Setting Alarms; Alarm Values; Alarm Output Actions - YOKOGAWA ZR402G User Manual

8.3

Setting Alarms

The analyzer enables the setting of four alarms high-high, high, low, and low-low alarms
depending upon the oxygen concentration. The following section sets forth the alarm operations
and setting procedures.
8.3.1

Alarm Values

(1) High-high and high alarm values
High-high alarms and high alarms are issued when they are set to be detected with
parameter codes "D41" and "D42", and if the measured values exceed the preset oxygen
concentration values specified with "D01" and "D02".
(2) Low and low-low alarm values
Low alarms and low-low alarms are issued when they are set to be detected with parameter
codes "D43" and "D44", and if the measured values are lower than the preset oxygen
concentration values specified with "D03" and "D04".
8.3.2

Alarm Output Actions

If the measured values of the oxygen concentration fluctuate between normal (steady-state)
values and alarm setting, there may be a lot of alarm-output issuing and canceling. To avoid this,
set the delay time and allow for hysteresis for alarm canceling under the alarm output conditions,
as Figure 8.2 shows. When the delay time is set, an alarm will not be issued so quickly even
if the measured value differs from the steady-state and enters the alarm setpoint range. If the
measured value remains within the alarm setpoint range for a certain period of time (for the
preset delay time), an alarm will result. On the other hand, there will be a similar delay each
time the measured value returns to the steady state from the alarm setpoint range (canceling
the alarm status). If hysteresis is set, alarms will be canceled when the measured value is less
than or more than the preset hysteresis values. If both the delay time and hysteresis are set, an
alarm will be issued if the measured value is in the alarm setpoint range and the delay time has
elapsed. When the alarm is reset (canceled), it is required that the measured value be beyond
the preset hysteresis value and that the preset delay time. Refer to Figure 8.2 for any further
alarm output actions. The delay time and hysteresis settings are common to all alarm points.
7.5%
High alarm setpoint
5.5%
Oxygen concentration
Alarm output ON
OFF
Figure 8.2
In the example in Figure 8.2, the high alarm point is set to 7.5% O
seconds, and hysteresis is set to 2% O
Alarm output actions in this figure are expressed as follows:
(1) Although oxygen concentration measurement "A" has exceeded the high alarm setpoint,
"A" falls lower than the high alarm setpoint before the preset delayed time of five seconds
elapses. So, no alarm is issued.
(2) Oxygen concentration measurement "B" exceeds the high alarm setpoint and the delayed
time has elapsed during that measurement. So, an alarm results.
A
Delayed time:
Delayed time:
5 seconds 5 seconds
Alarm Output Action
2
<8. Detailed Data Setting>
Alarm range
B
.
C
D
Delayed time:
5 seconds
F8.2E.ai
, the delayed time is set to five
2
IM 11M12A01-04E 11th Edition : Jul. 19, 2017-00
8-8
Hysteresis
2.0%