Encoder Testing

Hello All.

Is there an easy way of testing encoders that are still mounted on a machine in operation. I have been told that I can use a scope, but I have no idea how to go about it.

Thanks is advance.


Derek

I can help if you need. I'm just east of you.

Look at the control that the encoder feeds. Many counter cards, controllers, etc. have indicator LEDs. They should be blinking as the encoder rotates.

If you do not have such LEDs, or cannot get a response from them the encoder output could be weak, or the power supply low or failed.

Hook the ground clip of the scope lead to the common for the encoder power supply. Touch the tip onto the A, B, Z phase wires seperately. You should see a square wave as the encoder rotates. The voltage level of the square wave should be close to the encoder input voltage - typically 5 or 24V or 15V.
Unless the encoder is a differential (line driver) output. Then you should measure between the A and A/, B and B/, Z and Z/ wires.


RT

Scopes are great for this. Remember that the ground clips of the two channels are tied together internally and they are also tied to the ground prong of the 110 V outlet.

So be careful that you dont induce a loop by getting two different grounds in a ckt.

One way to get around this is to use a 3 to 2 adapter on the plug for the scope. Then remove the ground lead from channel 2 if you use it. This way you dont have to worry about more than one ground point in your circuit.

Another test, (less scientific) is a mechanical test. The shaft of the encoder should spin freely. If it feels like loose gravel when you turn it, that should alert you taht something is wrong. a gritty bearing or a shattered glass disk can give you that feel.

Thanks Rob.


BTW, did you find anyone to build your panel on Monday




Derek

Yes, there is a local guy in Port P that does regular work here; I got him called in.
Did you get your encoder checked?
Cheers.