Experimental Physics and
Industrial Control System

"Schoeneburg, Bernd" <[email protected]> · Mon, 16 Feb 2009 17:00:21 +0100

Hello Steve,

I like your idea. Your sentence "do not raise an alarm unless there are

ANUM excursions outside HYST in ADLY seconds" must be extended by "or

the excursion is stable during ADLY seconds", I think. ANUM=0 should be

handled like infinite. If STAT==NO_ALARM and the alarm condition starts

to change between HIGH and HIHI, what should happen? I think after ADLY

seconds the alarm HIGH should be sent (the lower level if HSV < HHSV).

But what to do if the severities of changing alarms are the same?

Another thing: Digital records would also benefit from this mechanism

although they have no HYST.

- Bernd

Steve Lewis schrieb:

At 9:03 PM +0100 2009/02/15, Bernd Schoeneburg wrote:

/Hi all,/

/I would like to announce and discuss some ideas for base

modifications. These are in detail:/

*3. Alarm Delay Field in all Records*

Beside the alarm limits we have a "HYST" in the analog records. Why

not also a "DLY" (delay). Some values are very unstable and have some

noise or over-swing. So a short time over/under the limit should be

allowed sometimes. Implementing this in the ioc has two advantages:

1.:It is analog to "HYST" which is a value-related hysteresis. "DLY"

is a time-related hysteresis. 2.:Sending a lot of good/no-good

messages to the clients could be avoided. This change is not so easy,

many things must be considered.

I would call it ADLY ("alarm delay'). And I suggest you use this new

field and another new one, ANUM ("alarm number"), to implement this

just the way ALH now does: do not raise an alarm unless there are ANUM

excursions outside HYST in ADLY seconds. I agree that it is good to

push this functionality into the record because: (a) it reduces CA

traffic; (b) keeps this vital information in the database which is the

responsibility of the IOC developer, rather than with the possibly

multiple instance and maintainers of ALH or other alarm clients. In

particular, GUIs will now benefit.

One disadvantage: it hides the behavior of the device: how do you know

whether the underlying, suppressed alarms are getting better or worse?

How would you know to adjust the hysteresis parameters? As you say,

"many things must be considered."

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System