Increase Precision on Analog Input DAQ Device

Updated Dec 31, 2022

Environment

Hardware

  • Multifunction I/O Device
  • C Series Multifunction I/O Module

Software

  • Measurement & Automation Explorer (MAX)
  • LabVIEW

Driver

  • NI-DAQmx

When taking an analog input measurement it is important to set the appropriate range to get the best precision. Many NI devices have different input ranges that can be modified while others do not.

  1. Check the datasheet to see what is listed under Input Range to determine if your device supports modifying the voltage range. It is possible to change the analog input range on most NI devices but some, like the USB-6009,  can only change the range using a differential task. Below is the relevant section of the USB-6009 datasheet:
 
  1. Thus, setting the voltage range to -2.5 V to +2.5 V, the full 14-bit-precision will be applied to a smaller range, increasing precision.
    1. This can be done in NI MAX or using the DAQ Assistant by changing the Signal Input Range as shown below:
 
  1. In LabVIEW, wiring in new values to the Minimum Value and Maximum Value input terminals of the DAQmx Create Channel VI will accomplish the same.
DAQmx_Create_Channel.png

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