Bad Readings Measuring Load Cell With NI-9237

Updated Jan 11, 2019

Reported In

Hardware

  • NI-9237

Software

  • SignalExpress
  • LabVIEW

Issue Details

I have a load cell connected to my NI-9237 in either half or full bridge configuration, and am seeing strange readings in my software. What could be causing this?

Solution

  • Use a LabVIEW shipping example or Test Panels in NI MAX to verify that the raw values coming into your software are correct. 
  • Move your sensor to another channel in the module to verify the channel is working properly 
  • Move the module to a different slot in the chassis to verify your chassis is working properly
  • With the 9237 it is important to make sure you are frequently calibrating the device in NI MAX
    • If you are seeing a constant offset, this step will help to adjust the readings

It is important with Force (bridge) tasks to ensure your NI-DAQmx task has been configured correctly to ensure proper readings:
  • Please follow the Configuring a Load Cell in MAX with the NI 9237 tutorial to ensure every aspect of the task has been configured correctly.
  • If you are seeing erratic or noisy measurements in a test panel in NI MAX, you may want to refer to our article on Incorrect Test Panel Readings on the NI 9237
  • If you using an external power supply on NI 9237, ensure you have the Remote sensing inputs (RS+ and RS-) connected to the load cell to compensate any power supply instability or noise and/or any gain error caused by long cables. Even if your sensor does not have the Remote sensing wires, connect the NI 9237 Remote sensing inputs to its excitation ports (RS+ connected to Ex+ and RS- connected to EX-). In that case, the compensation will be just for power supply instability or noise.
  • Finally, refer to our Field Wiring and Noise Considerations for Analog Signals white paper for general best practices on improving analog input readings with NI hardware. 

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