measure period of a pulse train

[Peter42]

I would like to measure the period of a pulse train.  Is there an example vi available without using a counter (hardware)?  Also there is low frequency modulation on the wave train.  Is there a way to filter out the low frequency components?

Peter Liu

[Luke_G]

Hi Peter,

I recommend that you take a look at the "Pulse Measurements" function in the "Waveform Measurements" sub-palette. You could use any analog input example, such as "Acq&Graph Voltage - Int Clk". Just wire the data output from the read function to the Pulse Measurements function.

As for filtering the low-frequency content, can you describe the nature of your signal? Is the low frequency content the same amplitude as the high frequency content? There is a palette of filtering functions under Signal Processing, however I'm not sure if they will give you the effect that you want. If you could describe what your signal looks like and what you need to do with it, we could provide a more specific suggestion.

Thanks,

Message Edited by Luke G on 05-31-2007 05:58 PM

[Peter42]

Thanks.  That was exactly what I used by putting that vi in a "for" loop and got all the periods of cycle numbers 1 to N and then get the mean period from the measurements.  As far as the low frequency component is concerned, it causes the separation of the individual pulses to vary slighly.  What I would like to do is to filter out that low frequency.  Perhaps when I use a time series many times longer that the period of the low frequency component, it will be averaged out from the mean period.

[Luke_G]

Hi Peter,
Gathering extra data and averaging over time is exactly what I would do to remove the effects of the low frequency noise.
Good Luck!