Worldwide Technical Support - National Instruments SCXI Series Quick Start Manual

• Verify correct placement and configuration of the modules. If you did not auto-detect
modules, modules installed in the chassis may not be configured in software. Alternately,
modules configured in software might not match the ones installed in the chassis.
All my channels float to a positive rail when I try to take a measurement. How do I correct
the problem?
Make sure that the signal reference settings for the DAQ device match the SCXI module. For
example, if the device is configured for NRSE, make sure that the cabled SCXI module shares
the same configuration. Matching configurations can require a change to the jumper setting of
the module.
I am using one of the following modules—SCXI-1100, SCXI-1102/B/C, SCXI-1112, or
SCXI-1125—with one of the following terminal blocks—SCXI-1300, SCXI-1303, or
SCXI-1328—to measure temperature with a thermocouple. How do I stop the
thermocouple reading from fluctuating?
Average the temperature readings to minimize fluctuations. Also, ensure proper field wiring
techniques. Most thermocouples are floating signal sources with low common-mode voltage;
they require a path for bias currents from the SCXI module amplifier to ground. Make sure that
you have grounded the negative lead of each floating thermocouple through a resistor. Refer to
the terminal block documentation for impedance values. For grounded thermocouples, ensure
that there is not a high common-mode voltage present on the thermocouple ground reference.

Worldwide Technical Support

For additional support, refer to
information for signal conditioning products, refer to the Technical Support Information
document packaged with your device.
National Instruments corporate headquarters is located at 11500 North Mopac Expressway,
Austin, Texas, 78759-3504. National Instruments also has offices located around the world to
help address your support needs.
SCXI Quick Start Guide
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