PV Standard ACK ALL problem

naegely · Jul 25, 2011

I have a PanelView standard application that uses tag N15:71 for the alarm acknowledge tag. The acknowledge all value is 300, and the hold time selected is 1000 mS.

There is a rung in the PLC program that moves a value of zero to B16:0 when the value of N15:71 equals 300. This all normally works as I expect, when the acknowledge all button is pushed, N15:71 takes a value of 300 for 1 second and then reverts to 0.

However, twice last week, (on 2 separate but identical machines), I observed the value of N15:71 remaining 300 indefinitely while no buttons were pushed. The result of this was that operators were not getting any alarm notifications. Once I cleared the value manually, it went back to operating as expected.

There is nothing else in the program that changes the value of N15:71. Has anyone seen this issue before? The PV is a 2711-T10C8 (PV1000 Touch Color), FRN 4.0

Thanks for any input,

Rob

Mickey · Jul 25, 2011

Yes, I don't trust HMI's or SCADA systems to complete the job. So I usually take care of the problem in the PLC. In your case after the move instruction for B16:0 put a clear instruction to clear N15:17.

naegely · Jul 25, 2011

Thanks Mickey, I'm afraid I'm going to have to do something like that. The problem is there are about 40 machines, all governed by change control procedures, so it's gonna be a headache.

Thanks again for the reply,

Rob

Ken Roach · Jul 25, 2011

This could also be an instance of your DH+ network signal degrading.

The PanelView sent both the "Set to 300" and the "Reset to zero" messages, but the controller didn't receive the second one. Start examining the network for signal quality and error counters.

robo77 · Jul 25, 2011

I'm with Mickey I use the PV ack to latch a bit for a period and unlatch it after a time frame I like.
This way I can use that same latch for other ack bits from remotes..

rdrast · Jul 26, 2011

robo77 said:
I'm with Mickey I use the PV ack to latch a bit for a period and unlatch it after a time frame I like.
This way I can use that same latch for other ack bits from remotes..

This, all the way, everywhere. PV+ terminals here are the absolute worse offenders for failing to reset momentary bits and things. Only use them to latch something on, and reset it in something reliable, like a PLC.

PV Standard ACK ALL problem

naegely

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Mickey

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robo77

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rdrast

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