Measure the Dynamic Range of My Data Acquisition Device with National Instruments Software

Updated Jul 23, 2019

Reported In

Software

  • LabVIEW Full
  • LabVIEW NXG
  • DAQExpress

Issue Details

How do I measure the dynamic range of My Data Acquisition Device in LabVIEW, LabVIEW NXG or DAQExpress?

Solution

The dynamic range of a DAQ device is the ratio of the highest signal level to the smallest signal level a circuit can measure (usually equal to the noise floor), normally expressed in dB.

One approximation of the Dynamic Range is the dB equivalent of Idle Channel Noise which you can find using the following method:
  1. ​Terminate an input channel.
  2. Calculate the offset and subtract it from the original signal.
  3. Convert the remaining signal to Vrms (Idle Channel Noise).
  4. Convert input range to Vrms (Full Scale Amplitude of AI Channel).
  5. Divide the two values and convert to dB.

Below is a LabVIEW code snippet showing how to perform the calculation using the Mean VI , RMS VI and Logarithm Base 10 Function.
 

Likewise, in LabVIEW NXG and DAQExpress, you can use the Statistics, Amplitude Measurements (in AC DC and RMS mode) and Logarithm Base 10 nodes to perform the calculation.

Additional Information

The industry standard (and SVMS Dynamic Range SubVI) technically requires a high quality -60dB input tone instead of a terminated input channel.  For most NI devices you get the same number using either method.

The same method should be valid in different Application Development Environments (ADE). Refer to your ADE documentation to locate functions or methods equivalent to those used in the shown LabVIEW snippet.

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