NI-9203 Generates Internal Noise When Acquiring Data

Updated Sep 18, 2018

Reported In

Hardware

  • NI-9203

Software

  • LabVIEW 2015 Full
  • LabVIEW

Issue Details

I have a noisy measurements of the current 4-20mA of NI-9203 using a cDAQ.
The noise frequency seems to be exactly equal to the specified sampling rate of the data by MAX or LabVIEW.
It seems that noise is generated internally by the NI-9203.
 

Solution

Verify the noise by doing a zero-signal test and running following VI. This test should be done with zero-signal. Please wire the analog input that you will be measuring on to the ground of the card in order to only read internal noise.





 

Additional Information

For calculating the theoretical noise in nA:
  1. Find the theoretical standard deviation for 9203 in its datasheet.
  2. Input noise is: 1 LSBrms RMS and 7 LSB for Peak-to-Peak (meaning any two points should be within 7 LSB's and on average the noise is within 1 LSBrms).
  3. To calculate noise (with a 99% confidence level i.e. 3 sigma) we use the formula: Noise = ((2*Range)/(2^Bit))*LSBrms*3.
Ex: The theoretical noise of the NI-9203 in bipolar mode will be around 2000 nA. 

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