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Keithley 2790 User Manual

Sourcemeter switch system
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Model 2790
®
SourceMeter
Switch System
User's Manual
A G R E A T E R M E A S U R E O F C O N F I D E N C E

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Summary of Contents for Keithley 2790

  • Page 1 Model 2790 ® SourceMeter Switch System User’s Manual A G R E A T E R M E A S U R E O F C O N F I D E N C E...
  • Page 2 ® 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...
  • Page 3 Revision B (Document Number 2790-900-01) ............. March 2002 Revision C (Document Number 2790-900-01) ............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.
  • Page 4 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.
  • Page 5 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 if the rating and type are the same. Other components that are not safety related may be purchased from other suppliers as long as they are equivalent to the original component.

  • Page 6: Table Of Contents

    Shunt bar test ............... Bridgewire test ..............Insulation resistance (HIPOT) test (7751 and 7753 only) .. Keithley 7751, 7752, and 7753 Switching Modules Card configuration ..............I-source – channels 21, 22, 24, and 27 ........ V-source and I/V amplifier (7751/7753 only) –...
  • Page 7 Keithley 7702 Switching Module Safety precautions ..............Card configuration ..............Typical connections ..............Connection log ..............Opening and closing 7702 channels ........... Channel assignments ............Front panel operation ............3-10 Remote programming ............3-11 Viewing closed channels ............3-12 Using 7751/7753 V-source with 7702 module ......
  • Page 8 High ohms measurements ........... 4-wire ohms ................Offset compensated ohms ............Keithley 7702 module ..............Keithley 7751, 7752, and 7753 modules ........Specifications (Models 2790, 7751, 7752, 7753, and 7702) ......Ohms specification calculations (7751/7752/7753) ....7751/7752/7753 I-source ........... 7751/7753 V-source ............
  • Page 9 Bridgewire testing ..............Figure 1-4 HIPOT testing (7751/7753) ........... Keithley 7751, 7752, and 7753 Switching Modules Figure 2-1 Simplified schematic of Keithley 7751, 7752, and 7753 switching modules ............Figure 2-2 Setting I-source and V-source output levels ......Figure 2-3 Enabling ohms math function ..........
  • Page 10 Using W2 function to measure resistance ......Figure 6-2 Using W4 function to measure resistance ......Figure 6-3 Using Model 2790 4-wire ohms with 7702 module (low ohms measurements) ..........Figure 6-4 Using Model 2790 2-wire ohms with 7702 module (high ohms measurements) ..........
  • Page 11 List of Tables Keithley 7751, 7752, and 7753 Switching Modules Table 2-1 Commands to set amplitude for V-source and I-source ..Table 2-2 Commands to select ohms calculations ....... 2-12 Table 2-3 Commands to control 7751/7752/7753 module channels ..2-14 Table 2-4 Connection log Model 7751/7752/7753 ......

  • Page 12: Test System Overview

    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.

  • Page 13: Introduction

    Switch System User’s Manual Introduction 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.

  • Page 14: Technical Terms

    ® Model 2790 SourceMeter Switch System User’s Manual 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”...

  • Page 15: Model 2790 Configurations

    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.

  • Page 16: 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.

  • Page 17: Inflator Tests

    7751/7752/7753 clamps voltage at 20mV (1mA maximum) 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 R reading can be read directly from the dis- SHUNT play of the Model 2790.

  • Page 18: Figure 1-2 Shunt Bar Testing

    50mA. An even more accurate resistance measurement can be achieved using the Ω4 function of the Model 2790. Keep in mind that this is an additional test and does not replace the test using the dry circuit.

  • Page 19: Bridgewire Test

    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 Keithley 2790 SourceMeter Switch System...

  • Page 20: Insulation Resistance (Hipot) Test (7751 And 7753 Only)

    DMM of the Model 2790. NOTE If not using a 7751/7753 module in your test system, resistance up to 120MΩ can be measured using the Ω2 function of the Model 2790. Figure 1-4 HIPOT testing (7751/7753) Keithley 2790 SourceMeter Switch System Keithley 7751/7753 Module –...
  • Page 21 The resistance reading for a contact should be less than 20 ohms (depending on cabling). 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.

  • Page 22: Keithley 7751, 7752, And 7753 Switching Modules

    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. • Setting source output levels — Explains how to set the output levels for the I-source (7751/7752/7753) and V-source (7751/7753).

  • Page 23: Card Configuration

    ® Model 2790 SourceMeter Switch System User’s Manual NOTE Module wiring and installation into the mainframe of the Model 2790 is covered Section Details on using the Keithley 7751, 7752, 7753 modules to test inflators are provided in Section The edit keys (left, right, up, and down arrow keys) are used to display menu items and output levels.

  • Page 24: Figure 2-1 Simplified Schematic Of Keithley 7751, 7752, And 7753 Switching Modules

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 2-1 Simplified schematic of Keithley 7751, 7752, and 7753 switching modules Ch. 25 Ch. 13 Source Ch. 14 Ch. 1 Sense Bank 1 J101 Source Ch. 2 Ch. 15 Sense Ch. 3 Ch.

  • Page 25: I-Source - Channels 21, 22, 24, And 27

    ® 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 current to measure low resis- tance (inflator bridgewires and shunt bars). • The I-source is designated as channel 27.

  • Page 26: Source Readback - Channels 13 And 25

    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 •...

  • Page 27: Safety Warnings

    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 Model 2790 or through a 7702 module, these safety features are compromised, creat- ing the very real possibility of igniting the airbag.

  • Page 28: Figure 2-2 Setting I-Source And V-Source Output Levels

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 2-2 Setting I-source and V-source output levels Press SHIFT Press CARD Select CONFIG 77xx =7751/7752/7753 SLOT2: 77xx SLOT1: 77xx Select module 7751 7751 Set I-source 7752 I-C27:01.00 mA I-C27:01.00 mA 7752...

  • Page 29: Remote Programming

    ® 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.

  • Page 30: Math

    1 / I is the “m” factor for the calculation (mX+b). SOUR is the voltage measured by the DMM of the Model 2790. It is the “X” MEAS 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.
  • Page 31 MEAS 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 (Ω). This selection also sets DMM to DCV, 10V range.

  • Page 32: Front Panel Operation

    “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.

  • Page 33: Table 2-2 Commands To Select Ohms Calculations

    ® 2-12 Model 2790 SourceMeter Switch System User’s Manual Table 2-2 Commands to select ohms calculations Commands Description Default CALCulate[1]:FORMat <name> Select math function: NONE, MXB, PERC PERCent, RECiprocal, S1Iohms, S1Vohms, S2Iohms, S2Vohms. CALCulate[1]:FORMat? Query selected math format. CALCulate[1]:STATe <b>...

  • Page 34: Opening And Closing Channels

    You must explicitly close them to perform a measurement. For example, with a DUT connected to channel 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. •...

  • Page 35: Remote Programming

    ® 2-14 Model 2790 SourceMeter Switch System User’s Manual Figure 2-4 Opening and closing channels A) Opening one or all channels Press OPEN key OPEN CLOSE Display ALL option Display MULT option OPEN: MULT OPEN: ALL and press OPEN again...

  • Page 36: Viewing 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 releasing SHIFT and then pressing CARD. As shown in...

  • Page 37: Open Interlock Errors

    +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...

  • Page 38: Cable Discharge Circuit (7751 And 7753)

    ® 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 high enough to store a high voltage charge from the V-source of the 7751/7753 module.

  • Page 39: Figure 2-6 Cable Discharge Circuit

    ® 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.

  • Page 40: Connection Log

    ® Model 2790 SourceMeter Switch System User’s Manual 2-19 Connection log 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...

  • Page 41: Using Memory Patterns

    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...

  • Page 42: Memory Pattern Commands

    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. Command Description :ROUTe:MEMory[:CHANnels] <n>, <clist> Create channel pattern for memory <n> (1-40). Note: 7702 channels cannot be included in <clist>.

  • Page 43: Memory Pattern Command Options

    Memory pattern command options All CALCulate, SENSe, and UNIT subsystem commands with a <clist> (channel list) parameter associated with Model 2790 DC volts, 2-wire ohms, and 4-wire ohms measure- ment functions can include a memory pattern <clist> parameter (@Mn) that allows you to assign those functions to specific memory pattern locations.

  • Page 44: Memory Pattern Log

    ® 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...
  • Page 45 ® 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...

  • Page 46: Keithley 7702 Switching Module

    7751/7753 V-source with the 7702 module. Includes a test circuit diagram to explain this application. • 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.

  • Page 47: Safety Precautions

    Section 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 The edit keys (left, right, up, and down arrow keys) are used to display menu items and output levels.

  • Page 48: 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.

  • Page 49: Figure 3-1 Simplified Schematic Of Keithley 7702 Switching Module

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 3-1 Simplified schematic of Keithley 7702 switching module Input Sense Channel 1 Channel 45 (see Note) (Channels 2–19) Backplane Isolation Channel 20 Input Channel 43 2-Pole (Open) Channel 44 4-Pole (Closed)

  • Page 50: Typical Connections

    ® Model 2790 SourceMeter Switch System User’s Manual Typical connections The following examples show typical 7702 wiring connections for the following types of measurements: Ω • 2 and thermistor temperature connections, see Figure 3-2. Ω • 4 and RTD temperature connections, see Figure 3-3.

  • Page 51: Figure 3-4 Current Connections (Dci And Aci)

    4-Wire RTD Channel 21 (Channels 22–39) 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) 7702 Channel 41 Channel 42...

  • Page 52: Connection Log

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 3-5 Voltage connections (DCV or ACV) DC Voltage AC Voltage 7702 Channel 1 (Channels 2–39) Channel 40 Connection log Make a copy of Table 3-1 and affix it to the cover of the Model 7702. Use this to record...

  • Page 53: Table 3-1 Connection Log Model 7702

    ® Model 2790 SourceMeter Switch System User’s Manual Table 3-1 Connection log Model 7702 Channel Color Description Description Color Channel INPUT SENSE CH21 CH22 CH23 CH24 CH25 CH26 CH27 CH28 CH29 CH30 CH10 CH31 CH11 CH32 CH12 CH33 CH13 CH34...

  • Page 54: Opening And Closing 7702 Channels

    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. •...

  • Page 55: Front Panel Operation

    ® 3-10 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 keys or the SINGLE option for the CLOSE key. The OPEN:ALL option for the OPEN key opens all channels.

  • Page 56: Remote Programming

    ® Model 2790 SourceMeter Switch System User’s Manual 3-11 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 For a 7751/7752/7753 module, the OPEN:ALL operation will not open channel 20 if the interlock is open.

  • Page 57: Viewing Closed Channels

    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? <clist>. (See Table 2-2 in the Model 2790 Reference Manual.) Figure 3-9 Viewing closed channels Press SHIFT...

  • Page 58: Using 7751/7753 V-Source With 7702 Module

    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.
  • Page 59 ® 3-14 Model 2790 SourceMeter Switch System User’s Manual Figure 3-10 Using 7751/7753 V-source with 7702 module (dual multiplexer) Model 2790 Keithley 7751/7753 Module Vsrc HI All 7751/7753 channels open J107 SOURCE Vsrc LO Keithley 7702 Module Sense Ch 1...

  • Page 60: 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.

  • Page 61: Connections And Wiring

    ® Model 2790 SourceMeter Switch System User’s Manual Connections and wiring WARNING The following information is intended for qualified service personnel. Do not make switching module connections unless qualified to do so. WARNING To prevent electric shock that could result in serious injury or death, adhere to following safety precautions: •...

  • Page 62: Cabling Requirements

    ® Model 2790 SourceMeter Switch System User’s Manual 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.

  • Page 63: Wiring Procedure

    ® 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).

  • Page 64: Figure 4-2 Model 7751/7752/7753 Screw Terminal Channel Designations

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 4-2 Model 7751/7752/7753 screw terminal channel designations J101 (Input channels 1-3) J102 (Input channels 4-6) BANK 1 BANK 2 Ch 3 Ch 4 Ch 5 Ch 6 Ch 1 Ch 2...

  • Page 65: Figure 4-3 Model 7702 Screw Terminal Channel Designations

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 4-3 Model 7702 screw terminal channel designations CH10 CH14 CH12 CH16 CH18 CH13 CH17 CH11 CH15 CH19 CH20 TE122 TE121 CH21 CH40 CH22 CH26 CH39 CH28 CH30 CH32 CH24 CH34 CH36...

  • Page 66: Figure 4-4 Wire Dressing (7751/7752/7753)

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 4-4 Wire dressing (7751/7752/7753) BANK 1 Ch 1 Ch 2 Cable Tie Supplementary Insulation BANK 1 SOURCE SENSE GUARD BANK 2 ® Zippertubing Shield Ground Cable Tie Wire BANK 4 I / V...

  • Page 67: Zippertubing® Shield

    ® 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.

  • Page 68: Guarding

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 4-6 ® Installed Zippertubing shield Test BANK 1 SOURCE SENSE GUARD Station BANK 2 Keithley Switching Module Ground wrapped cable bundle BANK 4 I / V INTERLOCK VSOURCE ISOURCE GUARD I / V...

  • Page 69: Switching Module Installation

    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.

  • Page 70: Inflator Testing

    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.

  • Page 71: Introduction

    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. 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 —...

  • Page 72: Closed Channels For Test Circuits

    2. If using a PC, select the GPIB interface and set the address of the 2790. 3. Use a cable terminated with a female DB-9 connector to mate to the DIGITAL I/O connector of the 2790. 4. Cable must be wired as a straight-through cable (not null modem cable).

  • Page 73: Interface (Plc Or Pc)

    Model 2790 SourceMeter Switch System User’s Manual RS-232 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: • Baud rate: 19.2K, 9600, 4800, 2400, 1200, 600, or 300...

  • Page 74: Test Signal Connections

    5-5. Single stage inflator test connections: • 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 —...

  • Page 75: Figure 5-3 Test Connections – Shunt Bar, Hipot, And Bridgewire Testing – Single Stage Inflator

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 5-3 Test connections – shunt bar, HIPOT, and bridgewire testing – single stage inflator Single Stage Inflator A) Shunt Bar and B) Bridgewire Testing Keithley 7751/7753 HIPOT Testing Bank 1 J101...

  • Page 76: Figure 5-4 Test Connections – Shunt Bar And Bridgewire Bar Testing – Dual Stage Inflator

    Switch System User’s Manual 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 —...

  • Page 77: Figure 5-5 Test Connections – Shunt Bar, Hipot, And Bridgewire Testing – Dual Stage Inflator

    ® Model 2790 SourceMeter Switch System User’s Manual Figure 5-5 Test connections – shunt bar, HIPOT, and bridgewire testing – dual stage inflator Dual Stage Inflator A) Shunt Bar and B) Bridgewire Testing HIPOT Testing Keithley 7751/7753 Bank 1 J101...

  • Page 78: Interlock

    — 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 Keithley 7751, 7752, or 7753 J106 Test Station INTERLOCK Connect to safety earth INTERLOCK ground using #18 AWG wire or larger.

  • Page 79: Shunt Bar Test

    Channel 21 — With this channel open, the selected source is isolated from the rest of the module. • Channels 18 and 19 — With these channels open, the backplane of the Model 2790 is isolated from the switching module. Open interlock errors...

  • Page 80: 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. Figure 5-7 Test circuit – shunt bar Keithley 7751, 7752, or 7753 MEAS SHUNT SOUR 1 or 4* 1 or 4* 1Ω...

  • Page 81: Test Procedure

    ® 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.

  • Page 82: Table 5-1 Test Procedure – Shunt Bar

    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.

  • Page 83: Bridgewire Tests

    Test circuit The circuit for an inflator bridgewire test is shown in Figure 5-8. Figure 5-8 Test circuit – bridgewire tests Keithley 7751, 7752, or 7753 1 or 4* 1 or 4* 1Ω Input HI Bridgewire Under...

  • Page 84: Test Procedure

    Table 5-2 Test procedure – bridgewire Test Step Command Sequence Front Panel Operation *RST 1) Reset 2790 and Press SHIFT > press SETUP > select RESTORE: open all channels. FACT. SOUR:CURR 0.05,(@127) 2) Set I-source to Press SHIFT > press CARD > select CONFIG >...

  • Page 85: I-Source Readback

    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.

  • Page 86: Insulation Resistance (Hipot) Tests (7751/7753 Only)

    There are three basic tests for insulation resistance. Two preliminary verification tests and the HIPOT test. • 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.

  • Page 87: Contact Checks

    ® 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-...

  • Page 88: Figure 5-9 Test Circuits - Contact Check - Single Stage Inflator

    ® Model 2790 SourceMeter Switch System User’s Manual 5-19 Figure 5-9 Test circuits – contact check – single stage inflator Internal 0.062A Keithley 7751/7753 fuses not shown (see Section 6) Contact Point 2790 Ω2 Bank 1 (1 of 2) Single Stage 2790 Ω2...

  • Page 89: Table 5-3 Test Procedure – Contact Checks For Single Stage Inflator

    1. 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.

  • Page 90: Table 5-4 Test Procedure – Contact Checks For Dual Stage Inflator

    Test step notes: 1. 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.

  • Page 91: V-Source Readback

    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...

  • Page 92: Cable Discharge

    Test step notes: 1. 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.

  • Page 93: Hipot Test

    ® 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...

  • Page 94: Figure 5-12 Test Circuit - Hipot

    ® Model 2790 SourceMeter Switch System User’s Manual 5-25 Figure 5-12 Test circuit – HIPOT Inflator Keithley 7751/7753 Inflator Housing 1 or 4* Shunt 3 and 6* Bridgewire SOUR = – Internal HIPOT shunts MEAS 1Ω 500V Leakage = –...

  • Page 95: Test Procedure - Hipot

    Table 5-6 Test procedure – HIPOT Test Step Command Sequence Front Panel Operation *RST 1) Reset 2790 and Press SHIFT > press SETUP > select RESTORE: open all channels. FACT. SOUR:VOLT 500,(@128) 2) Set V-source to Press SHIFT > press CARD > select CONFIG >...
  • Page 96 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.

  • Page 97: I-Source Readback

    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 1Ω resistor ). Readback current (I ) is then calculated using Ohms Law (I / 1Ω).

  • Page 98: Figure 5-13 I-Source Readback Circuit

    ® 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 MEAS Input LO Input HI 1Ω Keithley 7751, 7752, or 7753 1 or 4* 1Ω Bridgewire...

  • Page 99: Memory Patterns Test

    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...

  • Page 100: Test Procedure

    ® Model 2790 SourceMeter Switch System User’s Manual 5-31 Test procedure 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...
  • Page 101 ® 5-32 Model 2790 SourceMeter Switch System User’s Manual Table 5-7 (cont.) Command sequence for memory patterns test example using scanning Command Sequence Description Set up memory location 3: ROUT:MEM:CHAN 3,(@108,115,118) Set channels 8, 15, and 18 for memory location 3.

  • Page 102: Table 5-8 Command Sequence For Memory Patterns Test Example Using Individual Memory Pattern Recall

    ® Model 2790 SourceMeter Switch System User’s Manual 5-33 Table 5-8 Command sequence for memory patterns test example using individual memory pattern recall Command Sequence Description *RST Restore GPIB defaults. ROUT:MEM:CLE:ALL Clear all memory pattern locations. Set up memory location 1: ROUT:MEM:CHAN 1,(@101,114,118) Set channels 1, 14, and 18 for memory location 1.
  • Page 103 ® 5-34 Model 2790 SourceMeter Switch System User’s Manual...

  • Page 104: Model 2790 Dmm Ohms Functions

    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 7751/7752/7753 module.

  • Page 105: Introduction

    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 100Ω and 1kΩ ranges, the test current is fixed at 1mA.

  • Page 106: High Ohms Measurements

    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 Ω2 function (100MΩ range) of the Model 2790 to measure insulation resistance up to 120MΩ. 4-wire ohms 4-wire ohms eliminates the effects of test lead resistance when measuring a low ohms DUT.
  • Page 107 (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...

  • Page 108: Offset Compensated Ohms

    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 100Ω, 1kΩ, and 10kΩ...

  • Page 109: Keithley 7702 Module

    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).
  • Page 110 Switch System User’s Manual Figure 6-4 shows the simplified test circuit for using the Ω2 function of the Model 2790 with the 7702 module to measure high ohm DUT (i.e., insulation resistance) up to 120MΩ. 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.

  • Page 111: Keithley 7751, 7752, And 7753 Modules

    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 voltage across the DUT is not sensed through the fuse resistance (see “Fuse resistance...

  • Page 112: Figure 6-6 Using Model 2790 2-Wire Ohms With 7751/7752/7753 Module (High Ohms Measurements)

    120MΩ. 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.
  • Page 113 ® 6-10 Model 2790 SourceMeter Switch System User’s Manual...

  • Page 114: Specifications

    (Models 2790, 7751, 7752, 7753, and 7702) • 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. • Ohms specification calculations (7751/7752/7753) — Provides equations to calculate ohms specifications for source levels not specified in the 7751/7752/7753...
  • Page 115 2790 SourceMeter Switch System Specifications 7751/7752/7753 SOURCE/SWITCH MODULE SPECIFICATIONS Accuracy: 0.5% + 0.13V (2yr Specification). 2790 Resistance Mode Specifications with Cards Settling Time: Rise Time: 50V to 500V step, 0.1% of final value, 250 ms max. (Module function accuracy specifications are for 2 years, Fall Time: 500V to 50V step, 0.1% of final value,...
  • Page 116  2790 SourceMeter Switch System Specifications 7751/7752/7753 SOURCE/SWITCH MODULE SPECIFICATIONS Ch. 25 Ch. 13 Ch. 14 Source Ch. 1 Sense Bank 1 Ch. 15 J101 Source Ch. 2 Sense Ch. 16 Ch. 18 Input To Model 2790 Ch. 3 Backplane Ch.
  • Page 117  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 ACCURACY: ±(ppm of reading + ppm of range) or MED (1 PLC) with Digital Filter of 10 (ppm = parts per million) (e.g., 10ppm = 0.001%)
  • Page 118  2790 SourceMeter Switch System Specifications MAINFRAME FUNCTION SPECIFICATION 14, 17 DC System Speeds DC Notes 20% overrange except on 1000V and 3A. RANGE CHANGES : 50/s (42/s). Add the following to “ppm of range” uncertainty; 100mV 15ppm, 1V FUNCTION CHANGES : 50/s (42/s).
  • Page 119  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- 50 kHz- 100 kHz- Function Range Resolution...
  • Page 120  2790 SourceMeter Switch System Specifications MAINFRAME FUNCTION SPECIFICATION GENERAL SPECIFICATIONS 7, 11 AC System Speeds POWER SUPPLY: 100V / 120V / 220V / 240V. RANGE CHANGES : 4/s (3/s). LINE FREQUENCY: 50Hz to 60Hz and 400Hz, FUNCTION CHANGES : 4/s (3/s).

  • Page 121: Ohms Specification Calculations (7751/7752/7753

    I-source settings: NOTE The following formulas are only valid when using 1VDC range of the Model 2790 DMM. When using the SIxOhms math calculation, the 1V range is selected automatically. Ohms accuracy % of reading = (0.07 + 1/I SOURCE Ohms offset = (0.03/I...

  • Page 122: 7751/7753 V-Source

    ® Model 2790 SourceMeter Switch System User’s Manual Specifications Ohms temperature coefficient TC % of reading = (0.001 + 0.025/I ) % / °C SOURCE TC ohms offset = (0.001/I ) Ω / °C SOURCE where; I is the current output setting in mA SOURCE Example –...
  • Page 123 ® A-10 Specifications Model 2790 SourceMeter Switch System User’s Manual Ohms temperature coefficient TC % of reading = (0.02 + 1/V ) % / °C SOURCE TC ohms offset = 200Ω Ω Ω Ω / °C where; V is the voltage output setting in volts SOURCE Example –...
  • Page 124 ® Model 2790 SourceMeter Switch System User’s Manual Specifications A-11 For measurements 100MΩ Ω Ω Ω to 1GΩ Ω Ω Ω Ohms accuracy % of reading = (2 + 510/V SOURCE Ohms offset = 20kΩ Ω Ω Ω where; V...
  • Page 125 ® A-12 Specifications Model 2790 SourceMeter Switch System User’s Manual...
  • Page 126 Index Front Panel 3-10 Open interlock errors 5-10 operation 2-11 message 2-16 airbag inflators opening and closing channels 2-13 view closed channels 2-15 remote programming test procedures Bridgewire test test procedure bus programming 2-8, 2-11 bridgewire 5-15 contact checks 5-20, 5-21, 5-31, 5-33 Cable discharge HIPOT...
  • Page 127 Manual cable discharge 2-18 Math Power 4-10 matrix backplane and guard terminals primary tests Memory 2-21, 2-22, 2-23, 5-30 programmable memory 2-20 logic controller Memory patterns, setting up 2-21 voltage source Model 7700, 7702, and 7703 Programming errors 2-12 Introduction Model 7702 Ω2-Wire and Thermistor connections quick-disconnect terminal blocks...
  • Page 128 Test circuit – shunt bar 5-11 Test configurations Test connections shunt bar and bridgewire shunt bar, HIPOT and bridgewire Test System Overview testing two inflators Typical connections Model 7702 typical test system Viewing closed channels Model 7702 3-12 Model 7751/7752 2-15 V-source and I/V amplifier...
  • Page 130 A G R E A T E R M E A S U R E O F C O N F I D E N C E Keithley Instruments, Inc. Corporate Headquarters • 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: 440-248-6168 • 1-888-KEITHLEY (534-8453) • www.keithley.com •...

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