Enable Programmable Filter on National Instruments DAQ Card

Updated Aug 29, 2019

Reported In

Hardware

  • PXI Analog Input Module
  • PXI Multifunction I/O Module

Software

  • LabVIEW

Driver

  • Measurement & Automation Explorer (MAX)

Issue Details

I want to utilize the filter on NI DAQ card. I have noise in my environment that's coming through to my signal and saw that my card has filtering capabilities. What is the cutoff frequency of this filter? How do I enable the lowpass filter on my National Instruments data acquisition card?  

Solution

The cutoff frequency of your card can be found in the device's user manual. The devices user manual can be found by searching for the device on the Product Manual search page. Once you open the user manual, locate the Analog Input Filter section in the document. This section will provide the specific cutoff frequency for your card.

You can enable the filter in both NI Measurement & Automation Explorer and in LabVIEW:

  • In NI-Measurement & Automation Explorer, you can enable the filter by creating an Analog Input task for your DAQ device. Once you have created the Analog Input Task, select the Device tab listed under Voltage Input Setup. In this tab, you should be able to select the Lowpass Filter Cutoff Frequency that is offered by your device in order to enable the filter. Note: You can use the DAQ Assistant to use this task in LabVIEW.
  • In LabVIEW, you can enable the filter with a setting found in the DAQmx Channel Property Node in LabVIEW, located in the DAQmx Pallet. Navigate into the property tree to: Analog Input » General Properties » Filter » Analog Filter » Lowpass » Enable. 

Note: In LabVIEW, you can find the default value of this property by following the steps below.

  1. Right click on the property node and select Change All To Write. This will output whatever value is currently held by that property, which will be the default if nothing has been written to it yet.
  2. Duplicate the property node by holding CTRL and dragging your previous property node. 
  3. Create an Indicator on the output to be able to display that value on your front panel. Below is an example image of the outcome.
 

Additional Information

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. For cards that do not have this filter, consider National Instruments DSA (Dynamic Signal Acquisition) Boards.

Analog triggers for M Series boards specifically 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.

WAS THIS ARTICLE HELPFUL?

Not Helpful