B-2 Model 7700 Connection Guide Model 2750 Multimeter/Switch System User’s Manual
Card configuration — schematic
Figure B-1 shows a simplified schematic diagram of the Model 7700 module. As shown,
the Model 7700 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 through 10
while the second bank contains channels 11 through 20. Each channel of the 20-channel
multiplexer card is wired with separate inputs for HI/LO providing fully isolated inputs.
The Model 7700 also provides two channels of current input, Channels 21 and 22.
Although the Model 7700 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.
Connections to DMM functions for system channel operation are provided through the
card backplane connector.
• Current provided through two protected channels (Channels 21 and 22).
• INPUT connections.
•SENSE (Ω4-wire) connections.
AMP and LO common connections to the DMM are also provided.
Channel 23 (2W/4W Configuration), Channel 24 (Sense Isolation), and Channel 25 (Input
Isolation) are normally automatically configured by the 2750 for system channel opera-
tion. However, by using multiple channel operation (refer to Section 2), channels can be
individually controlled.
NOTE Connect 4-wire sense leads using channels 11–20.
To disconnect channels 11–20 from channels 1–10, send:
ROUT:MULT:CLOS (@123) (note opposite logic)
When automatically configured for 4-wire measurements (including 4-wire Ω, RTD tem-
perature, ratio, and channel average) the channels are paired as follows:
• CH1 and CH11 • CH6 and CH16
• CH2 and CH12 • CH7 and CH17
• CH3 and CH13 • CH8 and CH18
• CH4 and CH14 • CH9 and CH19
• CH5 and CH15 • CH10 and CH20
2750-900-01.book Page 2 Wednesday, August 3, 2011 7:56 AM
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