Experimental Physics and
Industrial Control System

> $ALARMCOUNTFILTER 3 8

> I see the following behaviour in alh:
>
>    6 seconds after the alarm starts toggling, the PV goes into alarm.
>    After another 6 seconds, the PV goes out of alarm.

The behaviour is as intended, if the PV changes once per second its state.
Because you've specified the filter "3 8":
it goes in the alarm state, if the alarm either stays for 8 seconds,
or if it enters an alarm state three times within 8 seconds.

This PV enters an alarm state every two seconds, so after six seconds it raised an alarm the third time.

If you would change the filter to for example 
 
$ALARMCOUNTFILTER 5 8

then it would never go into alarm (if the PV sticks to its behaviour).
When it would stop toggling and stays instead into alarm, an alarm would be raised after 8 seconds.
If it would change its state more frequent, an alarm would be raised as well.

I hope that helps to clarify the ALARMCOUNTFILTER.

Cheers from Switzerland :-)
Andreas