Keithley 7708 User Manual
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Keithley 7708 User Manual

Keithley 7708 User Manual

40-channel differential multiplexer with automatic cjc
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Model 7708
40-Channel Differential Multiplexer
with Automatic CJC
User's Guide
PA-744 Rev. C / 8-03
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 7708

  • Page 1 Model 7708 40-Channel Differential Multiplexer with Automatic CJC User’s Guide PA-744 Rev. C / 8-03 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 WARRANTY Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year from date of shipment. Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batteries, diskettes, and documentation.

  • Page 3: Safety Precautions

    Keithley products are designed for use with electrical signals that The instrument and accessories must be used in accordance with its are rated Measurement Category I and Measurement Category II, as specifications and operating instructions or the safety of the equip-...
  • Page 4 Keithley Instru- symbol on an instrument indicates that the user should re- ments. Standard fuses, with applicable national safety approvals, fer to the operating instructions located in the manual.

  • Page 5: Table Of Contents

    Fax: (440) 248-6168 www.keithley.com Introduction The Model 7708 is a 40-channel differential multiplexer card with the following features: • DC and AC voltage measurement • 2-wire or 4-wire Ω measurement (automatically pairs switches for four wire measurements — n + 20) •...

  • Page 6: Specifications

    Making amps measurements – In order to perform amps measurements, you must use the front panel inputs of the 27xx main- frame. You can still use the 7708 module for other aspects of the test (such as controlling a bias supply for DUT), but you must use multiple channel operation to close channels.

  • Page 7: Description

    Although the Model 7708 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.

  • Page 8: Card Connections

    The information in this section is intended for qualified service personnel. Do not attempt to perform this procedure unless qualified to do so. Figure 2 shows how to access the screw terminals on the Model 7708. Channel designations for the screw terminals are contained in Figure WARNING Do not exceed the maximum specifications for the Model 7708 module.
  • Page 9 Figure 3 Model 7708 screw terminal channel designations Cable tie holes CH10 CH11 CH12 CH13 CH14 Cable tie holes...

  • Page 10: Wiring Procedure

    Use the following procedure to wire the Model 7708 module. Make all connections using the correct wire size (up to 20 AWG). Also, make sure to add supplementary insulation around the harness for voltages above 42V peak (see...

  • Page 11: Typical Connections

    Typical connections The following examples show typical wiring connections for the following types of measurements: • Thermocouple connections, see Figure 5 • Ω2-wire and thermistor connections, see Figure 6 • Ω4-wire and RTD connections, see Figure 7 • Voltage (AC or DC), see Figure 8 Figure 5 Thermocouple connections...
  • Page 12 Figure 7 Ω 4-wire and RTD connections Resistor or Channel 1 4-Wire RTD (Channels 2–19) Resistor or Channel 20 4-Wire RTD Channel 21 (Channels 22–39) Channel 40 Figure 8 Voltage connections (DC or AC) Channel 1 DC Voltage AC Voltage (Channels 2–39) Channel 40...

  • Page 13: Connection Log

    Connection log Make a copy of Table 1 and affix it to the cover of the Model 7708. Use this to record connection information and channel descriptions as needed. Table 1 Connection log Model 7708 Channel Color Description Description Color...

  • Page 14: Performance Verification

    Performance verification The performance of the Model 7708 card is tested by verifying measurement accuracy through the card. If verification limits are met through the front panel terminals of the Model 27xx, they should also be met through the card.

  • Page 15: Test Considerations

    INPUTs switch In order to connect the Model 7708 card to the meter of the Model 27xx, the INPUTs switch must be in the REAR (in) position. The INPUTS switch is located on the front panel of the Model 27xx multimeter near the input terminals.

  • Page 16: Recommended Test Equipment

    100M Ω :±120ppm Fluke 5725A Amplifier: AC Voltage, 50kHz: 700V, ±375ppm Keithley 3930A or 3940 Frequency Synthesizer: 1V RMS, 10V RMS, 1kHz, ±5ppm, steady state and burst modulation General Radio 1433-T Precision Decade Resistance Box: 10 Ω to 400 Ω , ±0.02%...

  • Page 17: Performance Verification Procedures

    Model 7708 2. Install the Model 7708 in Slot 1 of the Model 27xx, turn on the power, and allow the unit to warm up for two hours before proceeding. Be sure the front panel INPUTS switch is set to the REAR position.
  • Page 18 Figure 2. Install the Model 7708 in Slot 1 of the Model 27xx, turn on the power, and allow the unit to warm up for two hours before proceeding. Be sure the front panel INPUTS switch is set to the REAR position.
  • Page 19 CH13 CH14 CH10 CH11 Model 7708 4. Set the Model 27xx for the 100mV range; make sure that REL is disabled. 5. Source 1kHz and 50kHz AC voltages for each of the ranges summarized in Table 4, and make sure that the respective Model 27xx readings fall within stated limits.
  • Page 20 Figure 2. Install the Model 7708 in Slot 1 of the Model 27xx, turn on the power, and allow the unit to warm up for two hours before proceeding. Be sure the front panel INPUTS switch is set to the REAR position.
  • Page 21 5. Set the Model 27xx for the 100Ω range, and make sure the FILTER is on. Enable OCOMP (offset-compensated ohms) for the 100Ω range test. (Press SHIFT then OCOMP.) 6. Recalculate reading limits based on actual calibrator resistance values. 7. Source the nominal full-scale resistance values for the 100Ω-10MΩ ranges summarized in Table 5, and verify that the readings are within calculated limits.
  • Page 22 8. Connect the Model 7708 CH1 and CH21 terminals to the calibrator as shown in Figure 9. Disable external sense on the calibrator. 10. Set the Model 27xx for the 100MΩ range. 11. Source a nominal 100MΩ resistance value, and verify that the reading is within calculated limits for the 100MΩ range.
  • Page 23 Figure 2. Install the Model 7708 in Slot 1 of the Model 27xx, turn on the power, and allow the unit to warm up for two hours before proceeding. Be sure the front panel INPUTS switch is set to the REAR position.
  • Page 24 2. Install the Model 7708 in Slot 1 of the Model 27xx, turn on the power, and allow the unit to warm up for two hours before proceeding. Be sure the front panel INPUTS switch is set to the REAR position.
  • Page 25 14.) 2. Install the Model 7708 in Slot 1 of the Model 27xx, then turn on the power, and allow the unit to warm up for one hour before proceeding. Be sure the front panel INPUTS switch is set to the REAR position.
  • Page 26 Figure 2. Install the Model 7708 in Slot 1 of the Model 27xx, turn on the power, and allow the unit to warm up for two hours before proceeding. Be sure the front panel INPUTS switch is set to the REAR position.

  • Page 27: Calibration

    2. With the power off, install the Model 7708/7797 combination in Slot 1 and select the rear inputs with the INPUTS switch. Allow three minutes for thermal equilibrium. 3. Accurately measure and record the cold temperature of the Model 7708 card surface at the center of the card with a digital thermometer.

  • Page 28: Replaceable Parts

    1. Connect the Model 7708 to the 7797 Calibration/Extender Board (see “Extender board connections” above). 2. With the power off, install the Model 7708/7797 combination in Slot 1, and select the rear inputs with the INPUTS switch. Allow three minutes for thermal equilibrium.
  • Page 29 Table 9 Model 7708 parts list Circuit Designation Description Keithley Part No. C1, C3, C4, C7, C9-C11, C14, C200, C201, CAP, 0.1µF, 20%, 50V, CERAMIC C-418-.1 C203-C213 C2, C6, C17-C20, C23-C25, C202 CAP, 47pF, 5%, 100V, CERAMIC C-465-47P CAP, 4.7µF, 10%, 35V, TANTALUM C-476-4.7...

  • Page 30: Ordering Information

    Ordering information To place an order, or to obtain information concerning replacement parts, contact your Keithley representative or the factory (see inside front cover for addresses). When ordering parts, be sure to include the following information: • Card model number (Model 7708) •...
  • Page 31 7708 40-Channel Differential Multiplexer w/Automatic CJC GENERAL 40 CHANNELS: 40 channels of 2-pole relay input. All channels configur- Card Input able to 4-pole. RELAY TYPE: Latching electromechanical. ACTUATION TIME: <3ms. Card Sense Specified for Model 2700, firmware revision BO2 or later.
  • Page 34 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. Keithley Instruments, Inc. 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: 440-248-6168 1-888-KEITHLEY (534-8453) •...

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