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Consider the signal of e.g. a photodiode or a spectrometer, where a dark measurement has been taken to account for baseline noise. The signal we want to measure is quite weak, so we need a decently long integration time to almost saturate the device, lets say 1 second for the sake of simplicity. This gives us a reading every full second.

What if instead we used a 200 or 500 ms integration time and averaged 5 or 2 measurements, respectively, into 1 reading. Are these averaged measurements objectively better or worse, as both read out the signal every full second? Worded differently, one could ask if it is a good idea to always go near saturation if the time allows for it, i.e., if the measured process is static or very slow?

John Doe
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  • Please specify what "saturation" is in this case. – Max Aug 30 '23 at 07:12
  • In this case, I mean that the sensor is giving out a digital signal of "counts" up to 2^16 for certain wavelength bins, and saturation is reached when this value is hit or exceeded. If you consider a laser emission line with ever increasing power, at saturation you would start to "cut off" the top and get a flat plateau peak. In practice, I try to stay at around 80% of max. signal. – John Doe Aug 30 '23 at 07:33
  • Ok, so the sensor itself is integrating. Then the answer depends on what you want to measure. Just detection (signal or no signal) or actual measuring (does the actual count matter?). If the former, go for long integration time, if the latter, find a good trade off between SNR and minimal chance of saturation. – Max Aug 30 '23 at 08:18
  • I do actual measuring. But that's the question: of course I can average more and increase my SNR, but given a fixed, limited time per measurement, I wonder if it is better to maximize integration time or to go lower with integration time and average a few times more. – John Doe Aug 30 '23 at 11:33
  • If your noisefloor is stationary and you take the arithmetic mean, there is no difference between the two. – Max Aug 30 '23 at 14:04
  • That was my intuition, but I wanted to get a second opinion. If you could elaborate your comments into a full answer I will accept it. Ideally you could also describe a scenario where the two scenarios are NOT the same? – John Doe Aug 30 '23 at 14:39
  • Please see this highly detailed answer: https://dsp.stackexchange.com/a/87403/41790. It all depends on the relevant noise(s). – Ed V Aug 31 '23 at 01:37
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    Ed V postet a link to an indeed highly detailed answer by Dan Boschen. I don't wanna post an answer here, just give Dan's an upvote. – Max Aug 31 '23 at 06:16
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    That's indeed a very useful answer! Upvoted Dan's answer. – John Doe Aug 31 '23 at 07:16

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