Yokogawa JUXTA VJTK - Manual (Page 4)

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All Rights Reserved. Copyright © 1999, Yokogawa M&C Corporation IM 77J01T21-01E 2nd Edition : 2007.02.09-00
9.2.3 Hysteresis
Set the alarm-1 and alarm-2 hysteresis in E07: HYSTER-
ESIS1 and E08: 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 acti-
vated. The alarm status will be released in the following con-
ditions, depending on the direction of alarm action.
*
When HIGH ALM (high-limit alarm) is set: Alarm is re-
leased when input signal < (alarm setpoint - hysteresis).
* When LOW ALM (low-limit alarm) is set: Alarm is re-
leased when input signal > (alarm setpoint + hysteresis).
● Setting range: 0 to 100% of input range
● Setting resolution: 0.1 ° C
9.2.4 Alarm ON Delay and Alarm OFF Delay
Set the 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 the condition monitoring time from the
establishment of alarm conditions to its output; an alarm OFF
delay is the condition monitoring time from the establishment
of return-to-normal conditions to its output.
10. DESCRIPTION OF ALARM ACTIONS
This chapter describes examples of alarm actions under the following conditions.
Item
Alarm 1 Alarm 2
Parameter Setpoint Parameter Setpoint
Direction of alarm action E05 : ALM1 ACTION High-limit alarm E06 : ALM2 ACTION Low-limit alarm
Alarm setting E01 : SET POINT1 80% E02 : SET POINT2 15%
Hysteresis E07 : HYSTERESIS1 10% E08 : HYSTERESIS2 5%
Alarm ON delay E11 : ON DELAY1 1 sec E12 : ON DELAY2 3 sec
Alarm OFF delay E13 : OFF DELAY1 2 sec E14 : OFF DELAY2 4 sec
Description of
alarm actions
The alarm is output if the condition where
the input value is 80% or more of high-
limit alarm continues for 1 second or
more.
After the alarm is output, when the
condition where the input value is less
than 70% of high-limit alarm continues for
2 seconds or more, the status returns to
normal. The alarm is output if the condition where
the input value is 15% or less of low-limit
alarm continues for 3 seconds or more.
After the alarm is output, when the
condition where the input value is more
than 20% of low-limit alarm continues for
4 seconds or more, the status returns to
normal.
[%]
0
20
15
40
60
80
100
[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
Alarm-1 ON delay Alarm-1 OFF delay
Alarm conditions established Alarm conditions established Normal conditions established Normal conditions established
Low-limit alarm ON Low-limit alarm OFF Alarm-2 ON delay Alarm-2 OFF delay
[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 conditions established Alarm conditions established
High-limit alarm ON High-limit alarm OFF
Normal conditions established Normal conditions established
Alarm-1 action
Alarm-2 action
Alarm Normal Normal
Normal Alarm Normal
● Setting range: 0 to 999 seconds
● Setting resolution: 1 second (However, about 0.2 second
is to be added to set time to prevent wrong operation.)
For example, when an alarm ON delay is set to 1 second,
alarm output is generated if alarm status continues for 1 sec-
ond or more after the input value exceeds the alarm
setpoint. Further, when an alarm OFF delay is set to 2 sec-
onds, alarm output is released if normal condition continues
for 2 seconds or more after the input value has returned to
normal from the alarm status.
9.2.5 Direction of Relay Action
Select the direction of relay energizing in alarm-1 normal
condition and alarm-2 normal condition 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.