Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 95)

IM 11M13A01-04E 8-7
8. Detailed Data Setting
8.4 Setting Oxygen Concentration 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.
8.4.1 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.
The oxygen alarm set values can range from 0 to 100% O 2 .
(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.
The oxygen alarm set values can range from 0 to 100% O 2 .
8.4.2 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.
Delayed time:
5 seconds
7.5%
High-limit alarm setpoint
5.5%
Oxygen concentration
Alarm output ON
OFF
Hysteresis
2.0%
A B C D
Alarm range
Delayed time:
5 seconds Delayed time:
5 seconds
F8.2E.EPS
Figure 8.2 Alarm Output Action