Re: AlarmHandler - filtering vs. HYST

[Maren Purves <m.purves@jach.hawaii.edu>]

On Fri, 14 Apr 2006, Brian McAllister wrote:

> [ minor rant follows ]
>
> I also believe that alarm limits, especially MINOR alarms, should be
> influenced by operational reality as well as engineering design.  If the
> normal value of an analog input is close enough to an alarm limit to
> generate alarms when no action is actually required, that limit should
> probably be changed.
>
> Based on personal experience I can state that any significant number of
> "nuisance" alarms will lead to users becoming less reactive to real alarms.
>
> We were having enough issues with operators silencing ALH "forever" (so
> they wouldn't be annoyed by "false" alarms) that I modified ALH to put a
> black border around the button on the screen so you could tell it was
> silenced without opening the alarm window.

Brian,

while I agree in principle, here follows another one of Maren's
"it depends" posts:

We have some alarm handlers that are run up "silenced forever".
In fact, most of ours are. All we want from them is an email
notification that something bad has happened.

We do occasionally have alarms that recover by themselves
without the alarm limit being anywhere near normal operational
limits: we do sometimes have powerouts here. The IOCs and
equipment continue running on their UPS(s) whereas the
compressor/chillers hat keep the instruments cold trip.
Some of them will come back on when the power does and the
instruments will cool back down by themselves, some of them
need resetting. Needless to say, it isn't always possible,
e.g. in a snowstorm, to get to the equipment to reset it
(in which case we of course also don't care whether the
alarm handler beeps as there won't be anybody in the dome).
We need to know there's a problem so that we can at least
monitor it remotely, or more often, do something about it.

- We have in one case of a non-EPICS 'hovering' alarm
(wind speed) made the alarm limit settable by the operator.
If they have already closed the dome they don't need the
beeping, but before they close the frequency of gusts
above the alarm limit will have some influence on what they
do with it. -


Aloha,

Maren