DC filter for motor with shunt for oscilloscope

Discussion in 'General Electronics Chat' started by singular, Dec 19, 2009.

  1. singular

    Thread Starter New Member

    Dec 19, 2009
    conecting a oscilloscope to the shunt in a dc 3v motor circuit gives me to much noise in the graph, any idea in proper filter to use?

    I need to check the diference in force between the two parts of a non simetrical pulley and that is the way i feel easier to take the time, rpm, position, etc.

    In the same circuit I took a photocell to check through the B channel on the osciloscope the positions of the pulley and that is working perfect.

    Thanks for advice,

    Last edited: Dec 19, 2009
  2. Bernard


    Aug 7, 2008
    I would first add a .1 uF cap across motor; still to much hash?, add an RC filtar across " shunt", something like 1k ohm & 1.uF, measure across the .1uF.
  3. SgtWookie


    Jul 17, 2007
    Yep, you basically need a low-pass filter.
    But if the values of R and C are too large, it'll have a heck of a phase shift.

    This may very well be too much:


    but it's the general idea.
    Reducing R1 and C3 will reduce the shift.