Created Date: November 03,2014

Created by: jonesjeremya

Have you tried doing the inch conversion to V400 (V400/R351.524824)?

MANY thanks for the suggestion!

I gave it a go and it gets my inch resolution down to .0078 "

I was hoping for .004 resolution or better, but I guess this is the limitation of the encoder PPR I chose for this application? I'm still a little foggy as to what is going on with the calculation behind the scenes. My only guess is that it's because I am using a 500 pulse encoder and it's forced to round up or down in order to reach a whole number?. I assume that a 1000 PPR encoder would put me at .0039 resolution?

Thanks again for the help, VERY MUCH appreciated!

Created Date: November 03,2014

Created by: jonesjeremya

Well, I thought I was moving on....not so fast.

So at a very low # of pulses I seem to have a resolution of about .004, but as I turn the encoder to generate pulses that would equal about 60 " of travel suddenly I only have resolution of about .500, the higher # of pulses, the worse the resolution gets.

For what it's worth, I still have the same resolution on my "millimeter " register.

I am lost as to why this is happening on the second register? All I need is a total of 6 digits for the HMI, XXX.XXX "

Perplexed!

Created Date: November 03,2014

Created by: bcarlton

Be sure not to overrun the 7 kHz limitation on the inputs.

But if the millimeter count is correct then the inch count should also.

How are you determining the resolution problem? Do you stop at some point and the two don't match?

Are you possibly looking at the results on successive scans of the program? The counter can count faster than the program can execute. A succeeding scan could happen after many pulses have passed depending on the input speed.

Created Date: November 03,2014

Created by: Shimmy

You should also check your setup. I'm not sure what the HSIO 500 encoder is but I am assuming it is a quad encoder. If so you may want to use mode 20 with quad 4x counting enabled. This should help your resolution (assuming you aren't exceeding the 7k bandwidth of the high speed inputs). If you aren't familiar with quad counting you essentially get 4 counts per pulse instead of just 1. Here is a link to the appendix for the 06 PLC for setting up the mode. Go to page 24 for mode 20.

http://www.automationdirect.com/static/manuals/d006userm/appxe.pdf

If it is not a quad encoder use mode 10. I'm curious what happens in mode 10 if you enable 4x counting. You may get double the resolution.

Created Date: November 03,2014

Created by: jonesjeremya

Thanks guys, here are the answers/responses:

I have attached screenshots of encoder pulse at 500, 501....It's way off at 20000. I'm most confused by the fact that my "millimeter " register remains accurate and doesn't get all goofy with the higher count.

I can't imagine why the "inch " register won't calculate properly. I think my math is close. Again, I can take the same expression to Excel and it's correct.

This is on a bench before mounting on the machine. I'm not getting confused by any real measurements, speeds, etc. I am turning the encoder slowly by hand and the counter which keeps up with the count shows 500 pulses for each full rev CW, and decreases by the same amount when turned CCW.

I am using both channels A/B of an absolute encoder so I get bidirectional counting which is required. I am set at mode 20. I am looking at still data while monitoring the calculation of my last hand movement of the encoder shaft

The math just doesn't add up :/

Thanks for the help!!