CD Automation srl
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14.3.1
Alarm Function
General notes:
An automatic regulation, control and / or supervision takes into consideration different alarms.
In general, the alarms are "digital" elements or rather elements that can take only two values (true or false)
because rhe condition that describes the alarm can only be 'true' (ON) or "false" (OFF).
The condition that describes the alarm is usually summarized by the ALARM FUNCTION because it defines
its behavior.
Over the years, depending on the specific needs of various systems have been developed many different
types of alarm
(for example alarms, trends, alarms group, put alarms, etc. ....).
Here we will only considering alarms normally implemented on this controller.
The Functions of the alarms in the controller are 3 as follows:
1) Process alarm (or absolute)
2) Band Alarm
3) Deviation Alarm
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1)
Process alarm (or absolute)
The process alarm can be of
two types:
A) Up alarm
B) Low alarm
Generally, the process alarm is an alarm which compares the instantaneous value of the measure (
M
) with
the value assigned to the alarm (
SA)
(Threshold value)
A)
If it is an
Up alarm
, the alarm will be ON when the measured value exceeds the threshold value
B)
If it is a
Low alarm
, the alarm will be ON when the measured value is less than the threshold value
(M < AS).
