Encoder Configuration Confusion

[John_R]

Hey All,

I've been playing around with an encoder connected to a V200-18-E3XB.
This is a 600 ppr A-B encoder, configured in X4 mode (which I believe gives me a 2400 ppr count as it counts the rise/fall of both channels, correct me please if this is wrong)..

I have assigned MI 17 for the frequency measurement of said encoder.

The number I see in MI 17 matches the speed of the shaft I am connected to.

All Good... But Why?

No where in my code have I specified 600 ppr (X4 2400 ppr), and I assumed somewhere I would have to scale/linear MI 17 into a number that matches my real speed.

What am I missing? How can it be correct if I have not declared the actual ppr of the encoder somewhere in my code???

Assigning the Frequency Measurement option gives the choice of 100ms,500ms, or 1000ms, does this come into play?
I just assumed that was the update time..

JohnR

 

[kratmel]

If you use 4x encoder and  frequency measurement - you must use frequency/4  for real speed calculation. 

For RPM ---- frequency/240/10 need to be used. (240=4*60)

Then 2400ppr generate correct speed if frequency is in 0.1Hz

[John_R]

40 minutes ago, kratmel said:

If you use 4x encoder and  frequency measurement - you must use frequency/4  for real speed calculation. 

Well Kratmel, thank you for the reply, but I'm not following what you are saying...

I am doing no calculations, but yet my assigned MI for frequency measurement (here MI 17) is giving me a number that closely matches the speed (rpm) displayed by an existing speed display.

Hence my confusion, as like I said, nowhere in the encoder config. or code do I specify the ppr of the encoder, but yet it is correct...

[kratmel]

I'm not saying you have code to handle the value.

I was looking for a simple explanation that the number you got is correct.

You just connected the encoder for 600 pulses per revolution.

And the "hidden" math itself is that the received real speed "automatically" turns out as it should because you chose a 4x type encoder.

That is, I try to explain your number 2400 that you mentioned.

[John_R]

So you are saying that the default Vision conversion from Frequency Measurement to MI just happens to be 600 ppm (or 2400 with X4)?

If I had used any other ppr encoder I would have to do some math, but 600 ppm is correct.

[kratmel]

16 minutes ago, John_R said:

If I had used any other ppr encoder I would have to do some math, but 600 ppm is correct.

Yes. If result without math is correct - you solve your task. And maybe this ppr is standard for old type counters where only logic ic present. 

I have in my lab encoder Sick with programmed ppr (1-8096ppr possible). I use it for replace non standard encoder in application like old grinding machine, lathe...

Last time encoder with 216ppr replaced.

 

[AlexUT]

Hi,

1. Schaft Encoder in most of cases generate 2 series of pulses, shifted by 90 degree .

2. Encoder itself does not know how you configure your HSC - in this case it is PLC.

3. Dependent of selected configuration PLC make an internal processing of both signals and make proper calculation.

4. Position calculation precision and direction sense precision is better at x4 (4x), as more signals are used.

5. If you connect schaft encoder to Arduino, or other Microcontroller - you have to process and calculate everything by program.