Model 2790 SourceMeter
®
Switch System User’s Manual 3-3
Card configuration
Unlike the 7751, 7752, and 7753 modules, the 7702 module supports system channel
operation. That is, when an input channel is closed, other channels on the module automat-
ically close to connect the input to the backplane (DMM) of the Model 2790.
Figure 3-1 is a simplified schematic diagram of the Model 7702 module. As shown, the
Model 7702 has channels that are grouped into two banks of twenty channels (forty chan-
nels total). Backplane isolation is provided for each bank. The first bank contains channels
1 through 20 while the second bank contains channels 21 through 40. Each channel of the
40-channel multiplexer card is wired with separate inputs for HI/LO providing fully iso-
lated inputs. The Model 7702 also provides two channels of current input, Channels 41
and 42.
Although the Model 7702 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.
For a 4-wire function or operation (Ω4, RTD TEMP, Ratio, or Channel Average), the chan-
nels are paired as follows:
• CH1 and CH21 • CH6 and CH26 • CH11 and CH31 • CH16 and CH36
• CH2 and CH22 • CH7 and CH27 • CH12 and CH32 • CH17 and CH37
• CH3 and CH23 • CH8 and CH28 • CH13 and CH33 • CH18 and CH38
• CH4 and CH24 • CH9 and CH29 • CH14 and CH34 • CH19 and CH39
• CH5 and CH25 • CH10 and CH30 • CH15 and CH35 • CH20 and CH40
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