In Honeywell Experion, particularly in Honeywell Control Builder, how do I have the system retain the last good PV value before a Bad PV (loss of PV signal or "NaN"). I need to retain the last good PV value and use that in my DACA or PIDA block. Kindly advise. You may contact me offline at [email protected]

Thanks,
dcsmec

 

> In Honeywell Experion, particularly in Honeywell Control Builder, how do I have the system retain the last good PV value
> before a Bad PV (loss of PV signal or "NaN"). I need to retain the last good PV value and use that in my DACA or PIDA block.

Change the 'PVCLAMPING' option from 'NOCLAMP' to CLAMP'.

 

> In Honeywell Experion, particularly in Honeywell Control Builder, how do I have the system retain the last good PV value before a
> Bad PV (loss of PV signal or "NaN"). I need to retain the last good PV value and use that in my DACA or PIDA block. Kindly advise.

Hi this would be my first response but I believe I can help with this. PVCLAMP will help for over range conditions, but if you want to store the last PV on loss off signal (say, the trx fuse is opened suddenly), you can try the following:

1) raw PV signal into a CHECKBAD logic block
2) also feed the raw PV signal into input 1 of a SIGSEL logic block
2) result of CHECKBAD block into the G input of the SIGSEL block
3) output of SIGSEL into a NUMERIC
4) tie the PV of the NUMERIC into back into input 2 of the SIGSEL

The PV of the NUMERIC block also acts as the last good PV value, so you can tie into whatever you need it for. When the raw PV goes bad, SIGSEL swaps over to the second input, which is the good PV stored in the NUMERIC. Just insure your CMs execute in the correct order.

hope it helps

 

This is easy. The DACA has a output pin (or parameter) daca.lastgoodpv. Instead of taking output from daca.pv, take it from daca.lastgoodpv.

regards,
tomsci