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Model 7702 Multiplexer Module Instructions for use with DAQ6510
Schematic diagram
The simplified schematic diagram of the 7702 is shown in the following figure.
Channels 1 to 40 are used for all measurements except current. Channels 41 and 42 are used for current only.
There are two backplane relays (channels 44 and 45) to connect the input channels to the backplane of the
instrument. With a 2-wire function (except current) selected, channel 45 closes. With a 4-wire function selected,
channels 44 and 45 close.
There is a 2-pole/4-pole relay (channel 43) between channels 1 to 20 and channels 21 to 40. When a 2-wire
function (such as DC voltage) is selected, channel 43 opens (2-pole position) to allow any of the 40 channels
to be connected to the input backplane.
When a 4-wire function is selected, channel 43 closes (4-pole position) to isolate channels 1 to 20 from
channels 21 to 40. When one of the channels 1 to 20 is closed, its paired channel (21 to 40) also closes to
connect the sense channel to the sense backplane.
For the two current channels (41 and 42), signal HI and LO are routed directly to the backplane when the
channel is closed. The relays on the current channels are break-before-make.
The Input and Sense terminals are connected to the inputs of channels 45 and 44 (isolation relays).
The Amps terminals are connected directly to the DMM.
Channels 43, 44, and 45 in this schematic refer to designations used for control and not actual
available channels. For more information, refer to the applicable instrument reference manual.
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077144400 / April 2018
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