FEC920: USER GUIDE
Page 80
September 18
DEVIATION ALARMS
Figure 72 Deviation alarm parameters
RATE-OF-CHANGE ALARMS
Figure 73 Rate-of-change alarm parameters
Note:
Operation of rate-of-change alarms may be affected if an input filter (Section 6.4.1) is applied
to the input signal.
Hysteresis: 0
Dwell: 0
Hysteresis: 0
Dwell: D
Hysteresis: yes
Dwell: 0
Hysteresis: yes
Dwell: D
Hysteresis: 0
Dwell: 0
Hysteresis: 0
Dwell: D
Hysteresis: yes
Dwell: 0
Hysteresis: yes
Dwell: D
= Alarm active
= Alarm active
Deviation low alarm definitions
Deviation high alarm definitions
Symbol
Symbol
Reference
Deviation
Hysteresis
Input signal
Hysteresis
Deviation
Reference
Input signal
Hysteresis: 0
Dwell: 0
Hysteresis: 0
Dwell: D
Hysteresis: yes
Dwell: 0
Hysteresis: yes
Dwell: D
= Alarm active
Deviation band alarm definitions
Symbol
Hysteresis
Deviation
Reference
Deviation
Hysteresis
Input signal
Rate-of-change alarm definitions
Symbol
Symbol
Rate-of-change rise active
Rate-of-change fall active
A
mo
u
n
t
‘Change Time’ units
(second, minute or hour)
Present
time
A rate-of-change alarm is active if the monitored value changes by more than one ‘Amount’ in less
than 1 ‘Change time’. Dwell delays the alarm on-time. Averaging removes the effects of signal
noise.
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