How to interpolate one signal to fit sample rate of another signal

[ACiDuser]

Hi all!

I have two signals. One is original with about 10k samples, duration - 1s. 

The second - is a demodulated signal almost the same as original but with about 200-500 samples.

To be able to compare two signals I should have samples for both signals at the same time. 

 Then I need to substract one signal from other to get deviation and calculate error.

 How can I interpolate second signal to get samples at the sime time that first signal has ?

Thanks in advance 

[Herbert]

I would say by doing what you ask: Interpolate using the interpolate function in the array category.

Herbert

[Coq_Rouge]

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Herbert wrote:

I would say by doing what you ask: Interpolate using the interpolate function in the array category.

Herbert

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The most used way of doing it I think you will find here http://en.wikipedia.org/wiki/Upsampling. But I think the interpolate idea is good to. If you need to insert more than one sample use the ramp pattern

I made something quick and dirty. Test it and see if you can use it. You have to do something about the missing samples at the end.

[ACiDuser]

Thanks, but I don't undestand what your example does.

It seems not what I wanted, as the timing of signals should remain unchanged - 1 second. Only increased number of samples

[ACiDuser]

I need something like in attached VI. But the problem left is - I can't determine where I lose the last value in array so I get incorrect graph for "Interpolated Signal 2"

[Coq_Rouge]

I am not sure I follow your dataflow now. If I sample a 10Hz sinus for 1 second with 200Hz I get 200 samples. If I sample the same sinus with 1KHz i get 1K samples. The FFT shows that the frequency is preserved during upsampling.

[ACiDuser]

What does "Samples" control do in your code?

[altenbach]

Have you tried the Align & Resample Express VI?

[ACiDuser]

Yes, and after that I get array of 990 elements not 1000. Which means Align & Resample functions does something wrong. Please see attached VI.

 Why after linear interpolation, when I compare signals -  I get continuously increasing deviation between two signals ? 😞

Message Edited by ACiDuser on 05-23-2009 01:54 PM

[ACiDuser]

It see it seems to be working, but I don't want to waste 6 hours of work. Maybe anyone see what I might did incorrect in changing signal sampling rate?