Low pass filter

Discussion in 'General Electronics Chat' started by Ritha, Jul 16, 2013.

  1. Ritha

    Thread Starter New Member

    Jul 16, 2013
    I am supposed to remove the noise present in a pressure transducer.
    I connected the transducer to an oscilloscope and noticed some spikes in the waveform.

    Though I couldn't identify the exact amount of noise, I could find out some disturbance in the signal.

    I need help regarding this. I am supposed to use a low pass filter (in software). But I do not have any idea of what should be the order of it. Which type of filter (Butterworth, Chebyshev, etc.,) should be used.

    This extends to writing the code in C and matlab too.
  2. Wendy


    Mar 24, 2008
    The Completed Projects Forum is for Completed Projects only. It is meant to allow members to show plans for projects they built so other members can duplicate them if desired. New threads are also automatically moderated per Moderator review for this reason. Your thread does not belong in this forum, and was moved here.
  3. crutschow


    Mar 14, 2008
    The order of the filter required depends upon the frequency and amplitude of the noise versus the frequency and amplitude of the signal. You need to tell us both.

    Software filters can't remove noise above 1/2 the sample frequency of the A/D converter so you likely will need to add a simple RC low-pass filter in front of the A/D input.
  4. Papabravo


    Feb 24, 2006
  5. Hagen

    Active Member

    May 8, 2010
    Just wondering what your application is. I recently had the identical situation with a transducer which was supplying a 4-20 ma sig to a VFD motor drive. The pump was a positive displacement type which caused a very jittery signal from the transducer. In this case, the VFD (an Emerson) could be programmed with a software version of a low pass filter, and this worked quite well.