Bad Readings or Noise Measuring Load Cell or Force Sensor

Issue Details

Solution

• Use a LabVIEW shipping example (Bridge-Continuous Input) or Test Panels in NI MAX to verify that the raw values coming into your software are correct.
  • If test panels still show the incorrect values, test the measurement from the sensor output with an oscilloscope or DMM to verify the sensor is outputting the expected data.
• Ensure the channel is appropriately connected. Refer to Connecting Strain Gauges and Shunt Resistors to the NI-9237 or to your module documentation for additional information.
• 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.
• If the sensor and module are located in an area with a noisy environment, test the measurement in a different location to check if noise in the environment is causing the problem.

• 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.
  • When configuring the sensor in the NI-DAQmx Task, make sure you enter the correct sensor specifications (for example, the bridge resistance). Entering wrong values can lead to incorrectly scaled data.
• 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.