Two questions

[plc_user]

Hello support,

I have some questions.

1. What happens when the encoder inputs (MD Series) are pulsed faster than 10khz in quadrature mode?  1a.  Does it still count? 1b.  Stop counting. 1c. Get a random count?

2.  On the analog inputs, should we ground the unused inputs?


Thanks in advance and as always thank you for a great product.

[support]

1) Yes, if the incoming frequency is way higher than 10KHz then there will likely be missing count.

2) Grounding of unused analog input is optional. It is not necessary if you don't read the ADC value using ADC(n) command therefore the ADC channel will not appear to be reading a random number.

[plc_user]

Not to be a smarty pants, I just was wondering if this post: http://www.tri-plc.com/yabbse/index.php?board=1;action=display;threadid=1292;start=msg4001#msg4001  negates your response?  This has me alarmed because I have the other analog inputs floating and I do get some dither on the analog input that I am using with a filtering algorithm in the software.

As for the encoder question!  In your opinion can "cross-talk" occur at 10khz? between the encoder pins or the wire connected to them?


Any thoughts would be greatly appreciated.

[support]

In that post, the reader actually executes the ADC(n) on the unconnected ADC channel and therefore he will see readings that floats towards the pin that has active connection. If you don't execute the ADC(n) function on channel n that is not used then there will be no reading at these pins. If you feel more comfortable you can always ground the unused ADC inputs to ensure that they are not floating.

So far we have no report of the crosstalk between of high speed counter signals on the PLC input. But if you have signals that are bundled together in your wiring then cross talk could happen if there are high power electromagnetic field presence.