Chapter 2
Configuration and Installation
2-24
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the excitation channels, and one pair of screw terminals connects to the
chassis ground.
The following cautions contain important safety information concerning
hazardous voltages and terminal blocks.
Caution
When using the terminal block with high common-mode voltages, you must
insulate your signal wires appropriately. National Instruments is
not
liable for any damages
or injuries resulting from inadequate signal wire insulation.
Caution
If high voltages (
≥
42 V
rms
) are present, you must connect the safety earth ground
to the strain-relief tab. This complies with UL 1244 and protects against electric shock
when the terminal block is
not
connected to the chassis. To connect the safety earth ground
to the strain-relief tab, run an earth ground wire in the cable from the signal source to the
terminal block. National Instruments is
not
liable for any damages or injuries resulting
from inadequate safety earth ground connections.
SCXI-1320 and SCXI-1328 Terminal Blocks
When connecting your signals to the SCXI-1320 terminal block for use
with the SCXI-1121, follow the labeling on the SCXI-1320 indicated under
the module type column for the SCXI-1121 as indicated in Figure 2-11.
When connecting your signals to the SCXI-1328 high-accuracy isothermal
terminal block for use with the SCXI-1121, follow the labeling on the
SCXI-1328 indicated along the module type row for the SCXI-1121 as
indicated in Figure 2-12.
SCXI-1321 Offset-Null and Shunt-Calibration Terminal Block
The SCXI-1321 terminal block operates only with Revision C and later
SCXI-1121 modules.
In addition to the 18 screw terminals, the SCXI-1321 has circuitry for
offset-null adjust of Wheatstone bridges as well as a shunt resistor for
strain-gauge shunt calibration. This terminal block works especially well
with bridge-type transducers such as strain gauges. The SCXI-1321 can
also easily accommodate thermocouples, RTDs, thermistors, millivolt
sources, volt sources, and current-loop receivers.