Description of alarm actions, 2 direction of alarm action, 3 hysteresis – Yokogawa JUXTA VJA7 User Manual
Page 4: 4 alarm on delay and alarm off delay, 5 direction of relay action
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All Rights Reserved. Copyright © 1999, Yokogawa M&C Corporation
IM 77J01A07-01E
8.3.2
Direction of Alarm Action
Select the direction of alarm-1 action and that of alarm-2 action
from among HIGH ALM (high-limit alarm) and LOW ALM (low-
limit alarm) and set each in E05: ALM1 ACTION (direction of
alarm-1 action) or E06: ALM2 ACTION (direction of alarm-2 ac-
tion).
● To activate alarm status when input signal
Ն alarm setpoint,
select HIGH ALM.
● To activate alarm status when input signal
Յ alarm setpoint,
select LOW ALM.
8.3.3
Hysteresis
Set alarm-1 and alarm-2 hysteresis, in E09: HYSTERESIS1 and
E10: HYSTERESIS2. Hysteresis is a value added to the alarm
setpoint in order for an alarm status to be released (to normal) after
the alarm status has been activated. The alarm status will be re-
leased in the following conditions, depending on the direction of
alarm action.
*
When HIGH ALM (high-limit alarm) is set: Alarm is released
when input signal < (alarm setpoint - hysteresis).
*
When LOW ALM (low-limit alarm) is set: Alarm is released
when input signal > (alarm setpoint + hysteresis).
● Setting range: A range of 0 to 100% of input range
● Setting resolution: 0.1%
8.3.4
Alarm ON Delay and Alarm OFF Delay
Set alarm-1 and alarm-2 ON delays in E11: ON DELAY1 and
E12: ON DELAY2 and then alarm-1 and alarm-2 OFF delays in
E13: OFF DELAY1 and E14: OFF DELAY2.
An alarm ON delay is a delay time from the establishment of
alarm condition to alarm output; an alarm OFF delay is a delay
time from the establishment of return-to-normal condition to out-
put.
● Setting range: 0 to 999 seconds
● Setting resolution: 1 second (Note that about 0.2 second will
be added to set time to prevent erroneous operation.)
For example, when an alarm ON delay is set to 1 second, alarm
output is generated if alarm status continues for more than 1 sec-
ond after the input value exceeds the alarm setpoint. Further, when
an alarm OFF delay is set to 2 seconds, alarm output is released if
normal condition continues for more than 2 seconds after the input
value has returned to normal from the alarm status.
8.3.5
Direction of Relay Action
Set the direction of relay energizing in alarm-1 normal condition
and alarm-2 normal condition by selecting from among NRM DE-
ENERGIZED (de-energized under normal condition) and NRM
ENERGIZED (energized under normal condition) in E15: RL1
ACTION and E16: RL2 ACTION and set them.
9. DESCRIPTION OF ALARM ACTIONS
This chapter describes examples of alarm actions under the following conditions.
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[1]
[2]
[3]
[4]
1 sec.
2 sec.
3 sec.
4 sec.
Alarm-2 hysteresis (5%)
Alarm-1 hysteresis (10%)
Alarm-1 setpoint (80%)
Alarm-2 setpoint (15%)
Elapsed time
1 sec.
Alar
m conditions estab
lished
Alar
m-1 ON dela
y
Alar
m-1 OFF dela
y
Alar
m conditions
estab
lished
Alar
m conditions
estab
lished
Nor
mal conditions
estab
lished
Nor
mal conditions
estab
lished
Lo
w-limit alar
m ON
Lo
w-limit alar
m OFF
Alar
m-2 ON dela
y
Alar
m-2 OFF dela
y
Alar
m conditions estab
lished
High-limit alar
m ON
High-limit alar
m OFF
Nor
mal conditions estab
lished
Nor
mal conditions estab
lished
[1]: Alarm status does not continue for more than 1 second after the
alarm conditions are established at alarm-1.
[2]: Normal status does not continue for more than 2 seconds after the
normal conditions are established at alarm-1.
[3]: Alarm status does not continue for more than 3 seconds after the
alarm conditions are established at alarm-2.
[4]: Normal status does not continue for more than 4 seconds after the
normal conditions are established at alarm-2.
Alarm-1 action
Alarm-2 action
Alarm
Normal
Normal
Normal
Alarm
Normal