Frequently Asked Questions about the Tachometer

Currently using LG-9200/TM-3130. Measuring by attaching 25 small reflective stickers to a rotating body with a diameter of 60 mm. I would like to know the possible causes and solutions for the following issues. I am monitoring the analog output (0-10 V) waveform from the TM on a memory high recorder. The pulse count shows a waveform output at regular intervals, but the entire analog output waveform fluctuates up and down (with variations in amplitude).