getting velocity from edge cout

[struggling student]

i've connected up a incremental encoder to a SCB-68 acquisition box. i get the pulse couting ok and can produce a displacement time graph. when i tried to differentiate it to get velocity using the time domain i get a graph showing lots of peaks as if it has differentiated the time.  This is fine but when I tried to use the waveform measure the error is telling me the amplitude is zero. is this because i am using an edge count would i be better off using something else?

I have tried all sorts of things.

[johnsold]

First, the SCB-68 is just a connection interface. The actual data acquisition device is connected to the cable coming from the SCB-68 toward the computer, probably a PCI card inside the computer box.

Differentiation tends to enhance any noise or irregularity in the encoder signal. Some type of smoothing may help. Moving average filters or the Savitsky-Golay filter may be useful.

If you can post your VI with some typical data saved as default (we do not have your hardware), someone may be able to help.

Lynn