Using the Programmable Filter on M Series Boards

Updated May 3, 2018

Reported In

Hardware

  • PXI-6289
  • PCI-6281
  • PXI-6281
  • PCI-6280
  • PXI-6280
  • PCI-6284
  • PXI-6284

Driver

  • NI-DAQmx

Issue Details

I want to utilize the filter on my M Series board. I have noise in my environment that's coming through to my signal and saw that my M Series board (628x) has filtering capabilities. What is the cutoff frequency of this filter, and how do I use it?

Solution

All high resolution M-Series cards are equipped with a low pass filter that can be programmatically enabled or disabled. When the filter is on, the filter cutoff frequency (-3 dB attenuation point) is 40 kHz (known as the "Small Signal Bandwidth"). When not enabled, the full bandwidth for an analog input signal is 750 kHz.
  1. Create a DAQmx Channel Property Node.
  2. Set the property to Analog Input » General Properties » Filter » Analog Lowpass » Enable
  3. Set Enable to True. See the following screenshot of the property node: 
 

Additional Information

For more information on this filter and the Small Signal Bandwidth, please see the M Series User Manual

Anti Aliasing

Anti-Aliasing filters are often needed for communicating with sensors that experience high frequency noise and in applications where frequencies above the Nyquist frequency are not of interest. The 628x series does not have an anti-aliasing filter. For this filter, consider National Instruments DSA (Dynamic Signal Acquisition) Boards.

Analog Triggering

Analog triggers for M Series boards can be put through one of the analog input channels on the board, or the APFI analog input trigger line. With the filter off, the analog trigger bandwidth is 700 kHz if the signal is wired through an analog input channel. If put through the APFI line, the analog trigger bandwidth is 5 MHz whether the filter is on or off.

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