D12
EX-IR
Gas Transmitter with IR Smart Sensor
Dec 2019 ( 85-0004 Rev A)
46
A
LARMS
The transmitter features three gas level alarms -
Alarm
,
Warning
, and
Caution
, as well as a
Trouble
alarm. Gas level alarms are automatically configured when a gas sensor is installed, and are retained
between changes of the same type sensor. The alarm status is indicated on the Main Display and is used
to activate the three optional relays (see Relay Operation, Menus, and Settings on page 72). It is also
available over the serial interface.
Flammable and Toxic Gas Alarms
High alarms are required when monitoring for leaks or other unintentional accumulations of flammable
gases like methane, and toxic gases like CO2. Figure 45 illustrates the default relationship of alarms for
flammable and toxic gases. The default settings for each target gas are given in IR Sensor Versions
starting on page 5.
•
Alarm
High-high alarm
•
Warning
High alarm
•
Caution
Negative drift alarm
o
Normally set to activate on negative
drift of
–
10 %FSR (full scale range).
•
Trouble alarm occurs if reading drifts to
–
20
%FSR (cannot be disabled).
Figure 45. Flammable and Toxic Gas Alarms.
Process Low Alarms
Low alarms can be used to monitor gas levels that might decrease as the result of a leak or process
malfunction. An example of this might be when monitoring normally high levels of CO2, or when
monitoring methane above its UEL of 15%VOL
16
.
Note that the transmitter normally disables the gas
level alarms for high-range hydrocarbon and CO2
sensors. The default settings for each target gas are
given in IR Sensor Versions starting on page 5.
•
Alarm
Low-low alarm
•
Warning
Low alarm
•
Caution
Positive drift alarm
o
Can be set to activate on a positive
drift of +10 %FSR (full scale range).
•
Trouble alarm occurs if reading drifts to
–
20
%FSR (cannot be disabled).
Figure 46 Process Low Alarms
16
Extreme care must be taken in these locations, since a leak of air could produce an explosive atmosphere.
High-High Alarm
High Alarm
Low Alarm
Low-Low Alarm
Low Alarm
CO
2
High Alarm