Daba,
Thank you for replying.
In the past, I have always done diagnostics in the program for the relay by comparing the commanded output to the feedback signal of a normally open contact on the relay. If the rapid self testing occurs while the input is ON and the relay is energized, wouldn't this be be the same? The diagnostics in the program would check both states of the relay. This always seemed fine but I want to use the GuardLogix input diagnostics properly.
Maybe you are saying that by using normally open contacts, the relay would have to be energized first, feedback contacts close, then the fault would be detected and the relay would need to be shut off. When using the normally closed contacts, you would never have to energize the relay because you would already know the input is not capable of going LOW. Does this sound right?