Why Do I Get Error -201398 When Trying to Calibrate My Strain Gage Module?

Updated Feb 14, 2018

Reported In

Hardware

  • C Series Strain/Bridge Input Device

Issue Details

I'm trying to take readings from a strain gage with my quarter-bridge strain gage module, but it won't calibrate. It gives an error of over 1000% and says error -201398 has occurred at strain gage calibration. (Requested value is not supported for this property). 

Why is this happening?

Solution

This could be caused by the lead wire resistance. Quarter-bridge measurements are inherently sensitive to accuracy degradation due to the lead resistance of wiring from the sensor to the measurement device. The maximum usable lead wire resistance can vary, with a 120 ohm NI-9235 it's around 18 ohms but may vary between devices and resistances.
 

Additional Information

There are a number of things that can affect the lead wire resistance. The material, length and cross sectional area of the wire will have an effect on its resistance. If a strain gage has suddenly started giving this error the lead wire resistance might have changed due to the temperature changing or the wire becoming more taught.

If a large lead wire resistance is expected then a half-bridge or full-bridge completion module might be preferable.  

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