Bridge Measurements Railing Out Quickly

Updated May 16, 2018

Reported In

Hardware

  • NI-9237
  • NI-9219

Issue Details

I'm using an NI-9237 to take full-bridge measurements from a device. When my sensor increases its output, it appears to work properly, but the voltage caps out around 25 mV and won't increase any further, even if I add a custom scale or change the excitation voltage. Why does this happen, and can I push past this limit?

Solution

By default, bridge setups will return a ratiometric measurement. This means that the mV measurement is automatically divided by the excitation voltage, and the resultant is conveyed in mV/V. If you are using a 9237, the highest value the device can handle is 25 mV/V.

If this specification prevents you from realizing the full range of your device, you have a few options:
  1. Change to a different module with a higher mV/V rating for full bridge measurements, such as the 9219.
  2. Buy a different sensor with a lower sensitivity. The higher the sensitivity, the more voltage change there is when more pressure or force is applied.
  3. Include external circuitry to reduce the mV input from the sensor. This may require the use of a buffer and a voltage divider.

WAS THIS ARTICLE HELPFUL?

Not Helpful