I'm attempting to examine the pulses from an encoder BEI. It has A+ A- B+ B- Z+ Z- PWR and GND. I connect the clip from probe to GND and the probe to A+ but not seeing the pulse
This is how my BEI works. A+ and B+ are offset by 90 degrees so you can tell which direction it is going. A- is an inverted version of A+. B- is an inverted version of B+.
Z+ is the home position, one pulse per revolution. Z- is the inverse of Z+
Do you have the correct voltage on the encoder? I have seen a 24V, a 10V and a 5V version.
I also need to pull the signals UP. So I have a 10V power supply through a 10K resistor to the A+ output. When the A+ is not being driven low by the encoder, it shows about 9V. It drops to 0.4V when the encoder drives A+ to ground.
When I was playing around with the encoder I put 2 10K resistors in series, from 10V to 0V. And I connected the encoder A+ signal to the middle of the 2 resistors and monitored the voltage. That's how I figured out that I needed a pull-up resistor. When A+ was not driven it was at 5V. When it was driven it went to 0.4V.
I don't know how well you know your scope, so I mention these as part of what I do with my crappy old scope:
- set the trigger to auto, rising edge
- set the threshold about half the expected voltage
- if you have a calibrate signal on the scope, you can use it to make sure that your trigger works, and that the voltage/time is set to something reasonable
I use a cordless drill to spin the encoder, so I can change the speed and have the pulses as wide as I need them to be for checking out the pulse train. Did I mention it was a crappy scope?