Discriminating HiHi, Hi, Lo, LoLo alarms

[Aaron Teitlebaum]

For the custom alarm type, you can specify HiHi, Hi, Lo, and LoLo limits that will trigger the alarm. Is there any way to tell which of the four limits has been exceeded when the alarm is triggered, other than manually comparing the PV value to each of the limits? The documentation says:

Quote

• High – indicates the High limit value. When the Tag value is equal to or greater than the Hi Limit value,  the Hi limit alarm is generated. 

• HiHi  -  indicates the High High limit value. When the Tag value is equal to or greater than the HiHi Limit  (Tag value is too high ) the HiHi limit alarm is generated. 

• Low - indicates the low limit value. When the Tag value is lower than or equal than the low Limit  (Tag ) the low limit alarm is generated

• LoLo -  indicates the low low limit value. When the Tag value is lower than or equal than the LoLo Limit  (Tag ) the LoLo limit alarm is generated.

This seems to imply that these are four separate alarms (Hi, HiHi, Lo, and LoLo), but as far as I can tell, exceeding any of the limits will all generate the same one alarm. If that's the case, what's the point of being able to specify a HiHi or LoLo alarm limit when this alarm will already have been triggered when the Hi or Lo limit is exceeded?

[Dave]

In the alarm summary, the particular trigger that initiated the alarm is shown in the "Change" column.

Myself, I don't find this particularly useful and would be inclined to create 4 separate alarms...two configured as warnings(Lo & Hi) with a lower severity/priority, and two with a higher severity/priority (HiHi & LoLo). This way you can have the alarm banner colour display change depending on the warning/alarm. To enable this, set the Banner Color Mode to "by highest severity". The colors can be defined in the "Severity Colors" collection. The alarm display name can also be unique to each alarm when configured this way.