Keithley 2700, User Manual, Page: 63 / 500

2-8 Close/Open Switching Module Channels Model 2700 Multimeter/Switch System User’s Manual
4-wire functions (paired channels)
A 4-wire function, such as
Ω
4, 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 shows an example of system channel connections for a 4-wire function.
Assume a Model 7700 switching module is installed in slot 1 of the mainframe, and a
4-wire function, such as
Ω
4, is selected. When channel 101 is closed using the system
channel 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
Figure 2-2 that the Channel 23 relay closes to isolate channel 1
from channel 11.
The complete simplified schematic of Model 7700 is provided in Figure 2-12 .
Figure 2-2
4-wire system channel connections to Model 2700 DMM
DMM Model 7700 Switching Module
Model 2700
Slot 1
Close channel 101
System channel operation:
(closed position
shown
)
Channel 1
Relay
HI
LO
HI
LO
Input
Channel 25
Backplane
Isolation
Relay
Channel 1
Channel 11
Relay
HI
LO
HI
LO
Sense
Channel 24
Backplane
Isolation
Relay
Channel 11
Channel
23
2-Pole/4-Pole
Relay