Alarms; Generic Alarms - gefran 3850T Use And Installation Manual

7. EXAMPLES AND APPLICATION NOTES
7.4.

Alarms

7.4.1.

Generic alarms

Generic alarms AL1 ... AL4 can be predominantly of 4
types, shown below:
Normal type absolute alarm
AL1 inverse and absolute, AL2 direct and absolute.
Two alarm thresholds are set, AL1 (lower threshold) and
AL2 (upper threshold), which correspond to two hysteresis
values Hyst1 (positive) and Hyst2 (negative). The alarm is
triggered when the measured value remains below AL1 or
greater than AL2 for the set activation delay times (delay).
The alarm condition stops when the measured value is
greater than AL1 + Hyst 1, or is less than AL2 - Hyst2. This
avoids repeated alarms caused by slight variations in the
measured value.
Any alarm signal on power-up, when the equipment is not
running, can be avoided by disabling it when power is
turned on.
Note: in the event of a direct alarm, hysteresis creates a
band lower than the reference value, while in the case of an
inverse alarm, it creates it higher than this value.
Symmetric type absolute alarm
A single AL1 alarm threshold and a single Hyst1 hysteresis
value are set.
With the direct alarm setting, the alarm is triggered when
the measured value is less than AL1 - Hyst1 or greater than
AL1 + Hyst1 for the set delay activation time (delay)
With the inverse alarm setting, the alarm is triggered when
the measured value is greater than AL1 - Hyst1 or less than
AL1 + Hyst1 for the set delay activation time (delay).
Normal type setpoint alarm
A single alarm limit AL1 and Hyst1 hysteresis value (nega-
tive) are set.
With the direct alarm setting, the alarm is triggered when
the measured value is greater than SP + AL1 for the set de-
lay activation time (delay). The alarm condition stops when
the measured value is less than SP + AL1 - Hyst1.
With the inverse alarm setting, the alarm is triggered when
the measured value is less than SP + AL1 - Hyst1 for the
set delay activation time (delay). The alarm condition stops
when the measured value exceeds SP + AL1.
The setpoint alarm allows you to implement dynamic
thresholds that automatically follow the setpoint time trend.
Symmetric type setpoint alarm
A single AL1 alarm threshold and a single HYST1 hysteresis
value are set.
With the direct alarm setting, the alarm is triggered when
the measured value is less than SP-AL1 or higher than SP
+ AL1.
With the inverse alarm setting, the alarm is triggered when
the measured value is between SP - AL1 and SP + AL2.
108
Normal type absolute alarm
AL2
AL1
alarm 1
alarm 1
Symmetric type absolute alarm
AL1
reverse
direct
Normal type setpoint alarm
SP+AL1
SP
reverse
direct
Symmetric type setpoint alarm
SP+AL1
SP
SP -AL1
reverse
direct
80703B_MHW_2850T/3850T_02-2019_ENG
AL2 - Hyst2
AL1 + Hyst1
time
AL1 + Hyst1
AL1 - Hyst1
time
Hyst1
time
Hyst1
Hyst1
time