Experimental Physics and
Industrial Control System

Hi,

 

Yesterday I was presented with a case that puzzles me. I thought I understand the behavior of alarms but it seems that I do not.

 

One (ai, “Soft Channel”) record in our system seems to be stuck in alarm state. See below for what CA and PVA report.

 

The record reports a MINOR alarm severity, even if the HIGH is set at 30 and the value is below (at 27.96).

The record gets its input from another record, so I thought that maybe the alarm is propagated from there, but the input link is set to NMS.

And, the origin record is not in an alarm state so that would be odd anyway.

 

What am I missing here?

 

(One interesting observation is that pvget -v lists severities as null, although they are set (for sure.) HSV is set to MINOR (1).

EPICS version in this case is 7.0.6.1, but I see this with 7.0.7 as well. I do not think that this is related to the alarm behavior though.)

 

The records do not latch alarm states, do they? Or have I been wrong all these years? (I tried some other records in a soft IOC and they behaved as I would expect.)

 

What is the purpose of the ACKS and ACKT fields (if the explanation would be too long to write here, I can try to figure out from the source code…)

I have read what the record documentation says, but it does not help me to understand how these are intended to be used.

(Just for curiosity, ACKS=INVALID and ACKT=YES for that record.)

 

Is there an explanation for this, or any ideas where to look at?

 

Timo

 

--

(epics) timokorhonen@nxnode-06:~$ caget -a DTL-010:EMR-TT-028:Temp

DTL-010:EMR-TT-028:Temp        2023-06-16 09:09:44.009138 27.96 HIGH MINOR

(epics) timokorhonen@nxnode-06:~$ pvget DTL-010:EMR-TT-028:Temp

DTL-010:EMR-TT-028:Temp 2023-06-16 09:12:21.929  27.94 MINOR DEVICE HIGH

(epics) timokorhonen@nxnode-06:~$ pvget -v DTL-010:EMR-TT-028:Temp

DTL-010:EMR-TT-028:Temp epics:nt/NTScalar:1.0

    double value 27.96

    alarm_t alarm MINOR DEVICE HIGH

        int severity 1

        int status 1

        string message HIGH

    structure timeStamp

        long secondsPastEpoch 1686899551

        int nanoseconds 309940000

        int userTag 0

    structure display

        double limitLow 10

        double limitHigh 150

        string description "Temperature DTL-010 Tank, Location 028"

        string units degC

        int precision 0

        enum_t form (0) Default

            int index 0

            string[] choices [Default, String, Binary, Decimal, Hex, Exponential, Engineering]

    control_t control

        double limitLow 10

        double limitHigh 150

        double minStep 0

    valueAlarm_t valueAlarm

        boolean active false

        double lowAlarmLimit nan

        double lowWarningLimit nan

        double highWarningLimit 30

        double highAlarmLimit 50

        int lowAlarmSeverity 0

        int lowWarningSeverity 0

        int highWarningSeverity 0

        int highAlarmSeverity 0

        byte hysteresis 0