23
Fig. 4.5 Rate Alarms
100
50
12 3 4
t (191 secs)
Hours
% Engineering Range
Alarm Off
Alarm On
t (191 secs)
5
…4.3.2 Alarms – Figs. 4.3, 4.4, 4.5 and 4.6
t = 10.81 +
t = 191 seconds
1800
4 CONFIGURATION MODE…
trip value (as a % of eng. span/hr)
Information
Fast/Slow Rate Alarms – an alarm becomes active when the rate of
change in the process variable is faster or slower than the configured
alarm value. Rate of change alarm values are configured as a % of span
change per hour. The elapsed time period before the alarm condition is
detected is dependant upon the configured alarm value. This period can
be calculated as follows:
The alarm remains active until the rate of change in the process variable
returns to the non-alarm condition. The calculated time period (t)
elapses between the process variable reaching the non-alarm condition
and the alarm becoming inactive.
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