Testing and Cause of Failure for Encoders and Hall Effect sensors

[TimCraig]

I'm working through an encoder problem now. The support guy at US Digital suggested that lacking a scope, you can power the encoder and use a digital voltmeter to check the output between the output pins and ground. For their model he said it should vary between 0 and >=2.5 volts as you turn it. Obviously, you can't turn the shaft too quickly or the DVM will not have time to settle. (Makes you wonder if an analog meter might react better) I tried this and couldn't see anything on the B channel which was easiest for me to tap. In my case, I'm absolutely sure it's the encoder because I have two, one on each transmission, and simply moved the cable from the known good one to the suspect one and got bupkus.

As an aside, I was trying to test just the encoder unit out of the robot since I thought it would be easier. I slid a sheet of paper into the slot and saw nothing. However, the support guy said the HEDS detector they use will only register the lines on the disk and not show the paper. I'm also a mechanical also so I'm not up on how this works. You'd think breaking the beam is breaking the beam.

When I get around to it, I'm going to have to build a test connector to make some of these tests easy.