RE: Update behavior of camonitor

[Žiga Oven via Tech-talk <tech-talk at aps.anl.gov>]

Hi Dennis,

Most records will only send out a monitor event when the value changes. 
Certain records have dedicated monitor parameter fields such as MDEL (ai record) or MPST (stringin or waveform record).

Here is example from Component Reference Manual for AI record.

------------------------------------------
Monitor Parameters
These parameters are used to determine when to send monitors placed on the VAL field. The monitors are sent when the current value exceeds the last transmitted value by the appropriate deadband. If these fields are set to zero, a monitor will be triggered every time the value changes; if set to -1, a monitor will be sent every time the record is processed.

The ADEL field sets the deadband for archive monitors (DBE_LOG events), while the MDEL field controls value monitors (DBE_VALUE events).

The remaining fields are used by the record at run-time to implement the record monitoring functionality.

Field	Summary	Type	DCT	Default	Read	Write	CA PP
ADEL	Archive Deadband	DOUBLE	Yes	 	Yes	Yes	No
MDEL	Monitor Deadband	DOUBLE	Yes	 	Yes	Yes	No
ALST	Last Value Archived	DOUBLE	No	 	Yes	No	No
MLST	Last Val Monitored	DOUBLE	No	 	Yes	No	No
ORAW	Previous Raw Value	LONG	No	 	Yes	No	No 

------------------------------------------

As described above if you set AI record's MDEL to -1 it will update via camonitor each time the record is processed.
Be aware that STRINGIN has a different implementation, so check the Component Reference Manual [1] for the records that you plan to use.


Hope this helps,

Žiga


[1] for EPICS base 7.0.8 https://epics.anl.gov/base/R7-0/8-docs/ComponentReference.html

> -----Original Message-----
> From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of Neidherr,
> Dennis Dr. via Tech-talk
> Sent: Tuesday, February 11, 2025 13:51
> To: tech-talk at aps.anl.gov
> Subject: Update behavior of camonitor
> 
> Dear all,
> 
> I have a small and very basic question about the behavior of camonitor:
> It seems to be that it depends on the type of the record if I get an update in
> camonitor or not when I overwrite the record value with exactly the same
> value. Simple types like "stringout" do not trigger an update whereas a
> waveform for example does. Is there a purpose behind that difference? And
> can I somehow reproduce the "waveform-behavior" also for simple record
> types? An alternative would be to use the waveform record for everything,
> but maybe there is an easier solution.
> 
> Thanks a lot
> Greetings Dennis