Error -201493 Performing a Shunt Calibration

Updated Sep 5, 2018

Reported In

Hardware

  • NI-9218
  • NI-9237
  • NI-9235
  • NI-9236

Driver

  • NI-DAQmx

Issue Details

I am trying to perform a shunt calibration of my bridge based sensor using the DAQmx Perform Shunt Calibration.vi, but I am getting the following error:

Error -201493 occurred at an unidentified location

Possible reason(s):

Shunt calibration failed. The calculated gain adjust is out of range. Ensure that the shunt calibration terminals are connected properly and that the shunt resistance and shunt element location settings match how the hardware is wired.

Solution

There are several reasons for this error to appear:

Loose or Incorrect Connections
Ensure your bridge sensor has all the required connections as shown in your module's documentation, or in Connecting Strain Gages and Shunt Resistors to the NI-9237, and that they are firmly connected.

Shunt Element Location
The shunt element location is not arbitrary. The number of the resistor depends on its position in the bridge as shwn in the DAQmx Perform Shunt Calibration.vi help. Entering the wrong resistor value to the DAQmx Perform Shunt Calibration.vi will cause the error.

Incorrect Shunt Resistance
Using a wrong shunt resistance value on the DAQmx Perform Shunt Calibration.vi can cause the error because the measured value will likely fall out of the expected range.

Using an External Shunt Resistor
Not all device support the use of the DAQmx Perform Shunt Calibration.vi with external shunt resistors. For example, C Series modules can only use the VI with their built-in shunt resistor. If an external resistor is used with a device that does not support it, the actual shunt resistance value will be a combination of the built-in and external resistors, leading to an incorrect calibration.

Using a Simulated Device
NI-DAQmx simulated devices don't support some features, shunt calibration included. Enabling the shunt calibration on a simulated device will always return the error.

Additional Information

If you want to shunt calibration using an external resistor on a module that does not support this through the DAQmx Perform Shunt Calibration.vi, you will need to perform the calibration manually following the next steps:
 
  1. Calculate the ideal output of the bridge with the external shunt resistor in place.
  2. Take measurements with the external resistor in place. Averaging a large number of samples will lead to a more accurate calibration.
  3. Find the ratio of 1. and 2.
  4. Stop the task and write the result of 3. to the Gain Adjustment Property using an NI-DAQmx Channel Property Node.
  5. Remove the external shunt resistor and start the task again.

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