optical encoder channel question

[GSR]

I know there are channel A, B (maybe also Z) in a regular optical encoder. I just have a encoder card which say it is for Phase A+, A- , B+, B-. I guess Phase A = Channel A, but what is the + and - mean???

[crelf]

I know there are channel A, B (maybe also Z) in a regular optical encoder. I just have a encoder card which say it is for Phase A+, A- , B+, B-. I guess Phase A = Channel A, but what is the + and - mean???

The channels are usually isolated differential so the + is the positive side and - is the negative side of the signal.

[EricLarsen]

The channels are usually isolated differential so the + is the positive side and - is the negative side of the signal.

Most encoders are differential and will be labeled A+, A-, B+, B-. Some encoders are single ended and are usually labeled A, B, and Gnd (or something like that). In that case, you would hook A to A+, B to B+, and Gnd to both A- and B-. If you truly have a single ended encoder, you might check with the manufacturer to see how they recommend hook up.

Disclaimer: Hooking single ended encoders into differential inputs doesn't always work and is usually not recommend by the encoder card manufacturer. But I've done it a few times and it's never burst into flames.

[crelf]

In that case, you would hook A to A+, B to B+, and Gnd to both A- and B-.

Right, and the same goes for the Z+ and Z- if you care about absolute measurements.

[Daryl]

I know there are channel A, B (maybe also Z) in a regular optical encoder. I just have a encoder card which say it is for Phase A+, A- , B+, B-. I guess Phase A = Channel A, but what is the + and - mean???

In addition to all the great responses so far, if you are using an optical encoder in a high vibration environment, you may need to put a filter on it if you get some bleed through on channels A and B.

[EricLarsen]

if you are using an optical encoder in a high vibration environment, you may need to put a filter on it if you get some bleed through on channels A and B.

Just out of curiosity, what kinds of filters have you found to be effective for this? I've had this problem before and never really came up with a satisfactory solution.

[Daryl]

Just out of curiosity, what kinds of filters have you found to be effective for this? I've had this problem before and never really came up with a satisfactory solution.

I'll have to check if I have any left and get back to you. Its been a while since I have had to deal with this so I cant remember off the top of my head. All I remember is I used something in a 8 pin DIP configuration that seemed to work well.