Alarm handling is based on limit and status checking and performed in the data servers.
More complicated expressions (using arithmetic or logical expressions) can be developed by creating derived parameters on which status or limit checking is done by the data server.
Alarm handling in SCADA systems
The alarms are logically handled centrally, i.e., the information only exists in one place and all users see the same status (e.g., the acknowledgement), and multiple alarm priority levels (in general many more than 3 such levels) are supported
Most of the SCADA products that were evaluated decompose the process in “atomic” parameters (e.g. a power supply current, its maximum value, its on/off status, etc.) to which a Tag-name is associated.
The Tag-names used to link graphical objects to devices can be edited as required. The products include a library of standard graphical symbols, many of which would however not be applicable to the type of applications encountered in the experimental physics community.