Both the IR transmitter and transistor I use come from a TCRT5000. Noise is not coming from a faulty wire in my scope unfortunately, would have been an easy solution though

I have heard about a lock-in amplifier before, but have to do some reading to understand what it is they are exactly doing. Any suggestions on relatively easy to build circuits? Might be a good thing to try out.

Thanks,

 

Both the IR transmitter and transistor I use come from a TCRT5000. Noise is not coming from a faulty wire in my scope unfortunately, would have been an easy solution though

I have heard about a lock-in amplifier before, but have to do some reading to understand what it is they are exactly doing. Any suggestions on relatively easy to build circuits? Might be a good thing to try out.

Thanks,

If it is not a faulty ground clip, I am guessing the ground clip is too long (more then 3 or 4 inches) or poorly connected to ground in the circuit.

 

Think of a Lock-in as a synchronous detector. You have to have a periodic signal and know when the signal is present and when it isn't. Mechanical choppers for a light signal is a way of creating such a signal. The waveform is trapezoidal with a chopper.

With a digital DSP lock-in, you can actually read the n'th Fourier coefficient of the sine waves that make up the signal.