Extract Single Tone Information.vi configuration help

[Electro-Frog]

Hello.

I am trying to measure speed from a sensor that outputs the speed directly to frequency (i.e. 500 Hz = 500 RPM).
I am using the Scaled Window.vi with Hanning and the Extract Single Tone Information.vi to get the frequency.
I successfully measured to about 500 Hz with the default settings.
My range is from 0 to 2500 Hz.
The only settings I can find that seem to let me configure sampling is the approximate frequency and search (+/- % of Fsampl.)
These defualt to -1 and 5 respectively.
I assume this means no default frequency, or 0 and the sampling rate is 10000 (500 / 0.05).
I changed the approximate frequency to 1250 (my center frequency) and the percent to 12.5 (10000 / 1250 ).
This resulted in labView only reading one seemingly random value or not updating this measurement.
After putting -1 in the approximate frequency again, I was able to read values higher than 500, but they folded around 500 (i.e. aliasing).

How do I change the settings or use another vi to get the range that I need?
Thank you,
Electro-Frog

[mfitzsimons]

Increasing the sampe rate / per second will increase the range that the FFT will be calculated over.  Total samples doesn't make a difference iti s dependent on the rate of samples.  i was running at 10,000 per second and the FFT measure form 0 to 5,000 so I think it is sample rate / 2.  Just experienced this a few weeks ago so give it a try and let me know your results.

[Electro-Frog]

Thank you very much mfitzsimo…,

That did the trick. It has been so long since I changed the sampling rate, that I forgot it was there.
Apparently the Extract Single Tone Information does all the calculations for you, based off the sampling rate of course.
I bumped it up to 10000 samples/sec from 1000 (where the 500 folding came from) and I could read everything my function generator could put out.

Electro-Frog

[mfitzsimons]

A nifty piece of information that took me a bit to figure out.  Have Fun!