Our monitor counts a retained PLC signal twice (Fairino FR5)

RachelBell0696 · 1 Sept 2026, 15:50 UTC

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RA
RachelBell0696
When our monitor reconnects, a completion signal retained from before the outage can be treated as a new completion. We're tracking part acceptance reporting with Fairino FR5 in a PLC-coordinated inspection bench, using a sample bracket. I'm trying to reconcile the signal with its job, without automatic resubmission or simply clearing the retained state.

12 replies

BE
BethBrown0933
Replying to RachelBell0696

@RachelBell0696 Does your trace show completion staying high through the outage? And does the application retain what it already consumed?

12 points
RA
RachelBell0696
Replying to BethBrown0933

The trace confirms completion remains asserted through the outage. Our application loses its consumed marker on restart, causing the first read to be interpreted as a fresh completion.

20 points
BE
BethBrown0933
Replying to RachelBell0696

Use an offline reconnect replay with persistent job state and match the retained completion before applying it. Making the consumed marker durable should prevent duplicate accounting.

13 points
CH
ChloeChen1179
Replying to BethBrown0933

Only if that marker identifies the right job. One persisted boolean could hide a genuinely new completion instead.

-7 points
BE
BethBrown0933
Replying to ChloeChen1179

@ChloeChen1179 Correct. I left out the important qualification: persist consumption against a matching job and attempt. If identity can't be established, leave the state unresolved.

8 points
RA
RachelBell0696
Replying to BethBrown0933

Would an explicit reconciliation phase help on reconnect, so the application doesn't treat its initial retained-state read as an ordinary new event?

8 points
BE
BethBrown0933
Replying to RachelBell0696

@RachelBell0696 Yes. Read the retained state, compare it with durable history and decide what it establishes. Reconnecting itself isn't evidence of new completion.

18 points
MA
MayaBell0649
Replying to BethBrown0933

On my monitor, reconnect reused the startup path and reset the last-seen value. Edge detection then invented an edge nobody had observed.

4 points
AD
AdaBrooks0825
Replying to MayaBell0649

Would ignoring the first high value fix that? It feels tempting, which probably means I'm missing something.

19 points
BE
BethBrown0933
Replying to AdaBrooks0825

It could discard a real unrecorded completion. Your first read is an observation to reconcile, not something to accept or ignore automatically.

20 points
RA
RachelBell0696
Replying to BethBrown0933

I've identified why this first read appears new, but our identity matching and durable reconciliation behaviour aren't fully established.

14 points
BE
BethBrown0933
Replying to RachelBell0696

That's useful progress: the repeated read is explained, and the matching and persistence work remains visible.

6 points

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