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Time jumps while measuring light frequency

I used a photidiode and Labview to record light frequencies from a helium-neon laser, but the program has been having large jumps in time. When we convert the data into a CSV file it will show times around 0-1 seconds, then jump to 3, then to negative 2. I've tried adjusting the rate it takes samples, but this hasn't helped. Does anyone know why it is doing this, and how it might be repaired?

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You will need to give us more information. Please post your VI. Run it and make current values default then save it again. That way we can see your values. Also post a typical CSV file (or a small subset if the files are large). 

 

What do you mean by light frequencies? HeNe lasers typically have a output at ~628 nm, I think. The frequency of that light can easily be calculated but I doubt any photodiode can respond that fast. And even if it could there is no counter which can directly measure that frequency. So what are you actually measuring? Is something modulating the amplitude of the laser light?

 

Lynn

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@mmoomin wrote:

I used a photidiode and Labview to record light frequencies from a helium-neon laser, but the program has been having large jumps in time. When we convert the data into a CSV file it will show times around 0-1 seconds, then jump to 3, then to negative 2. I've tried adjusting the rate it takes samples, but this hasn't helped. Does anyone know why it is doing this, and how it might be repaired?


Of course not. The only thing you've told us about your LabVIEW code is that you used it. Please post your VI, ideally a stripped down version which still shows the issue.

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Also please describe your hardware and input signal level and shape.

If you are measuring with TTL digital device, photodiode output is not always ideal for them. Connect scope with high (at least 1M impedance) in parallel with your device to get correct shape. 

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