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Measure Frequency and Amplitude from Analog Signal

Seeing the milli "m" is a bad sign that things aren't working then. :smileytongue:

 
--- I'm afraid so. 
 

Would it be better to attach a DBL array than building my own waveform or would both methods be the same?

 

 

--- Don't know that there is a "better" way.  The waveform is a bit cleaner, since everything is in one wire, and the answers come directly out, but it's not a big deal either way. 

 
 
There must be something you're missing; it's just not that complicated.  Either post your code so I can see it, or take a look at this pic:
 
With a sample rate of 1000, the "dT" is 1/1000 second.
With a sample rate of 1000, then 2000 samples with 36 cycles is equal to 18 Hz.
If you build a waveform and analyze it, you get 1.5 V at 18 Hz.
If you feed the DBL array directly, you must mutiply the frequency detected by the sample rate, and you get 1.5 V at 18 Hz.
 
Notice the coercion dot on the lower EXTRACT function.  That means it is converting the [DBL] array you give it to a waveform for internal use.  Probably not a huge deal, but that takes time.
 
If you make it work on computer generated data,  but it doesn't work on your acquired data, then something's wrong with your acquisition.
For diagnostic purposes, graph your data. Display the dT you're building the waveform with.  Display the waveform before it goes to the EXTRACT function.
 
LabVIEW's great for that - just plop an indicator at any point in the chain and see what shows up.  Use PROBEs for shorter-term peeking around. 
 
 
 
 
Tone.PNG 

Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com


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Blog for (mostly LabVIEW) programmers: Tips And Tricks

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I tried what you said and the computer generated waveform works fine, but the gathered data does not.

We did a bit more research on the device we were using and discovered that the sampling rate of the device we're passing data through is severely limiting the amount of data passed through, rendering any attempt useless above a certain frequency. And of course that certain frequency is way, way too low for our usage.

So, yeah. Thanks for the help Steve. I'm sure it would've worked with the right hardware. 🙂

Cheers
-Tanner
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OK, this verifies an old saying of mine:

"Sometimes the software isn't lying". 

 

 

Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com


LinkedIn

Blog for (mostly LabVIEW) programmers: Tips And Tricks

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how to do thiss frequency measurement on fpga?

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How to measure the frequency of incoming analog signal into the FPGA from a photo detector?Is this possible??

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Hi Sunu,

 

I just replied to you on your original post here:

http://forums.ni.com/t5/LabVIEW/FPGA-analog-input-frequency-measurement/m-p/2631249

 

 

Joey S.
Senior Product Manager, Software
National Instruments
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