error 20020 with digital FIR filter

[Boris8135]

Hello
I am acquiring a signal from incremental encoder. I should receive a square signal, but there is a lot of noise. When I try to use the digital FIR filter a get an 20020 error. I know that it has something to do with fc frequency but I just don't know how to implement this into my vi.
Could someone explain this to me..

Boris

[Pakman]

Hi Boris,

Since you're passing in a 1D array of Y values to the signal input of the Digital FIR Filter, dt is set to 1.  This implies that your sample frequency is 1 Hz, violating the requirement of the cutoff frequency (Fc) being less than or equal to half the sample frequency (Fs).  Thus, you should use the "Build Waveform" primitive to modify dt to equal 1/Fs.  Feed this new waveform into the Digital FIR Filter.vi.  Refer to my attached VI.

What are you trying to accomplish with acquiring the analog signal of the incremental encoder?  Perhaps you can avoid the whole noise issue by connecting it to a counter?

[Boris8135]

Thank yu on your reply Pakman. You were most helpful. I am trying to acquire the signals from encoder so that I can see how they change with the rpm.

Regards
Boris

[Pakman]

How are you using the encoder?  Are you measuring RPM or angular motion based on RPM?

[Boris8135]

I am trying to measure the signal from the encoder with the voltage from the winding of the motor and how the two signals change with rpm.
Regards
Boris

[Pakman]

Hi Boris,

Did the Digital FIR Filter allow you to read the signal successfully, or are you still trying to get your application up and running?  Typically, incremental encoders are used to measure angular motion.  For example, they can determine which direction and how fast a shaft is rotating.  Is that what you're trying to do?  What data acquisition (DAQ) card do you have?

[Boris8135]

Yes, the problem is solved. Thank you for your help

Regards
Boris