Alarms; 1Alarm Display - ABB AW400 Series Instruction Manual

4.4.3 Alarms

This menu allows to set high and low alarm levels and the dead band. The alarm levels are freely selectable
by the user. Select the channel and press Enter to select alarms and dead band. Default levels are
automatically related to the set range of output: low alarm is set at 10 % of Out Zero and high alarm is set at
90 % of Out Max (see the following table for default alarm setting values).
Parameter Unit
pH pH
mV mV
O3 ppm
Cl ppm
CD ppm
T °C
mA mA
Dead band is useful to avoid a repeated switch on and off of an alarm condition. The operation principle is
represented in figure 12 below: if the measured value reaches the high alarm level, AW400 generates an
alarm message, but a second alarm condition is triggered only after the measure lowers below the set dead
band, and then rises again above the HI alarm level. A similar procedure of opposite sign is performed for low
alarm.
To identify contacts for alarm retransmission, see the operation description for each instrument type in the
following chapters.
Dead Dead
Band Band
Alarm
OFF
LoAl
ON
Low Alarm High Alarm
Fig. 12 - HI and LO alarm dead-band

4.4.3.1Alarm Display

When an alarm occurs, the display indication will flash on and off to signal the alarm condition.
By pressing the ENTER key, the alarm page will be called on display, and it will be possible to identify the
channel and the alarm type .
See Par. 9.1.3 for details.
low high
3.00 11.00
-450 +450
0.10 0.90
0.10 0.90
0.10 0.90
10.0 90.0
6.40 17.60
HiAl
ON
Measured value
Alarm
dead band
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Dead Dead
Band Band
Alarm
LoAl OFF
ON
Low Alarm High Alarm
HiAl
ON
Measured value
33