What is the difference between resample.vi, decimate.vi and the filter(FIR.VI)

[dec04009]

Hello, who will gfive me some advice about the difference between 

decimate, resample and the filter VI

For example, I have a signal and the sampling frequency is 2000Hz

If I want low pass the band from 0-1000Hz

I can decimate the signal with the coefficient 2, or I can also use the

FIR filter with the low pass function.

What is the differnet between the result? And what about the resample.VI

[devchander]

The FIR filter with low pass function, filters the input data using the set of FIR filter coefficients that are specified by window, sampling freq, low and high cutoff frequency and number of taps. The result will be an array of filtered samples

Where as in the decimate.vi, From the  input array, just those samples corresponding to the decimating factor set are selected and given as the output

For Ex: if you input an array of 100 samples and specify decimation factor as 2, only the 50 even samples at following array indices {0,2,4,6......,98} will be presented as the output.

Hope this helps

Regards

Dev

[Yann Falevoz]

Hello,

With the low pass filter, you'll keep the same number of points, but variation greater than the cut frequency will be remove.

With the resample vi, you'll change the sampling... The number of point will change (more or less) but the band with of your signal will be the same. The time step is changed. The value of each point is recalculate using interoplation.

The decimate vi will transform your array in n subarray. If the decimate vi size is 2, you'll obtain 2 subarray. In the first one you'll find all the points with an odd index and in the other all the points with an even index. Each subarray is equivalent to a particular resampling. The signal is the same, with a time step multiplied by the decimate vi size.

by!

[dec04009]

Many thanks for your clear reply!

This problem has confused me for a long time.