lock in amplifier for IR LED and Photo darlington

[FvM]

In case of the shown waveform, it's hard to determine if the synchronous demodulator is working at all. It may have problems because the reference signal is unipolar instead of bipolar. And we would preferably AC couple the demodulator input signal (making it DC free) to remove the strong carrier frequent output component. The average value after the filter won't change this way but the ripple can be reduced.

 

[KlausST]

Hi,

Usually you need a low pass filter.

The filter depends on:
* what ADC resolution you have/need
* how often you want anew measurement value

Klaus