How do you choose the reference frequency when using a lock-in amplifier?
I want to measure the amount of lateral deflection of a laser reflected by a surface that will be oscillating very slightly. I'm going to modulate the laser at a set frequency, and send the trigger signal and the signal from a position-sensitive detector to the lock-in amplifier.
At the moment, I'm not sure how quickly the surface will be oscillating, or how much, hence this measurement. My first guess is to choose a reference frequency that is many times the rate that the surface will be oscillating (for instance, 100x), in order to ensure the lock-in detects the variation of the signal, but I don't know how to optimize this for a clean measurement.