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David Notebook: Difference between revisions
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I've still been having trouble getting the lock-in readings to match the values I think it should have, whether I give it a signal from a function generator or from the photodiode. A 2 volt peak-to-peak amplitude square wave should give a reading of .9V on the lock-in (4/(π*2^.5) and an output of 9 V for the extra factor of 10. Page 31 in the manual gives this
I also noticed that I am not getting perfect square waves from the laser/chopper/photodiode combo. While it works well at low frequencies around 40 Hz, at 500 Hz where I was running it the waves are distorted. This is likely because the response time of the photodiode is not fast enough. This should not affect optimization procedures, but it does mean that the Fourier component at 500 Hz does not have an amplitude factor of 4/π. I will either need to run the chopper slower if there is not too much noise at lower frequencies, or calculate a better value for the pre-factor before converting to an absolute power value for the 633 beam.
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