Need Help!- ENCODER TEST

[MSGMachine]

I am trying to test some differential encoders that I have by waching the voltage per channel as I breath on the shaft(very sensitive).
I was expecting to see 2.5v high and .05v or so on the low for each channel (A+,A-,B+,B-,Z+,Z-). But some of these channels only changed from .07 to .08v while others went from .10v to 1.62v. I am assuming this is a bad encoder but I have no experiance with this, can someone fill me in.

[Al_The_Man]

The normal signal level is 0 to 5v square wave for differential driver.
The exception is some such as made by heidenhain and a few others that are either 1v or 11µA sine wave.
The other scenario is if they are open collector, but these are usually the exception for differential type.
Al.

[MSGMachine]

Thanks for the reply.
these are diff square wave line driver encoders
that is 0-5v for each signal (A+ and A- for ex.)right?

eather way i guess it's bad.

[Al_The_Man]

All signals should be 0 - 5v. The A- is just a complement of the A+ etc.
Al.

[Larken]

Try adding a 1K pullup resistor on each output. Do you have a scope ?

[MSGMachine]

I don't have a scope, just a volt meter.

[Al_The_Man]

You can detect the 0-5v pulses if you turn the shaft as SLOW as you possibly can.
Take a look at the chip markings if possible in the encoder, you can often tell this way if it has a standard differential driver that does not require a pull up.
Al.

[MSGMachine]

Some of these channels only changed from .07 to .08v while others went from .10v to 1.62v

[Al_The_Man]

You could try a 1k pull up to 5v as Larry suggested, just try one channel, it will tell you if the rest need it.
Apart from that it could be the low level sine wave type as I mentioned.
You could really need a 'scope to confirm this.
Al.