log Model 2790 SourceMeter Switch System User s Manual Make a copy of Table 2 4 and affix it to the cover of the 7751 7752 7753 module Use it to record connection information and channel descriptions as needed Table 2 4 Connection log Model 7751 7752 7753 CHI HI Source Sense Bank CH2 LO Source Sense CH3 Al Bl CH4 HI Source Sense Bank CH5 LO Source Sense CH6 A2 B2 CH7 HD Source Sense Bank CH8 LO Source Sense CH9 A3 B3 CH10 HD Source Sense Bank CH11 LO
96. nd of each test Table 5 2 Test procedure bridgewire Command Sequence Front Panel Operation 1 Reset 2790 and RST Press SHIFT gt press SETUP gt select RESTORE open all channels FACT 2 Set I source to SOUR CURR 0 05 127 Press SHIFT gt press CARD gt select CONFIG gt 50mA select SLOTI 7751 7752 or 7753 set I C27 to 50 00 mA press ENTER press EXIT or ENTER Select and enable CALC1 FORM S1I Press SHIFT gt press MATH gt select SIIOHMS the low ohms CALC1 STAT ON calculation Close channels to ROUT MULT CLOS Press CLOSE select MULTI select 101 select test bridgewire 0101 102 117 118 121 102 select 117 select 118 select 121 press EXIT Verify channels ROUT MULT CLOS Press SHIFT gt press CARD gt select VIEW gt select that are closed SLOTI 7751 7752 or 7753 Press EXIT when optional finished 6 Perform READ Take reading from display measurement 7 Open all channels ROUT OPEN ALL Press OPEN select ALL The following steps are used to test the second bridgewire of a dual stage inflator 8 Close channels to ROUT MULT CLOS Press CLOSE gt select MULTI gt select 104 gt test 2nd bridgwire 104 105 117 118 121 select 105 gt select 117 gt select 118 gt select 121 gt press EXIT 9 Verify channels ROUT MULT CLOS Press SHIFT press CARD select VIEW select that are closed SLOTI 7751 7752 or 7753 Press EXIT when
97. nels to ROUT MULT CLOS Press CLOSE gt select MULTI gt select 104 gt select perform HIPOT 104 106 108 116 118 121 106 gt select 108 gt select 116 gt select 118 gt select test for second 122 223 121 select 122 select 123 press EXIT bridgewire Model 2790 SourceMeter Switch System User s Manual 5 27 Table 5 6 cont Test procedure HIPOT Test Step Command Sequence Front Panel Operation 9 Verify channels ROUT MULT CLOS Press SHIFT press CARD select VIEW select that are closed SLOT1 7751 or 7753 Press EXIT when finished optional 10 Perform READ Take reading from display measurement Perform cable ROUT OPEN ALL Press OPEN gt select ALL discharge and open all channels Test step notes 1 Resetting the 2790 opens all channels selects the DCV function auto range and selects the I source of the 7751 7753 module For remote programming RST places the 2790 in the one shot trigger mode For front panel operation FACT defaults places the 2790 in the continuous trigger mode 2 This step sets the V source to output 500V which is a typical voltage for this test Note that this menu is also used to set the I source output Simply skip over the I source setting This step selects the high resistance calculation R Vsour IygAs Selecting SIVOHMS sets the DMM to DCV 10V range This step closes the channels to make the test connections for the HIPOT test It assume
98. nnections Figure 5 2 Use this connection scheme if using a Keithley 7752 module It can also be used for the 7751 or 7753 module if not performing the HIPOT test Figure 5 3 Use this connection scheme if using a Keithley 7751 or 7753 mod ule It includes the connections for the HIPOT test Figure 5 2 Test connections shunt bar and bridgewire testing single stage inflator Single Stage Inflator Keithley 7751 7752 or 7753 A Shunt Bar Testing B Bridgewire Testing Bank 1 SRC HI Shunt SEN HI Bar SRC LO SEN LO Figure 5 3 Model 2790 SourceMeter Switch System User s Manual Test connections shunt bar HIPOT and bridgewire testing single stage inflator Keithley 7751 7753 Bank 1 J101 SRCHI SEN HI OWS SRC LO a Qo SEN LO ONS S Bank 3 J103 SRC HI S SEN HI e scio O SEN LO OIS S Single Stage Inflator A Shunt Bar and HIPOT Testing NOTE NOTE Bridgewire Testing Built in shunt Available for use during HIPOT testing Channel 3 closed for HIPOT and open for shunt bar and bridgewire tests Some wires are shown in bold to make it easier to follow the signal paths For high ohms measurements gt 1GQ it is recommended that the DUT be connected between two different banks for example Bank 1 and Bank 3 as seen in test connection figures to reduce the possibility of measurement error caused by leakage resistance Model
99. nnels 3 and 6 are closed for HIPOT and open for shunt bar and bridgewire tests NOTE Some wires are shown in bold to make it easier to follow the signal paths NOTE For high ohms measurements gt 1 GQ it is recommended that the DUT be connected between two different banks for example Bank 1 and Bank 3 as seen in test connection figures to reduce the possibility of measurement error caused by leakage resistance Model 2790 SourceMeter Switch System User s Manual 5 9 Interlock connections Figure 5 6 When using a test fixture or safety shield that has an interlock switch con nect interlock as shown in Figure 5 6 Figure 5 6 Interlock connections Eee ee eee eee eee ee eee eee ee eee ee ee Ee Keithley 7751 7752 or 7753 J106 INTERLOCK 5V Test Station Connect to safety earth ground using 18 AWG wire or larger INTERLOCK Lid shield open switch open Sources disconnected Lid shield closed 2 switch closed 2 Sources connected WARNING DO NOT permanently short out the interlock Interlock is an essential safeguard to prevent personal injury due to electric shock and or accidental ignition of an inflator It is a good safe practice to use an interlock test station that always disables the sources and provides protection from inflator ignition Interlock NOTE An enabled interlock allows the I source and V source 7751 7753 to be con nected to the rest of the switch matrix An
100. nsacadosdsesennstadeansuiseannaraiecteticesmcerines 5 30 Model 2790 DMM Ohms Functions Using W2 function to measure resistance cceeeeceeeeeeeeeees 6 3 Using W4 function to measure resistance ccceeceeeeeeeeeeees 6 4 Using Model 2790 4 wire ohms with 7702 module low ohms measurements eeeer nne 6 6 Using Model 2790 2 wire ohms with 7702 module high ohms measurements 25 9 mtr ro nro ire ie aed 6 7 Using Model 2790 4 wire ohms with 7751 7752 7753 module low ohms measurements eene 6 8 Using Model 2790 2 wire ohms with 7751 7752 7753 module high ohms measurements 6 9 List of Tables 2 Table 2 1 Table 2 2 Table 2 3 Table 2 4 Table 2 5 Table 2 6 3 Table 3 1 Table 3 2 5 Table 5 1 Table 5 2 Table 5 3 Table 5 4 Table 5 5 Table 5 6 Table 5 7 Table 5 8 6 Table 6 1 Keithley 7751 7752 and 7753 Switching Modules Commands to set amplitude for V source and I source 2 8 Commands to select ohms calculations 2 12 Commands to control 7751 7752 7753 module channels 2 14 Connection los Model 7751 7752 T1593 iius sesessssse2 2 19 Basic memory pattern example eeeeeeeeeeeeenee 2 22 Memory pattern TOS osusccsomisdsb Macao EDE FIN RoHS neii 2 23 Keithley 7702 Switching Module Connection log Model 7702 tiseesuentsienvanitrani ns oia t amies 3 8 Commands to
101. oltage Vp across RDUT Figure 6 1 Using Q2 function to measure resistance imaghiago7on 4 Test Current Keithley 2790 i Input HI RLEAD ISOURCE 1mA eee Vmeas Voltage measured by 2790 DMM Vr Voltage across RDUT V RMEAS s Rout 2 x RLEAD Iso V RDUT SOUR Model 2790 SourceMeter Switch System User s Manual The 4 wire Kelvin connection method shown in Figure 6 2 should be used for low resis tance measurements With this configuration the test current is forced through Rpyy through one set of test leads while the voltage is measured through a second set of test leads called sense leads Due to the high impedance of the DMM of the Model 2790 negligible current will flow through the sense leads Since the voltage across the sense leads will be negligible the voltage measured by the DMM Vmeas is essentially the same as the voltage across the DUT Vp Figure 6 2 Using Q4 function to measure resistance Input HI P Test Current Sense LO Input LO Vmeas Voltage measured by 2790 DMM Vr Voltage across RDUT Because sense current is negligible Vmeas VR Therefore ISOUR ISOUR Model 2790 SourceMeter Switch System User s Manual 6 5 Offset compensated ohms The presence of thermal EMFs Vgmp can adversely affect low resistance measurement accuracy To overcome these unwanted offset voltages you can use offset compensated ohms OCOMP Offset compensated
102. onnections see Figure 3 2 24 and RTD temperature connections see Figure 3 3 Current connections DCI or ACI see Figure 3 4 Voltage connections DCV or ACV see Figure 3 5 Figure 3 2 Q2 and thermistor TEMP connections 7702 HI Channel 1 LO Resistors or Thermistors HI Channels 2 39 Channel 40 3 6 Model 2790 SourceMeter Switch System User s Manual Figure 3 3 Q4 and RTD TEMP connections 7702 HI Resistor or C ranne z 4 Wire RTD LO O Channels 2 19 o ue Ch 120 Resistor or s IEI 4 Wire RTD LO o HI Channel 21 LOO Channels 22 39 HI Channel 40 NOTE For details on using the 7702 module to make ohms measurements see Section 6 Model 2790 DMM Ohms Functions Figure 3 4 Current connections DCI and ACI Channel 41 HI Channel 42 LO Model 2790 SourceMeter Switch System User s Manual 3 7 Figure 3 5 Voltage connections DCV or ACV DC Voltage AC Voltage a lt 7702 HI Channel 1 L Channels 2 39 M lt e lt HI ot Channel 40 L al fee cease eee Connection log Make a copy of Table 3 1 and affix it to the cover of the Model 7702 Use this to record connection information and channel descriptions as needed Model 2790 SourceMeter Switch System User s Manual Table 3 1 Connection log Model 7702
103. ose terminal blocks J105 J107 and J108 for additional details General purpose terminal blocks J105 J107 and J108 There are quick disconnect terminal blocks available to the user to provide access to various switching module components These are provided for general purpose test applications that are not necessarily related to airbags J105 matrix backplane and guard The backplane terminals provide access to the relay matrix backplane The matrix backplane is the primary artery for signal routing though the module The guard terminals are typically used for shielding when using the V source and I V con verter for high ohms measurements Guard connections are explained in Section 4 J107 source outputs and guard The I source and V source 7751 7753 are always on and can be accessed by the user at J107 The programmed output is routed to these terminals The guard terminals are typically used for shielding when using the V source and I V converter for high ohms measurements Guard connections are explained in Section 4 2 6 Model 2790 SourceMeter Switch System User s Manual J108 I V converter The user also has access to the input output and ground of the I V converter at J108 Safety warnings WARNING Integrated safety features protect the 7751 7752 7753 module from its built in I source and V source However if an external source such as the 12V car bus is connected to the front panel inputs of the
104. ource output levels Press Press Select CONFIG Z7XX 7751 7752 7793 SLOT1 77xx Set I source 7751 I C27 01 00 mA cu I C27 01 00 mA 7752 SES 7753 Set V source l 7751 V C28 050 0 V output V C28 050 0 V 775 3 7753 should be installed in slot 1 for rated accuracy SLOT2 77xx Select module 7751 7752 77 53 7751 7753 2 8 Model 2790 SourceMeter Switch System User s Manual Remote programming As shown in Table 2 1 the amplitude command is used to set the outputs of the sources Notice that the channel number of the V source 28 and I source 27 must be included in the command string Table 2 1 Commands to set amplitude for V source and I source SOURce VOLTage LEVel IMMediate AMPLitude lt NRf gt lt clist gt Set V source output 50 to 500 V 50V lt clist gt 128 Slot 1 228 Slot 2 AMPLitude lt clist gt Query V source output level SOURce CURRent LEVel IMMediate AMPLitude lt NRf gt lt clist gt Set I source output 0 to 50 mA lt clist gt 127 Slot 1 227 Slot 2 AMPLitude lt clist gt Query I source output level Note Selecting an ohms calculation enables source tracking Selecting any other math function disables source tracking Model 2790 SourceMeter Switch System User s Manual 2 9 Math There is a shortcut math function to calculate low resistance when using the I source of a 7751 7752 7753 mod
105. oving 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 Al ways 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 equipment may be impaired Do not exceed the maximum signal levels of the instruments and accessories as defined in the specifications and operating in formation 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 applied 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 N symbol on an instrument indicates that the user should refer to the operating instructions located in the manual The N symbol on an instrument shows that it can source or measure 1000 volts or more including the combined effect of normal and common mode voltages Use standard safety precautions to avoi
106. 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 service personnel may perform installation and service procedures Keithley products are designed for use with electrical signals that are rated Measurement Category I and Measurement Category II as described in the International Electrotechnical Commission IEC Standard IEC 60664 Most measurement control and data I O signals are Measurement Category I and must not be directly connected to mains voltage or to voltage sources with high transient over voltages Measurement Category II connections require protection for high transient over voltages often as sociated with local AC mains connections Assume all measurement control and data I O connections are for connection to Category I sources unless otherwise marked or described in the Manual 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 ANST 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 Operators of this product must be protected from electric shock at all times The responsible body must ensure that operators are prevented access
107. re 3 6 can be used to select the next or previous input channel Figure 3 6 and gt keys C Close previous N x Close next input channel input channel With the first 7702 input channel closed displayed pressing the lt key opens the closed input channel With the last 7702 input channel closed displayed pressing the key opens the closed input channel CLOSE key As shown in Figure 3 7 the SINGLE option of the CLOSE key can be used to close an input channel while the MULT option can be used to close multiple channels Figure 3 7 CLOSE key A Closing a single channel B Closing multiple channels Press CLOSE key Press CLOSE key Display MULT option Display SINGLE option and oress ENTER and press ENTER CLOSE SINGLE CLOSE MULT i Specify channel number Specify channel number CLOSE MULT XXX XXX d ENTER CLOSE CH XXX XXX and press ENTER l Jang press Model 2790 SourceMeter Switch System User s Manual OPEN key As shown in Figure 3 8 the OPEN ALL option of the OPEN key opens all channels in the mainframe both slots while OPEN MULT opens multiple selected channels NOTE Fora7751 7752 7753 module the OPEN ALL operation will not open channel 20 if the interlock is open Figure 3 8 OPEN key OPEN CLOSE Press OPEN key OPEN MULT Display channel number OPEN MULT XXX XXX and press ENTER Display MULT option Display ALL option and press ENTER and press OPEN aga
108. rifying contact Contact checks and the output of the V source V source readback Single stage inflator Perform Test Steps 1 through 7 in Table 5 6 Dual stage inflator Perform Test Steps 1 through 11 in Table 5 6 Table 5 6 Test procedure HIPOT Test Step Command Sequence Front Panel Operation 1 Reset 2790 and RST Press SHIFT press SETUP select RESTORE open all channels FACT 2 Set V source to SOUR VOLT 500 60128 Press SHIFT press CARD select CONFIG 500V Include a 250msec program delay to select SLOT1 7751 or 7753 gt display V C28 gt set allow source to settle to 500 0 V Select and enable CALC1 FORM S1V Press SHIFT press MATH select SIVOHMS the high ohms CALC1 STAT ON calculation Close channels to ROUT MULT CLOS Press CLOSE select MULTI select 101 select perform HIPOT 101 103 108 116 118 103 gt select 108 gt select 116 gt select 118 gt select test 121 122 123 121 gt select 122 gt select 123 gt press EXIT Verify channels ROUT MULT CLOS Press SHIFT gt press CARD gt select VIEW gt select that are closed SLOT2 7751 or 7753 Press EXIT when finished optional Perform READ Take reading from display measurement Perform cable ROUT OPEN ALL Press OPEN gt select ALL discharge and open all channels The following steps are used to test insulation resistance for the second bridgewire of a dual stage inflator 8 Close chan
109. s a floating ground This floating ground is not connected to safety earth ground Not only will it create a shock hazard by floating up to 500V it will also effectively connect a 1nF capacitor across the V source providing energy storage that could ignite an airbag under fault conditions All wiring and supplementary insulation must be rated for the maxi mum voltage in the system For example if 500V is being used in the test system the module wiring for both slots must be rated for at least 500V For the 7751 7753 be sure not to dislodge the thermal pad on the volt age source Also be sure to use only the top cover with the integral heat sink to assure proper voltage source operation 1 Make sure all power is discharged from the switching module Access the screw terminals see Figure 4 1 3 Using a small flat blade screwdriver loosen terminal screws and install wires as desired Figure 4 4 shows 7751 7752 7753 connections to channels 1 and 2 and the interlock 4 Route wire along wire path and secure with cable ties as shown Note that the wires leading out of the module should be encased in a ground wrap see Zippertubing 9 shield 5 Hill in a copy of the connection log Table 2 4 for the 7751 7752 7753 and Table 3 1 for the 7702 and affix it to the module cover 6 Close and lock cover Model 2790 SourceMeter Switch System User s Manual 4 5 Figure 4 2 Model 7751 7752 7753 screw terminal channel design
110. s charge for bag inflation Airbag or Airbag module The fully functional device including initiator inflator textile bag and mounting frame or enclosure E check Industry standard term for electrical testing of airbag inflators and modules Consists of two basic resistance measurements Test continuity of the bridgewire typically 2 to 3 ohms using a constant current method typically 10 to 50mA HIPOT test Measure the insulation resistance 2100M 2 between the bridgewire and the inflator housing using an applied voltage typically 500V HIPOT Used in this manual to describe the high resistance measurements made using high voltage The intent is not to break down the insulator but to measure the leakage current that flows through the insulator Body check contact check Prior to HIPOT testing connections to the inflator housing must be verified This is necessary because an open connection would result in a reading that appears to be the resistance of the insulator but would instead be a high resistance reading that is the result of an open circuit Shorting clip shunt bar For handling and transport safety against ESD electro static discharge or other accidental discharge every inflator module has a spring loaded clip that shorts the initiator squib pins together when a connector is not installed The connection cables also include shorting clips since many inflator modules have cables attac
111. s the single stage inflator is connected as shown in Figure 5 3 This step is optional Use it to verify that the correct channels are closed for the test For remote programming READ triggers and requests a single reading Performs cable discharge for input channels 1 and 2 and opens all channels This step closes the channels to make the test connections for the second HIPOT test It assumes the dual stage inflator is connected as shown in Figure 5 5 9 This step is optional Use it to verify that the correct channels are closed for the test 10 For remote programming READ triggers and requests a single reading 11 Performs cable discharge for input channels 4 and 5 and opens all channels e W oO 1 QN tA 5 28 Model 2790 SourceMeter Switch System User s Manual I source readback This readback circuit measures the actual current that is flowing in the test circuit through the DUT bridgewire or shunt bar It is used to verify that the programmed current level of the I source is being used in the tests NOTE lI source readback is only accurate to 1 It is only intended as a verification and not a high accuracy measurement The I source readback circuits are shown in Figure 5 13 Figure 5 13A shows how to measure the current for the bridgewire test while Figure 5 13B shows how to measure the current for the shunt bar test In both circuits the Model 2790 DMM measures the voltage across the 1 2 resistor
112. setting can be global to all qualified channels or set on a per channel basis by using the lt clist gt parameter NOTE With an ohms math function selected the Model 2790 is actually measuring DCV Therefore if you send SENSI FUNC to query the selected function it will return VOLT DC Source tracking The Model 2790 provides source tracking to ensure that the most recently set source amplitude is used in the selected ohms calculation If the source output level changes the m constant for the calculation will change accordingly Source tracking is enabled automatically when the desired ohms function is selected No other actions are required by the user However if desired source tracking can be disabled or the source that is being tracked can be changed The TRACK and SOURCe commands are listed in Table 2 2 2 12 Model 2790 SourceMeter Switch System User s Manual Table 2 2 Commands to select ohms calculations CALCulate 1 FORMat lt name gt Select math function NONE MXB PERC PERCent RECiprocal S1Iohms S1Vohms S21ohms S2Vohms CALCulate 1 FORMat Query selected math format CALCulate 1 STATe lt b gt Enable or disable math calculation CALCulate 1 STATe Query state of selected math calculation CALCulate 1 DATA LATest Return last result of calculation CALCulate 1 DATA FRESh Return last fresh result of calculation The following commands are set automatically when an ohms math function Sx
113. sirrrssieieeisereitene ieseni nka 2 6 Remote programming eeeessseeessssssssssssssssssssssssssssssseesseeeese 2 8 KE e A A E E E 2 9 Front panel operation eeeesssesssssssssssssssssssssssssssessssseeeeeeees 2 11 Remote programming oioccukotciusus tubis edtao wsacearccheducedoalseeees 2 11 Opening and closing channels eeeeeeeeeeeeeeeeeeeee 2 13 Front panel operation oj circ css vore Ue tOEEE UNUM tu dusudd etd Msckdss 2 13 Remote programming 1 rns rtm Iu etra d rore nore 2 14 Viewing closed channels MENT Tm 2 15 Open interlock errors ssesesseeeeseesereererrereerreeressesssssesssssssssss 2 16 Cable discharge circuit 7751 and 7753 assetto 2 17 Srouveaisu o ARRIERE 2 19 Using memory patterns agenesis screen ineocae ctu meedeincebesussdoeanlousin 2 20 Firmware revision level ooicooaisesosstoedietesuo torte vu etu tore omissis 2 20 Sl A 2 20 Front panel operation wcsiainscavdivseuscenerncateinss opsasausiinewanednadenend 2 20 Memory pattern commands 42 io icecese peret vhi neben 2 2 Setting up and executing memory patterns 2 2 Memory pattern command options cceeeeeeeeeeeeeeeees 2 22 Memory pattern scanning cccccseeecceeeecceceeceeeeeeeeeeeees 2 22 Memory pattern log possi cueeicuuvus tab bu cut ap Gad s uisa t deua d CH RE uis 2 23 Keithley 7702 Switching Module Dates PECCANCIONS sessies nE EEE Eea 3 2 Card conf
114. sistance The resistance of these fuses is fairly temperature sensitive Typically a short measured right at the channel terminals reads between 12 2 cold to approximately 15 2 hot Although not usually a problem you can correct for this offset using the REL function of the DMM subtract the offset from the readings in your test pro gram or you can simply adjust pass fail limits NOTE Fuse resistance does not affect 4 wire measurements which sense around the lead resistance Model 2790 SourceMeter Switch System User s Manual 6 3 High ohms measurements The 7751 and 7753 include a programmable V source 50 to 500V so the constant volt age method can be used to measure high resistance such as insulation resistance The Model 2790 mainframe does not have a voltage source If not using a 7751 or 7753 module in your test system you can use the Q2 function 100M Q range of the Model 2790 to measure insulation resistance up to 120MQ 4 wire ohms 4 wire ohms eliminates the effects of test lead resistance when measuring a low ohms DUT Figure 6 1 shows how 2 wire ohms can be adversely affected when measuring a low ohms DUT If the test lead resistance Ry gap is relatively large in comparison to the resistance of the DUT Rpur the measured voltage Vmgas will include the voltage drops across the two test leads Therefore the measured voltage which is used to calculate resistance will not be the same as the actual v
115. t System 1 5 Overview 1 1 testing two inflators 1 4 Typical connections Model 7702 3 5 typical test system 1 5 Viewing closed channels Model 7702 3 12 Model 7751 7752 2 15 V source and I V amplifier 2 4 output levels 2 6 readback 1 10 warnings 2 6 Wiring 4 1 Zippertubing 4 8 Specifications are subject to change without notice All Keithley trademarks and trade names are the property of Keithley Instruments Inc All other trademarks and trade names are the property of their respective companies KEI I HLEY A GREATER MEASURE OF CONFIDENCE Keithley Instruments Inc Corporate Headquarters 28775 Aurora Road Cleveland Ohio 44139 e 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 e www keithley com Belgium Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 www keithley nl China Beijing 8610 82251886 Fax 8610 82251892 www keithley com cn Finland Helsinki e 09 5306 6560 Fax 09 5306 6565 www keithley com France Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 www keithley fr Germany Germering 089 84 93 07 40 Fax 089 84 93 07 34 www keithley de Great Britain Theale 0118 929 7500 Fax 0118 929 7519 www keithley co uk India Bangalore 080 212 8027 Fax 080 212 8005 www keithley com Italy Milano 02 48 39 16 01 Fax 02 48 30 22 74 www keithley it Japan Tokyo 81 3 5733 7555 Fax 81 3 5733 7556 www keithley jp Korea Seoul 82 2 574 777
116. ted for by measuring a zero ohm load short circuit and then using the REL function see Section 5 of the Model 2790 Refer ence Manual to remove the offset 4 wire ohms measurements are not affected by the safety circuitry Figure 6 6 Using Model 2790 2 wire ohms with 7751 7752 7753 module high ohms measurements o cud P 2 ac AE LEA ELM rs Eric E cd cic i I I I I Keithley 2790 Fuse Keithley 7751 7752 7753 Resistance Input Hl 18 13 10 Gore CHA lt 120MQ Ch 11 69 Channel closed by user multiple channel operation 6 10 Model 2790 SourceMeter Switch System User s Manual A Specifications Models 2790 7751 7752 7753 and 7702 e Models 2790 7751 7752 7753 specifications Provides the complete instrument specifications for the Model 2790 SourceMeter Switch System including the specifications for the Models 7751 7752 and 7753 modules e Ohms specification calculations 7751 7752 7753 Provides equations to calculate ohms specifications for source levels not specified in the 7751 7752 7753 module specifications e Model 7702 specifications Provides the complete specifications for the Model 7702 module 2790 SourceMeter Switch System Specifications 7751 7752 7753 SOURCE SWITCH MODULE SPECIFICATIONS 2790 Resistance Mode Specifications with Cards Module function accuracy specifications are for 2 years 23 C 5 C Typ Open Source Maximum Ckt Accuracy Temperat
117. tely execute memory pattern lt n gt ROUTe MEMory READ STATe lt n gt lt b gt If set to ON a reading will be collected after the memory pattern has executed applies to scanning only ROUTe MEMory CLEar lt n gt Clear out memory pattern lt n gt setting all channels to open and removing all digital and analog channels from this memory pattern ROUTe MEMory CLEar ALL Clear out all memory patterns You must include at least one measurement channel or a memory pattern that takes a reading ROUT MEM READ STAT x ON Failure to do so results in the scan list being rejected with Error 702 No measurement channel in scanlist Setting up and executing memory patterns To set up memory patterns use the following procedure 1 Program the desired memory pattern locations using the ROUT MEM commands Typically you would set source value s define channels to close and set up delay for each memory location 2 Define DCV 2 wire ohms or 4 wire ohms measurement function s for each memory pattern location 2 22 Model 2790 SourceMeter Switch System User s Manual 3 Once a location is defined use the ROUT MEM REC command to recall a mem ory pattern location then trigger and acquire a reading using READ 4 After taking the measurement use ROUT OPEN ALL to open all channels An example that sets up and executes memory location 1 is shown in Table 2 5 See Memory patterns test on page 5 30 for a
118. ter Switch System User s Manual 6 7 Figure 6 4 shows the simplified test circuit for using the 22 function of the Model 2790 with the 7702 module to measure high ohm DUT e insulation resistance up to 120MQ The DUT is connected to channel 1 of the 7702 When channel 1 is closed using system channel operation the DUT connects to the DMM of the Model 2790 Figure 6 4 Using Model 2790 2 wire ohms with 7702 module high ohms measurements Keithley 7702 LT Input HI lt 120MQ Input LO 9 Channel closed by user system channel operation Not shown is the backplane channel Ch 45 that also closes when channel 1 is closed 6 8 Model 2790 SourceMeter Switch System User s Manual Keithley 7751 7752 and 7753 modules The 7751 7752 and 7753 modules can also be used with the 22 and 24 functions of the Model 2790 However since these modules do not support system channel operation the user must close all appropriate channels using multiple channel operation to make the con nection to the DUT Details on multiple channel operation are provided in Section 2 Figure 6 5 shows the simplified test circuit for using the 24 function of the Model 2790 with the 7751 7752 7753 module to measure the resistance of a DUT The DUT is con nected to channels 10 and 11 Bank 4 of the 7751 7752 7753 To connect the DUT to the DMM of the Model 2790 channels 10 11 13 18 and 19 must be closed Note that the
119. termine temperature coefficient for a V source setting of 100V of reading 0 02 6 100 9o C 0 02 0 06 C 0 08 C Ohms temperature coefficient 100V 0 08 200 2 C Model 2790 SourceMeter Switch System User s Manual Specifications A 11 For measurements 100MQ to 1GQ Ohms accuracy o of reading 2 510 Vsougcg Ohms offset 20kQ where Voourcg 1s the voltage output setting in volts Example Determine ohms accuracy for a V source setting of 100V of reading 2 510 100 2 5 1 7 1 Ohms accuracy 100V 7 1 20kQ Ohms temperature coefficient TC of reading 0 02 51 VgourcE C TC ohms offset 200Q C where Voourceg is the voltage output setting in volts Example Determine temperature coefficient for a V source setting of 100V of reading 0 02 51 100 C 0 02 0 51 C 01 53 C Ohms temperature coefficient 100V 0 53 200 2 C A 12 Specifications Model 2790 SourceMeter Switch System User s Manual Index airbag inflators 1 2 Bridgewire test 1 8 bus programming 2 8 2 11 Cable discharge 2 4 circuit 2 17 2 18 Cabling requirements 4 3 Card configuration Model 7702 3 3 Models 7751 and 7752 2 2 Channel assignments Model 7702 3 9 Channels closing Model 7702 3 9 Model 7751 7752 2 13 Numbering 2 13 3 9 CLOSE key 3 10 5 2 Command Sequence bridgewire 5 15 contact checks 5 20 5 21 5 3
120. the 24 function To select 1kQ range let n 1e3 To select 10kQ range let n 10e3 6 6 Model 2790 SourceMeter Switch System User s Manual Keithley 7702 module The 40 two wire or 20 four wire input channels of the 7702 module make it ideal to test multiple DUT With system channel operation a single channel closure connects a DUT to the Model 2790 DMM for measurement Testing multiple DUT can be further automated using the scanning feature of the Model 2790 Once configured the testing process can be started with a single press of a button or when commanded for remote programming NOTE Details on scanning 7702 channels are provided in Section 7 of the Model 2790 Reference Manual Figure 6 3 shows the simplified test circuit for using the 24 function of the Model 2790 with the 7702 module to measure low ohm DUT The DUT is connected to channels 1 and 21 of the 7702 When channel 1 is closed using system channel operation the DUT con nects to the DMM of the Model 2790 Figure 6 3 Using Model 2790 4 wire ohms with 7702 module low ohms measurements lt ee a o o a a a a a a ee ee ee eee el Keithley 2790 ee er Keithley 7702 Input HI DUT 9 Channel closed by user system channel operation The channels that also close when Ch 1 is closed are not shown These include the paired input channel Ch 21 the 4 pole relay Ch 43 and backplane channels Chs 44 and 45 Model 2790 SourceMe
121. the HI terminal of the bridgewire e Bank 2 housing contact Close channels 8 15 and 18 to check the connection at the housing of the inflator Dual stage inflator As shown in Figure 5 10 there are four contact connection points for the V source test circuits Contact checks are performed as follows e Bank 1 HI contact Close channels 1 14 and 18 to check the connection at the HI terminal of bridgewire A e Bank 2 housing contact Close channels 8 15 and 18 to check the connection at the housing of the inflator e Bank 3 HI contact Close channels 4 14 and 18 to check the connection at the HI terminal of bridgewire B Model 2790 SourceMeter Switch System User s Manual 5 19 Figure 5 9 Test circuits contact check single stage inflator Internal 0 062A fuses not shown see Section 6 2790 23 Contact Point DMM 1 of 2 2790 Single Stage DMM Inflator Q E TE TA NOTE Each channel is a 2 pole switch Therefore when a Test assumptions channel is closed two Inflator housing connected to Bank 3 switches close see Inflator bridgewire connected to Bank 1 schematic in Figure 2 1 Figure 5 10 Test circuits contact check dual stage inflator Internal 0 062A fuses not shown see Section 6 2790 DMM Contact Point 2790 1 of 3 DM Dual Stage Inflator 9 Closed channel switch NOTE Each channel is a 2 pole Test assumptions switch Therefore when a In
122. the memory patterns feature which can be used to simplify repetitive test procedures 2 2 Model 2790 SourceMeter Switch System User s Manual NOTE Module wiring and installation into the mainframe of the Model 2790 is covered in Section 4 Details on using the Keithley 7751 7752 7753 modules to test inflators are provided in Section 5 The edit keys left right up and down arrow keys are used to display menu items and output levels With the desired menu item or output level displayed it is selected by pressing ENTER For remote programming the clist parameter is used as follows lt clist gt SCH where S Mainframe slot number 1 or 2 CH Switching module channel number of source 2 digits Examples QIOI Slot 1 Channel 1 QIOI 114 118 Slot 1 Channels 1 14 and 16 Card configuration CAUTION External energy sources should never be applied directly to a 7751 7752 or 7753 module for any reason Damage to the module and any connected devices under test can result due to the application of improperly selected or performing external energy sources The simplified schematic for the 7751 7752 and 7753 is provided in Figure 2 1 e Channels 1 12 Input channels for DUT inflator e Channels 13 19 and 25 Routes test signals to backplane of Model 2790 e Channels 20 24 27 and 28 Control individual components of the 7751 7752 7753 Model 2790 SourceMeter Switch System User s Manu
123. the negative value of m will cause the ohms reading to be displayed as a positive value When using the high ohms calculation Sx Vohms the highest DCV measurement range that can be selected is 10V Attempting to select a higher range will cause error 222 Parameter out of range If V 10mV an overflow will occur If V lt 12V an underflow will occur Attempting to turn Autoranging on generates error 221 Settings conflict over the GPIB or a NO AUTORANGE message on the display if done from the front panel AUTO key NOTE Readings for both the 7751 and 7753 modules will overflow when the I V output is greater than 9mV and underflow when the I V output is less than 12V Model 2790 SourceMeter Switch System User s Manual 2 11 Front panel operation An ohms math function is enabled from the MATH menu which is accessed by pressing and releasing SHIFT and then MATH see Figure 2 3 Note that an ohms math function is only available in the menu if the associated 7751 7752 or 7753 module is installed Figure 2 3 Enabling ohms math function Press SHIFT Press MATH STIOHMS STVOHMS S2IOHMS S2VOHMS 7751 7752 7753 7751 7753 77517752 7753 7751 7753 in slot 1 in slot 1 in slot 2 in slot 2 Select math function 7753 should be installed in slot 1 for rated accuracy Remote programming As shown in Table 2 2 the CALC FORMat command is used to select an ohms math function Notice that the math
124. tions 1 3 and 5 ROUT SCAN M1 M3 M5 Model 2790 SourceMeter Switch System User s Manual 2 23 Memory pattern log Table 2 6 provides a log for you to record the stored parameters for each memory location Table 2 6 Memory pattern log Memory location Source level s Delay Channels Functions 2 24 Model 2790 SourceMeter Switch System User s Manual Table 2 6 cont Memory pattern log Memory location Source level s Delay Channels Functions 3 Keithley 7702 Switching Module e Safety precautions Follow these safety precautions before using the 7751 7752 7753 modules with the 7702 module e Using 7751 7753 V source with 7702 module Explains how to use the 7751 7753 V source with the 7702 module Includes a test circuit diagram to explain this application e Card configuration Provides the simplified schematic of the Keithley 7702 switching module Summarizes key aspects of the module Typical connections Shows typical module connections for the various measurements Includes a connection log to record connection information and channel descriptions Opening and closing 7702 channels Explains how to open and close channels for the 7702 module e Viewing closed channels Explains how to display closed channels on the Model 2790 3 2 Model 2790 SourceMeter Switch System User s Manual NOTE Installation of Keithley switching modules in the mainframe of the Model 2790 is
125. to Bank 2 schematic in Figure 2 1 Model 2790 SourceMeter Switch System User s Manual Test procedure 5 31 The basic test procedure for using memory patterns to perform contact tests on a dual state inflator using scanning is shown in Table 5 7 The same test procedure using individual memory pattern location recall is shown in Table 5 8 This procedure sets up three memory locations for the necessary relay closures Each memory location is set up as follows Delay Os Function 2 wire ohms Range 100 Integration period 1 PLC After setting up memory locations Table 5 7 the scan is enabled triggered and readings are stored in the buffer for recall once the scan is complete For the memory pattern loca tion recall shown in Table 5 8 memory locations are first set up and each location is recalled in succession Table 5 7 Command sequence for memory patterns test example using scanning RST ROUT MEM CLE ALL Set up memory location I ROUT ROUT ROUT SENS SENS SENS MEM CHAN 1 101 114 118 MEM DEL 1 0 MEM READ STAT 1 ON FUNC RES M1 RES RANG 100 M1 RES NPLC 1 M1 Set up memory location 2 ROUT ROUT ROUT SENS SENS SENS MEM CHAN 2 104 114 118 MEM DEL 2 0 MEM READ STAT 2 ON FUNC RES M2 RES RANG 100 M2 RES NPLC 1 M2 Restore GPIB defaults Clear all memory pattern locations Set channels 1 14 and 18 for memory location 1 Set del
126. to ensure that the programmed voltage is being used e Cable discharge Summarizes cable discharge which is used to dissipate energy stored in the test cables and the module by the V source e HIPOT test This test measures the insulation resistance of the inflator Single stage inflator connections to the 7751 7753 module are shown in Figure 5 3 while dual stage inflator connections are shown in Figure 5 5 These connections accommodate all three tests for insulation resistance NOTE The interlock of the 7751 7753 must be enabled in order to use the V source Figure 5 6 shows how interlock is enabled 5 18 Model 2790 SourceMeter Switch System User s Manual Contact checks NOTE Low resistance 2 wire ohms measurement accuracy can be reduced by the resistance of the protective fuses on the 7751 7752 7753 modules which are in series with the DMM current source output See Fuse resistance consider ations page 6 2 for more information Test circuits The test circuits to verify contact are shown in Figure 5 9 single stage inflator and Figure 5 10 dual stage inflator Contact is checked by performing a continuity check through the V source test leads and the connection points Single stage inflator As shown in Figure 5 9 there are three contact connection points for the V source test circuit Contact checks are performed as follows e Bank 1 HI contact Close channels 1 14 and 18 to check the connection at
127. uard could float up to 500V WARNING Do not connect V source Hi to earth ground The 7751 7752 7753 mod ule uses a floating ground This floating ground is not connected to safety earth ground Not only will it create a shock hazard by floating up to 500V it will also effectively connect a 1nF capacitor across the V source providing energy storage that could ignite an airbag under fault conditions 4 10 Model 2790 SourceMeter Switch System User s Manual NOTE For high ohms measurements gt 1GQ it is recommended that the DUT be con nected between two different banks for example Bank I and Bank 3 as seen in test connection figures to reduce the possibility of measurement error caused by leakage resistance Switching module installation Module slot considerations Only one Model 7753 module can be installed in a Model 2790 and it should be installed in slot 1 A 7753 module can be used in slot 2 but measurement accuracy might be adversely affected because cards are always calibrated in slot 1 Power supply restrictions with the 7753 module Under some conditions low line maximum current draw two 7753 modules could draw enough power to cause the Model 2790 to reset To avoid this situation installed modules are checked at power up If a 7753 module is present the other slot must be empty or pop ulated with a 7702 module If this condition is violated a Model 7753 plus any other 775x module the Model 2790 will lock up
128. ule and one to calculate high resistance when using the V source and I V amplifier of a 7751 7753 module Low ohms calculation SxIohms e Sxlohms Calculates and displays low resistance reading for 7751 7752 7753 module in slot x where x 1 or 2 This ohms function is a shortcut for the mX b calculation When selected the following m and b factors are used m 1 Isour be Calculation R mX b 1 Isour X Vmeas 0 Vmeas ISOUR where Igoug is the programmed current level of the I source of the 7751 7752 or T133 1 Isoup is the m factor for the calculation mX b VmeEas IS the voltage measured by the DMM of the Model 2790 It is the X variable for the calculation mX b When the SxIohms calculation is selected the Model 2790 measures voltage X and calculates mX b using the above factors The displayed reading will be in ohms 2 This selection also sets DMM to DCV 1V range NOTE Sxlohms cannot be selected if the I source is set to OmA Since m 1 Isoup dividing I by 0 would result in an erroneous reading positive infinity When using the low ohms calculation the highest DCV measurement range that can be selected is 1 V Attempting to select a higher range will cause error 222 Parameter out of range Attempting to turn Autoranging on generates error 221 Settings conflict over the GPIB or a NO AUTORANGE message on the display if done from the front panel AUTO key
129. ure Coefficient Current Resistance Voltage Rdg Ohms 0 18 C amp 28 40 C 50mA 200 5 5V 0 09 40mO 0 002 3mQ C 20mA 500 5 5V 0 11 40mO 0 003 3mQ C 10mA 1000 5 5V 0 16 40mO 0 004 3 mQ C Dry Circuit Ohms ImA max with 7751 7752 or 7753 card ImA 10Q 20mV 1 10 40mO 0 026 3 mQ2 C 7751 Only Max Temperature Source Resistance Short Ckt Accuracy Coefficient Voltage Range Current Rdg 0 18 C amp 28 40 C 500V 10MQ lt ImA 0 8 0 03 C 500V 100MO mA 1 1 0 05 C 500V 1GO lt ImA 4 0 0 12 C 50V IMQ lt ImA 1 1 0 04 C 50V 10MQ lt ImA 1 1 0 06 C 50V 100MQ lt ImA 1 6 0 13 C 7753 Only Max Temperature Source Resistance Short Ckt Accuracy Coefficient Voltage Range Current Rdg 0 18 C amp 28 40 C 500V IMQ lt ImA 0 8 0 02 C 500V 10MQ lt ImA 0 9 0 03 C 500V 100MQ lt ImA 1 3 0 10 C 500V 1GO mA 6 7 0 27 C 50V 0 1MO lt ImA 1 1 0 03 C 50V IMQ lt ImA 1 1 0 04 C 50V 10MQ lt ImA 1 3 0 11 C 50V 100MQ lt ImA 4 5 0 30 C Current Source Output Output Level Programmable 0 to 50mA Ch 27 Programming Resolution 10uA Output Voltage 5 5V 10 compliance Accuracy 0 06 10uA 2 yr Specification Settling Time 1mS to 0 1 of final value typ Temperature Coefficient 0 18 C amp 28 40 C 0 001 0 25uA C Dry Circuit Clamp Ch 24 20mV 10 Isource lt ImA Voltage Source Output 7751 7753 Only Output Level Programmabl
130. ween any two Terminals gt 1GQ 100pF Isolation Between Terminals and Earth gt 1GQ lt 200pF Isolation Between Channel Groups gt 500GQ 100pF External Common Mode Voltage 42V between any terminal and chassis Connect no external sources 7751 7752 or 7753 Module Notes Tsolation for channels 1 12 only one channel closed at a time or all channels open See User s manual for ohm specifications at sources other than those specified All specifications valid for 1 NPLC ADC aperture setting System Throughput Connect source measure calculate 0 01 NPLC Filter Off over GPIB Bus High Ohms Source V 13 Rdgs Sec Low Ohms Source I 9 Rdgs Sec NPLC Filter On Over GPIB Bus High Ohms Source V 11 Rdgs Sec Low Ohms Source I 7 Rdgs Sec System Throughput Notes 1 Reset upon fixed Vsource level no settling time HW 11 04 03 Rev D 2790 SourceMeter Switch System Specifications 7751 7752 7753 SOURCE SWITCH MODULE SPECIFICATIONS Ch 1 Sense J101 Source LO Ch 2 Sense A10 of c Ch 3 B1 o o Source 0 o o HI Bank 1 Source O O1 O HI Ch 4 Bank 2 Sense J102 Source LO Ch 5 Sense A2 i Ch 6 B2 0 o c Source 0 0 o HI Ch 7 Bank 3 Sense J103 Source 0 0o O L O Ch 8 Sense A3 o of Ch 9 B3 o o c Source 0 o o HI Ch 10 B
131. will automatically be inspected for PASS FAIL conditions Digital outputs corresponding to these conditions are also available NOTE Memory patterns can be used only with the following functions DC volts 2 wire ohms and 4 wire ohms Front panel operation Memory patterns cannot be defined from the front panel but they can be recalled once defined by remote commands see below To recall defined memory patterns from the front panel 1 Press CLOSE 2 Usethe RANGE A and keys to select CLOSE MEMORY then press ENTER 3 Use lt q gt A and to select the memory pattern number 1 40 then press ENTER Model 2790 SourceMeter Switch System User s Manual 2 21 Memory pattern commands Memory patterns commands are summarized in Table 2 5 See Section 2 of the Model 2790 Reference Manual for details on these commands ROUTe MEMory CHANnels n lt clist gt Create channel pattern for memory n 1 40 Note 7702 channels cannot be included in lt clist gt ROUTe MEMory SOURce LEVel n lt NRf gt lt clist gt Assign source values to the channels in lt clist gt that will be output when memory pattern lt n gt is executed Source channels only 127 128 227 or 228 ROUTe MEMory DELay lt n gt lt NRf gt Assign a variable delay to memory pattern lt n gt Time in seconds after closing channels and setting source values before making measurements ROUTe MEMory RECall lt n gt Immedia

Model 2790 Sourcemeter Switch system User`s Manual

Contents

Download Pdf Manuals

Related Search

Related Contents