4-Wire Functions (Paired Channels) - Keithley 2700 User Manual

2-8 Close/Open Switching Module Channels

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 20 measurement channels,
channels 1 through 10 can be used as the system channel, while channels 11 through 20
are used as the paired channel. For a switching module that has 20 measurement channels,
channel 1 is paired to channel 11, channel 2 is paired to channel 12, channel 3 is paired to
channel 13, and so on.
Figure 2-2
Assume a Model 7700 switching module is installed in slot 1 of the mainframe, and a 4-
wire function, such as Ω4, is selected. When channel 101 is closed using the system chan-
nel close keys, the Channel 1 relay and the input backplane isolation relay (Channel 25)
closes to connect the channel to DMM Input. Also, the Channel 11 relay and the sense
backplane isolation relay (Channel 24) close to connect the paired channel to DMM
Sense. Also note in
channel 11.
The complete simplified schematic of Model 7700 is provided in
Figure 2-2
4-wire system channel connections to Model 2700 DMM
System channel operation:
Close channel 101
shows an example of system channel connections for a 4-wire function.
Figure 2-2
Model 7700 Switching Module
Channel 1
HI
Channel 1
LO
(closed position
Channel 11
HI
Channel 11
LO
Model 2700 Multimeter/Switch System User's Manual
that the Channel 23 relay closes to isolate channel 1 from
Model 2700
Relay Channel 25
Backplane
Channel
23
2-Pole/4-Pole
shown
)
Relay Channel 24
Backplane
Figure 2-12.
Slot 1
DMM
HI
Input
LO
Isolation
Relay
Relay
HI
Sense
LO
Isolation
Relay