Chapter 4 Connecting and Using Accessories and Transducers
Getting Started with SCXI 4-28 www.ni.com
Note
Always connect the current excitation terminals outside the sense terminals as
showninbothFigures4-14and4-15.
Each approach has its advantages and disadvantages, as listed in Table 4-6.
Analog Output Channel Signal Connections on the SCXI-1124
You can connect each SCXI-1124 output channel independently for
voltage output or current output. Each channel is referenced to its own
isolated ground. Each isolated ground can have up to 250 V
rms
of CMV
between itself and any other channel ground or chassis ground. The
following illustrations show how to make different types of signal
connections. The dots in the figures indicate where you connect wires tothe
SCXI-1325 terminal block. For information on how to connect the wires to
your terminal block, consult the SCXI-1325 High-Voltage Terminal Block
Installation Guide.
Table 4-6. Pros and Cons of Two-Wire and Four-Wire Connections with Current-Excited Transducers
Type Pros Cons
Series connection with
two-wire scanning
16 transducers per module
All transducers are continuously excited
Limitedto5kΩ total
resistance
Two-wire connections are easier to
connect because of fewer wires
No isolation between
channels
Independent connection
with four-wire scanning
5kΩ per channel
250V
rms
common-mode voltage(CMV)
isolation between transducers
Eight transducers maximum
per module
More connections
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