Tektronix Keithley 7706 User manual

Keithley Instruments
28775 Aurora Road
Cleveland, Ohio 44139
1-800-935-5595
tek.com/keithley
Model 7706 Multiplexer Module
Instructions for use with DAQ6510
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Introduction
The 7706 20-Channel Differential Multiplexer switching module offers 20 channels of 2-pole or 10 channels of
4-pole multiplexer switching with automatic CJC. It also offers two analog output channels, 16 digital outputs,
and one event counter/totalizer. You can use the event counter/totalizer to monitor and control system
components while making mixed signal measurements. The 7706 is ideal for RTD, thermistor, and
thermocouple temperature applications.
Figure 1: 7706 Multiplexer Module
Item shipped may vary from model pictured here.

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The 7706 includes the following features:
▪Twenty channels of analog input with 300 V,1 A capacity; 60 W, 125 VA maximum
▪Sixteen channels of digital output
▪One event counter/totalizer, which you can use to monitor and control system components and actions,
such as fixtures, limit switches, pass/fail indicators, external voltage sources, loads, door closures, and
revolutions
▪Two analog outputs (±12 V at 5 mA with 16-bit programmability)
▪Two-wire or four-wire resistance measurements (automatically pairs switches for four-wire measurements)
▪Built-in automatic cold junction reference (CJC)
▪Screw terminal connections
The 7706 can be used with the DAQ6510 Data Acquisition and Multimeter System.
If you are using this switching module with the 2700, 2701, or 2750, please see Model 7706
Multiplexer Card User's Manual, Keithley Instruments document PA-719.
Wiring procedure
Use the following procedure to make connections to the 7706 module. Make all connections using correct wire
size (up to 22 AWG).
Connection and wiring procedures in this document are intended for use by qualified
personnel only, as described by the types of product users in the Safety precautions (on
page 40). Do not perform these procedures unless qualified to do so. Failure to recognize and
observe normal safety precautions could result in personal injury or death.
All wiring must be rated for the maximum voltage in the system. For example, if 1000 V is
applied to the front terminals of the instrument, the switching module wiring must be rated
for 1000 V. Failure to recognize and observe normal safety precautions could result in
personal injury or death.
Do not exceed the maximum specifications for the 7706 module. Refer to the specifications
provided in the data sheet. Failure to recognize and observe normal safety precautions could
result in personal injury or death.
The 7706 module provides connections for both hazardous-voltage and low-voltage circuits.
Make sure to install and maintain double insulation between the hazardous-voltage and
low-voltage wiring using supplementary insulation as required. See the "Wire dressing–fully
wired module" figure in this document for more information. Failure to insulate wiring
properly could result in personal injury or death.

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Equipment needed:
▪Flat-blade screwdriver
▪Cable ties
To wire the 7706:
1. Make sure all power is discharged from the 7706 module.
2. Using a screwdriver, turn the access screw to unlock and open the cover.
Figure 2: Screw terminal access
3. Using the flat-blade screwdriver, loosen the terminal screws and install the wires as needed. The channel
designations for the screw terminals are shown in the following figures.

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Figure 3: Channel designations for analog inputs

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Figure 4: 7706 screw terminal output, source, and sense channel designations

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4. Route the wire along the wire path and secure with cable ties as shown in the following figure.
Figure 5: Wire dressing - fully wired module
5. Fill in a copy of the Connection log (on page 22).
6. Attach the screw terminal access cover.
7. Using a screwdriver, press in the access screw and turn to lock the cover.

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7706 simplified schematic
The 7706 has channels that are grouped into two banks of ten channels (twenty channels total). Backplane
isolation is provided for each bank. Each bank also includes separate cold junction reference points. The first
bank contains channels 1 to 10, while the second bank contains channels 11 to 20. Each channel of the
20-channel multiplexer module is wired with separate inputs for HI and LO, providing fully isolated inputs.
Connections to DMM functions are provided through the module backplane connector for the INPUT
connections and SENSE (4-wire resistance) connections.
Channels 21 to 22 (digital output), 23 to 24 (analog output), and 25 (totalizer) are controlled either using the
remote interface or from the front panel. The grounds for these channels are non-isolated. Detailed information
for each channel is provided later in this document.
Channel 26 (2-wire or 4-wire configuration), channel 27 (sense isolation), and channel 28 (input isolation) are
normally automatically configured by the DAQ6510. However, if the module is not to be connected to the
internal DMM, you can control the channels independently. Note that in the schematic, channels 26, 27, and 28
refer to the designations used for control and not actual available channels. For more information, refer to the
instrument reference manual section "Multiple channel operation."
Connect 4-wire sense leads using channels 11 to 20. When the instrument is configured for 4-wire
measurements (including 4-wire resistance, RTD temperature, ratio, and channel average), the channels are
paired as follows:
▪CH1 and CH11
▪CH2 and CH12
▪CH3 and CH13
▪CH4 and CH14
▪CH5 and CH15
▪CH6 and CH16
▪CH7 and CH17
▪CH8 and CH18
▪CH9 and CH19
▪CH10 and CH20
Although the 7706 relays are latching (the 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 reset
command is issued.

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Figure 6: 7706 simplified schematic

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Channel usage
When using remote communications to send commands, be aware of the following channel usage.
Channels
Description
1 to 20
Measurements such as voltage, resistance, temperature, frequency, and period
21 to 22
Eight-bit digital outputs
23 to 24
Sixteen-bit analog outputs (DAC)
25
Totalizer
26
Two-pole or four-pole selection relay; closing channel 26 makes a four-pole measurement
27
Sense terminals to backplane isolation
28
Input terminals to backplane isolation
Installation
Before operating an instrument with a switching module, verify that the switching module is
properly installed and the mounting screws are tightly fastened. If the mounting screws are
not properly connected, an electrical shock hazard may be present.
If you are installing two switching modules, it is easier to install one switching module into slot 2 first, then install
the second switching module into slot 1.
If you have a Keithley Instruments Model 2700, 2701, or 2750 instrument, you can use your existing
switching module in the DAQ6510. Follow the instructions in your original equipment documentation
to remove the module from the instrument, then use the following instructions to install it in the
DAQ6510. You do not need to remove wiring to the module.
For inexperienced users, it is recommended that you do not connect a device under test (DUT) and
external circuitry to the switching module. This allows you to exercise close and open operations
without the dangers associated with live test circuits. You can also set up pseudocards to experiment
with switching. Refer to "Pseudocards" in the Model DAQ6510 Data Acquisition and Multimeter
System Reference Manual for information on setting up pseudocards.
To prevent electric shock that could result in injury or death, never handle a switching
module that has power applied to it. Before installing or removing a switching module, make
sure the DAQ6510 is turned off and disconnected from line power. If the switching module is
connected to a DUT, make sure power is removed from all external circuitry.
If a card slot is unused, you must install slot covers to prevent personal contact with high
voltage circuits. Failure to install slot covers could result in personal exposure to hazardous
voltages, which could cause personal injury or death if contacted.

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Before installing or removing a switching module, make sure the DAQ6510 power is turned
off and disconnected from line power. Failure to comply may result in incorrect operation and
loss of data in the memory.
Required equipment:
▪Medium flat-blade screwdriver
▪Medium Phillips screwdriver
To install a switching module into the DAQ6510:
1. Turn off the DAQ6510.
2. Disconnect the power cord from the power source.
3. Disconnect the power cord and any other cables that are connected to the rear panel.
4. Position the DAQ6510 so you are facing the rear panel.
5. Use the screwdriver to remove the slot cover screws and the cover plate. Retain the plate and screws for
future use.
6. With the top cover of the switching module facing up, slide the switching module into the slot.
7. Press the switching module in firmly to make sure the switching module connector is connected to the
DAQ6510 connector.
8. Use the screwdriver to tighten the two mounting screws to secure the switching module to the mainframe.
Do not overtighten.
9. Reconnect the power cord and any other cables.
Remove a switching module
Before you remove a switching module or begin any testing, make sure that all of the relays are
open. Since some relays may be latched closed, you must open all of the relays before removing the
switching module to make connections. Additionally, if you drop your switching module, it is possible
for some relays to latch closed.
To open all channel relays, go to the CHANNEL swipe screen. Select Open All.
To prevent electric shock that could result in injury or death, never handle a switching
module that has power applied to it. Before installing or removing a switching module, make
sure the DAQ6510 is turned off and disconnected from line power. If the switching module is
connected to a DUT, make sure power is removed from all external circuitry.
If a card slot is unused, you must install slot covers to prevent personal contact with high
voltage circuits. Failure to install slot covers could result in personal exposure to hazardous
voltages, which could cause personal injury or death if contacted.

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Before installing or removing a switching module, make sure the DAQ6510 power is turned
off and disconnected from line power. Failure to comply may result in incorrect operation and
loss of data in the memory.
Required equipment:
▪Medium flat-blade screwdriver
▪Medium Phillips screwdriver
To remove a switching module from the DAQ6510:
1. Turn off the DAQ6510.
2. Disconnect the power cord from the power source.
3. Disconnect the power cord and any other cables that are connected to the rear panel.
4. Position the DAQ6510 so you are facing the rear panel.
5. Use the screwdriver to loosen the mounting screws that secure the switching module to the instrument.
6. Carefully remove the switching module.
7. Install a slot plate or another switching module in the empty slot.
8. Reconnect the power cord and any other cables.
Operation
Before installing or removing a 7706 module, make sure the DAQ6510 power is turned off and
disconnected from line power. Failure to comply may result in incorrect operation and loss of
data in 7706 memory.
This switching module does not support current measurements. If the instrument has the TERMINALS switch
set to REAR and you are working with the slot that contains this switching module, the AC, DC, and digitize
current functions are not available. You can measure current using the front panel or using another slot that
contains a switching module that supports the AC, DC, and digitize current measurements.
If you use remote commands to attempt to measure current when configuring a channel, an error is returned.
Typical connections (channels 1 to 20)
The following examples show typical wiring connections for the following types of measurements:
▪Thermocouple
▪Two-wire resistance and thermistor
▪Four-wire resistance and RTD
▪DC or AC voltage

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Thermocouple connections
Figure 7: Thermocouple connections
Two-wire resistance and thermistor connections
Figure 8: Two-wire resistance and thermistor connections

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Four-wire resistance and RTD connections
Figure 9: Four-wire resistance and RTD connections
DC or AC voltage connections
Figure 10: DC or AC voltage connections

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Digital outputs (channels 21 to 22)
Use the 7706 digital outputs to control items such as indicators, fixtures, switches, solenoids, loads, and relays.
The following figure shows a simplified schematic of the digital output.
Figure 11: Simplified schematic of the digital output
The digital output allows the use of an external power supply up to 42 V.

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Set the digital outputs in 8-bit (byte)
To set the digital output, send the decimal equivalent of the binary pattern.
On each port, bit 7 is the most significant bit (MSB) and bit 0 is the least significant bit (LSB). This makes the
pin 1 screw terminal of each digital port (TE2 and TE1) the LSB, and pin 10 the MSB.
TE2 is channel 21 and TE1 is channel 22. Pins 5 and 6 on each digital port are ground.
To find the decimal equivalent of the binary pattern send the decimal value using the remote interface (as in the
example) or by using the front panel of the DAQ6510.

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Set digital value
You can set a digital value using the front panel or remote commands. The following examples are for a card in
slot 1. If the switching module is in slot 2, replace channel 121 with channel 221.
Using the front panel:
1. Press the HOME key.
2. On the NON-SWITCH swipe screen, select Write.
3. Select channel 121 and select OK.
4. Enter 138 and select OK.
To verify using the front panel:
1. On the NON-SWITCH swipe screen, select Read.
2. Select channel 121 and then select OK. The result displays.
Using SCPI commands:
ROUTe:CHANnel:WRITe 138, (@121)
ROUTe:CHANnel:READ? (@121)
Using TSP commands:
channel.write("121", 138)
print(channel.read("121"))

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Setting the digital outputs in 16-bit (word)
To set the digital outputs in 16-bit, send the decimal equivalent of the binary pattern (similar to 8-bit). The binary
pattern is twice as long as the 8-bit pattern (requiring both digital output ports). Bit 15 is the most significant bit
(MSB) and bit 0 is the least significant bit (LSB). This makes the pin 1 screw terminal of channel 21 (TE2) the
LSB and the pin 10 screw terminal of channel 22 (TE1) the MSB.
To find the decimal equivalent of the binary pattern:
1. Determine the pattern mapped to the screw terminals on the digital output (refer to the example in the
following figure). Setting a bit to a logic 1effectively sets the screw terminal to +5 V, while setting it to a
logic 0sets the screw terminal to 0 V.
2. For each screw terminal (or bit position), multiply the binary value (either a 1 or a 0) by the decimal weight,
as shown in the following figure. The sum of the products is the decimal equivalent value of the binary
pattern. This decimal value can be sent using the remote interface as in the example.

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Set a 16-bit digital value
You can set a 16-bit digital value using the front panel or remote commands. The following examples are for a
card in slot 1. If the switching module is in slot 2, replace channel 121 with channel 221.
Using the front panel:
1. Press the MENU key.
2. Under the Channel column, select Settings.
3. Select channel 121.
4. Select Width and enter 2.
5. Press the HOME key.
6. On the NON-SWITCH swipe screen, select Write.
7. Select channel 121.
8. Enter 49288 and select OK.
9. On the NON-SWITCH swipe screen, select Read.
10. Select channel 121 and select OK. The result displays in hexadecimal.
Using SCPI commands:
ROUTe:WIDTh 2, (@121)
ROUTe:CHANnel:WRITe 49288, (@121)
ROUTe:CHANnel:READ? (@121)
Using TSP commands:
channel.setwidth("121", 2)
channel.write("121", 49288)
print(channel.read("121"))
Figure 12: Typical digital output with external power supply

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Figure 13: Typical digital output with no external power supply
Reactive loads
To prevent damage to the module, do not exceed the maximum signal level specifications of
the module. For reactive loads, be sure to use voltage clamping and current surge limiting.
7706 operation is specified for resistive loads. Reactive loads require voltage clamping for inductive loads and
current surge limiting for capacitive loads to prevent damage to the relays and to external circuitry.

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Analog outputs (channels 23 to 24)
Analog output current limit is 5 mA (maximum).
The 7706 contains two digital to analog converters (DACs). Use these analog outputs for tasks such as
applying a voltage bias to DUTs or analog control. The two analog outputs of the 7706 can provide voltages in
the range of ±12 V. The analog outputs can be set from the front panel or using the remote interface.
The following figure shows a simplified schematic of the analog outputs.
Figure 14: Analog outputs
In the following examples, the 7706 module is in slot 1 of the DAQ6510.
Sample 1: Set analog output 1 (channel 23) to 10.0 V
The following examples are for a card in slot 1. Set channel 23 (analog output 1).
Using the front panel:
1. Press the HOME key.
2. On the NON-SWITCH swipe screen, select Write.
3. Select channel 123.
4. Enter 10 and select OK.
Using SCPI commands:
ROUTe:CHANnel:WRITe 10.0, (@123)
Using TSP commands:
channel.write("123", 10.0)
Refer to “Front panel operation” in the Model DAQ6510 Reference Manual for more information on
menus and key locations. Voltage may be set in 1 mV steps (values are rounded to the nearest
millivolt).