4-Wire Functions (Paired Channels) - Keithley SourceMeter 2790 Reference Manual

2-8
Figure 2-1
7702 2-wire system channel connections to Model 2790 DMM

4-wire functions (paired channels)

A 4-wire function, such as Ω4, requires that another measurement channel be paired to the
system channel. For example, if the switching module has 40 measurement channels,
channels 1 through 20 can be used as the system channel, while channels 21 through 40
are used as the paired channel. For a switching module that has 40 measurement channels,
channel 1 is paired to channel 21, channel 2 is paired to channel 22, channel 3 is paired to
channel 23, and so on.
Figure 2-2
Assume a Model 7702 switching module is installed in slot 2 of the mainframe and a
4-wire function, such as Ω4, is selected. When channel 201 is closed using the system
channel close keys, the Channel 1 relay and the input backplane isolation relay
(Channel 45) closes to connect the channel to DMM Input. Also, the Channel 21 relay and
the sense backplane isolation relay (Channel 44) close to connect the paired channel to
DMM Sense. Also note in
from channel 21.
The complete simplified schematic of Model 7702 is provided in
Model 7702 Switching Module
Channel 1
HI
Channel 1
LO
System channel operation:
Close channel 201
shows an example of system channel connections for a 4-wire function.
Figure 2-2
Model 2790 SourceMeter
Model 2790
Channel 45
Relay
Backplane
Isolation
Relay
that the Channel 43 relay closes to isolate channel 1
®
Switch System Reference Manual
Slot 2
DMM
HI
Input
LO
Figure 2-13.