Best PLC Wiring

[rdrast]

In addition to the comments above, if you have unused analog input's on the same PLC card, physically short them to ground.

Sometimes unused adjacent channels can create some nasty A/D conversions.

 

[mordred]

good point RDast best to avoid free floating analog inputs

 

[rdrast]

good point RDast best to avoid free floating analog inputs

Been bitten by that before

Another 'wise practice' that I've adopted, is to put a parallel resistor directly across any analog voltage inputs, something high, 47k or so, just to make sure that if the field wiring becomes disconnected, nothing unexpected happens.

Got bitten by that once too, and had a line go from 400fpm forward to 400fpm backwards, when a third party vendor pulled a card out of his unit. It wasn't pretty.