The fluctuating motor voltage from the Diagnostics screen is perfectly normal. If the motor speed is steady at 100% and the analog test point is steady, then there is nothing wrong with your chopper motor.
However, the spiking of the analyzer is not normal. Let’s start investigating at the source, literally. Try peaking the signal strength of the IR source by adjusting the inlet and outlet mirrors. We have posted the instructions on one of our previous posts. If that doesn’t help, try replacing the IR source. Finally, try swapping out the pre-amplifier.
UPDATE: the problem was the pre-amplifier. You can see from their original graph, and at the beginning of the graph below, the trace was noisy, had occasional spikes and the auto-zero was erratic. After replacing the pre-amplifier, everything improved.
