Error -200380 When Calibrating SCXI-1520 Using NI-DAQmx

Updated Nov 12, 2018

Reported In

Hardware

  • SCXI-1520
  • SCXI-1314

Software

  • SignalExpress

Driver

  • NI-DAQmx

Issue Details

I am using an SCXI-1520 module with an SCXI-1314 terminal block and I want to perform shunt calibration to offset nulling using the DAQ Assistant in NI-DAQmx. Assuming my configuration settings are correct for my strain gauge, when I click the Calibrate button on the Device page in the DAQ Assistant, I receive the following message:
Error -200380: Strain gauge calibration procedure has failed. Ensure that the strain gauges are connected to all the specified strain channels, the strain gauge connections are appropriate for their bridge type configurations, the shunt resistor location is specified correctly, and that your hardware jumpers (if any) are set up correctly.
How can I resolve this error and correctly calibrate my SCXI-1520?

Solution


The first step in diagnosing this problem is to double-check that all your device settings are correct. This includes selecting the correct shunt resistor location and resistor value. NI-DAQmx reads the bridge completion method you selected in Measurement & Automation Explorer and filters the shunt resistor locations so you can only select the possible shunt resistor locations that conform to the selected bridge completion method. If the wrong bridge completion method was selected, the selected shunt resistor location may be incorrect. However, if all your settings are correct, the problem could be in the precision of the bridge completion resistor.
For proper operation and calibration, you need a bridge completion resistor that precisely matches your nominal gauge resistance. Chapter 1 of the SCXI-1520 User Manual (linked below) explains that the SCXI-1520 has a limitation on the voltage range that it can null. For example, if you select the quarter-bridge II completion method and do not match your nominal gauge resistance with the quarter-bridge completion resistor value, you cause an offset voltage. By default, the SCXI-1314 terminal block has a 350 ohm socketed quarter-bridge completion resistor. If the gauge resistance of your strain gauge is not 350 ohms, you must replace the QTR resistor with a precision 120 ohm resistor in order to not exceed the maximum nulling capability of the SCXI-1520 module. The location of these quarter-bridge completion resistors can be seen in Figure 1 below.



Figure 1. Quarter Bridge Completion Resistor Location Schematic

These small black resistors can easily be removed and reinserted using a set of tweezers as they are press fit instead of soldered into place. 
The precision of the bridge completion resistor(s) is a very important consideration because the actual resistance of non-precision resistors can vary by up to 10 percent of their overall rating. This variance can be too far out of range for the SCXI-1520 to completely null the offset. Always use precision resistors for the bridge completion resistors on the SCXI-1314.


 

Additional Information


Additional strain gauge calibration troubleshooting information is located in the Troubleshooting Your Strain Gauge Calibration section of the DAQ Assistant Help found in Measurement & Automation Explorer (Help » Help Topics » DAQ Assistant).

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