1771-VHSC issue

[asterof]

Have read most of these postings on this module
I got a new one for ya

One encoder with channel A wired to A1 and A2
IE Counter 0 and Counter 1 inputs
Unidirectional count
Module works fine, BTR/BTW very fast
Remember that all you are reading is internal registers
inside the module, so scan times are not so important

Now
Even though the same encoder is wired to two inputs
the counts on those two inputs becomes exponentially in
error from each other.

Shielded on one end only. 24 vdc power supply, regulated

any ideas

 

[kamenges]

Do you know which is correct? That is to say are you missing pulses or gaining pulses? Or are neither of them right? Are they really deviating exponentially or are they deviating linearly?

Keith

 

[asterof]

Counter 0 gains counts over Counter 1 and the longer they count
the greater the spread. neither of them would appear to be correct
based on the encoder PPR and the RPM. The cable is really good cable
twisted individually shielded cable, however if it was noise it should effect both counters as they share the same pulse train.

 

[rdrast]

How far are they deviating?
Are they both configured exactly the same?
It almost sounds like one is set to Quadrature X1, and one is Quadrature X4 or something similar.

Is the difference truly exponential? or is it linear? That is a huge thing.

 

[jac]

Have you put a scope on it? what does the waveform look like....?

 

[asterof]

No scope

I have not put a scope on it
I did check to see and make sure the modes were the same
However I will again double check that
What about cross talk between the inputs