Filtering - Phase Angles & Time Delays

Tech Note

This newsletter, with the link below to App Note AN113 "Filtering -Phase Angles & Time Delays" can be considered as Part 2 to App Note AN112 "Filtering in Signal Conditioning Modules". This one provides design considerations relative to phase angles and time delays.

At first thought, the need to pass information of interest on to a data acquisition system and to block unwanted signals may appear to be solved by a simple low-pass, band-pass, or high-pass filter. This second application note explores in some detail the significance of phase shift and time delay that are unavoidable in the design of these different types of filters. A better understanding of these characteristics may help you on your next data-acquisition project!

Industrial signal conditioning modules (SCMs) require internal multiple-pole low-pass filtering that has:

  1. specified 3dB frequency (i.e. cutoff, corner, knee frequency)
  2. steep attenuation well above the 3dB frequency (20dB per pole per frequency decade)
  3. flat response with minimum ringing or ripples within the pass-band
  4. anti-aliasing function on the field side prior to amplification

Dataforth design engineers use rigorous design tools to provide all of these multi-pole SCM filter characteristics.

Download App Note AN113 and explore the many details of filter design.

This application note also has an interactive Excel spreadsheet which you can use to enter your own parameters and see how phase shift and time delays are affected in a 2-pole filter design.

Remember, our Application Engineers can assist you with signal conditioner selection over the phone or via fax and email. Call us at our manufacturing facility in Tucson at 520-741-1404 (fax 520-741-0762) or Email us at

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