BAD PV option in Contrologix

asim_rana · Apr 26, 2006

Dear Expert

We are using Contrologix ver 13 .Our Client wants to have "BAD PV" option. Now how to do it.

As I tried to use "Underage & Over range" bits but Underage becomes high only if signal is 0 & Overage only if it is 21.If signal is suppose 3ma then it’s a bad PV signal but under range bit is not set even I had select min signal to 4 ma in card properties. So how to get it.

Mostly I have also seen this Bad PV option in Honeywell DCS so plz let me know that is there any way to do it in Contrologix

Regards

Muhammad Asim Khan

pumpkins · Apr 27, 2006

You can use simple maths in a CPT block or similar to check either the raw PV value or scaled engineering PV (based on the scaling parameters) to determine if the PV is bad.

For example, if the engineering scaling is 4 psi to 20 psi and you're reading a value of 3 psi then this would equate to a 3mA signal. Just trigger the "Bad PV" alarm on a signal equal to or below this value, and equally on a "21 psi" or above condition.

You can have this block of logic in a "user fuctions" routine or similar, and just include it in all your programs for an instant "bad PV checker".

BAD PV option in Contrologix

asim_rana

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pumpkins

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