Model 7700 Multiplexer Module Instructions for use with 2750
4 077182400 July 2023
Channels 1 through 20 are used for all measurements except current. Channels 21 and 22 are used for
current only.
There are two backplane relays (channels 24 and 25) that connect the input channels to the backplane of the
instrument. With a 2-wire function (except current) selected, channel 25 closes. With a 4-wire function selected,
both channels 24 and 25 close.
There is a 2-pole/4-pole relay (channel 23) between channels 1 to 10 and channels 11 to 20. When a 2-wire
function (such as DCV) is selected, channel 23 opens (2-pole position) to allow any of the 20 channels to be
connected to the input backplane.
When a 4-wire function is selected, channel 23 closes (4-pole position) to isolate channels 1 through 10 from
channels 11 through 20. When one of channels 1 to 10 is closed, its paired channel (11 through 20) also closes to
connect the sense channel to the sense backplane.
For the two current channels (21 and 22), signal HI and LO are routed directly to the backplane when the channel
is closed.
The Input and Sense screw terminals are connected to the inputs of channels 24 and 25 (backplane isolation
relays). The AMPS screw terminal is connected directly to the instrument.
Channels 23, 24, and 25 in this schematic refer to designations used for control and not actual
available channels. For more information, refer to the instrument reference manual. Also, AMPS and
LO can be connected to another instrument, but you cannot control them through the front panel or by
using remote communications.
If channels 1 through 20 are not connected to the internal DMM, channels 24 and 25 can be controlled
independently using multiple channel operation. Refer to the Model 2750 Multimeter/Switch System User's
Manual, part number 2750-900-01, for more information on multiple channel operation.
Connections
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
13). 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.
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