Osilloscope to check encoder

buffalonymann

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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
 
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?
 
It would be a big help if you would post the model number
BEI as well as most manufactures make encoders with multiple output types
How you test them is different for each
Several outputs types are
Differential Line Drive
Push Pull sometimes referred to as totem pole output
Open Collector
Open Emitter
HTL
TTL
422 level output
Then you have different voltage levels for each
And don’t be confused with the input voltage it may not be the same as output.
Differential Line drive output dos not reference to ground it the polarity flip the input us looking at
ON would be A+ is Pos with respect to A- and OFF A+ is Neg with respect to A-
I have seen many encoders that have 24VDC supply with the output at 5 VDC
TTL is normally 5VDC but it can be higher
Some of the transistor outputs need a pull up or pull down resister or other external load others do not
You need to know all that information in order to know how to hook it up and how test it and of course what to look for in the test.

That doesn’t even go into resolvers (sometimes called phase angle resolvers)
Or Absolute encoders
You can’t tell what’s inside by looking at them you need the model number
There are many typed of encoders each has their own place in controls and they are not interchangeable

I know this sounds complicated but it is important to understand them.
 
For A+B+Z encoders I use this Saleae Logic - 8-Channel USB Logic Analyzer,not original but China clon for 10$....(for 5V encoders...for 24V You must use it with some resistos).....output see attachement...

Encoder.PNG
 
Encoder is BEI xh25d-ss-2500-abzc-28v/v-em

I am using Link Systems MSO-28 scope emulator. I understand I understand the technical aspects of a scope but still learning what settings I should use
 

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