VXI VT1422A, User Manual

Page: 37 / 529

Field Wiring 37 Chapter 2
Sense SCPs and
Output SCPs
Some SCPs provide input signal conditioning (sense SCPs such as filters
and amplifiers) while others provide stimulus to the measurement circuit
(output SCPs such as current sources and strain bridge completion).
In general, channels at output SCP positions are not used for external signal
sensing but are paired with channels of a sense SCP. Two points to remember
about mixing output and sense SCPs:
1. Paired SCPs (an output and a sense SCP) may reside in separate
VT1422As. SCP outputs are adjusted by *CAL? to be within a
specific limit. The Engineering Unit (EU) conversion used for a sense
channel will assume the calibrated value for the output channel.
2. Output SCPs, while providing stimulus to the measurement circuit,
reduce the number of external sense channels available to the VT1422A.
Figure 2-2 illustrates an example of "pairing" output SCP channels with sense
SCP channels (in this example, four-wire resistance measurements).
Note
Each channel line
represents both a
Hi and Lo input
SCP
3
(sense)
SCP
4
(output)
Input Mult
iplexer
Ch 24
Ch 31
Ch 32
Ch 39
Terminal Module
sense Hi
sense Lo
outpu
t Hi
output Lo
Figure 2-2. Pairing Output and Sense SCP Channels