Filtering High Frequency Noise

Discussion in 'General Electronics Chat' started by skybox, Apr 24, 2009.

  1. skybox

    Thread Starter Active Member

    Mar 2, 2009
    Hi Guys,

    Here is a little information on a project I am working now. I have a sensor that outputs a pulse depending on the amount of fluid running through it. The higher the flow rate, the higher the pulse it puts out. I hooked up an oscilloscope on the sensor and it is a standard high low voltage (square wave)with a frequency of about 20 Hz. The problem is that a VFD (variable frequency drive) must be running when the system is running and this generates a ton of noise. The sensor is actually going in to a DAQ so I can get data into Labview and instead of Labview reading the 20 Hz signal, it reads a frequency of 1k - 1 Mhz because of the noise coming from the VFD. With the VFD not running, Labview reads the 20 Hz signal just fine.

    Should I just try to figure out this issue on the software side or can I implement some filter to get my 20Hz signal out?

    Thanks in advance!
  2. bertus


    Apr 5, 2008

    You could try to make a low pass filter.
    You should look what frequencies are of importance.
    Is the powersupplypoint near the sensor decoupled?
    You could try to feed the sensor through a choke with a capacitor accross the powersupplypoints of the sensor.