Getting Noisy Measurements With PCIe-6363 Board When Powering Sensor With +5 V of the Board

Updated Aug 21, 2020

Reported In

Hardware

  • PCIe-6363

Driver

  • NI-DAQmx

Issue Details

I am trying to measure the output signal of my microphone using the AI of the PCIe-6363. My microphone requires an excitation DC voltage between 2.4 and 5.5 V, so for this purpose, I am using the +5 V output of the board. However, I am getting some noisy measurements as shown below:

 How can I fix this?
 

Solution

This behavior is expected when your sensor requires a precise excitation voltage source to be low noise and you use the + 5 V output of your PCIe-6363 for this purpose.  The output of the user +5 V line on the 6363 (and many X Series cards) are not well conditioned, and the power supply that supplies power to that user +5 V line has sawtooth noise on it's output. Depending on the loading of the +5 V line the frequency and amplitude of that noise may change (larger loads, smaller amplitude, faster frequency noise).

But if you are looking for a precision 5 V line, an option on the X Series line is to use one of the AO channels to provide a continuous 5 V DC signal. The accuracy of that output will be specified in the specification sheet. Otherwise, you can use another external DC power supply.