find time shift between two signal from measurement file to find velocity

[GerdW]

Ha khalid,

set the values shown in your CHART to default and save the VI. Then attach the VI…

[khalid.elserfy]

Hi GerdW

i have save data in graph as default data

thanks a lot

regards

khalid

[GerdW]

Hi khalid,

that's what I expected before:

- Your signals seems to be very noise.

- When zooming in you see some "spikes" on both signals - at exactly the same samples/time…

So I would conclude: there is no delay…

Again I repeat my question: What is the EXPECTED delay between both signals?

This is what I had in mind when I made the suggestion to crosscorrelate two signals:

(I faked the signal using a function from signal generation palette.)

[khalid.elserfy]

the two lasers are 2 mm apart , so i assume that there has to be time delay between the signals ,so from the peak of Rxy function i can get the delay between the two signals 

[daveTW]

I know nothing about your used measuring principle, but what I see from the zoomed-in-graph Gerd posted (first graph in post 13) you have a sample rate of 100 kHz (five datapoints between major ticks). This is a cycle time of 10^-5 s.

The delay for a light signal with a velocity of aprox. 3*10^6 m/s is for a distance of 0,002m around 6,67 * 10^-10 s. This is far away from your sampling time.

Could this be the reason, that there is no delay to see?