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Rev. 2.1 7-7-2017
Copyright © 2017 by Cool Air Incorporated. All rights reserved.
Relay Status LEDs
Each relay has a surface-mounted LED associated with it that
indicates the status of the relay. A relay is energized (a non-alarm
condition) when its LED is lighted (green), and de-energized (an
alarm condition) when the LED is not lighted.
External Connections
Contacts for external connections:
4–20 mA outputs for ammonia level
Auxiliary Relay contacts
Alarm Relay contacts
Pre-alarm Relay contacts
LBW-420-LEL DC Power
4–20 mA Analog Outputs
The detector has a 4-20 mA analog output that allows it to
communicate with external devices such as computers, PLCs, and
digital displays. The output conforms to ISA S50.01 ratings, Type
2L and Type 2H (two-wire).
The ammonia level detector output current
(TB2, “Sensor 4-
20mA” terminals on lower left of Enclosure Mounted Circuit
Board) is proportional to ammonia PPM with the proportionality
constant dependent on the range. The PPM value can be determined
using one of the following formulae:
% NH3 = .041667 (I – 4)
0 to 1% Range
% NH3 = .083334 (I – 4)
0 to 2%Range
% NH3 =.4166667(I – 4)
0 to 10% Range
Where % NH3 equals ammonia concentration in percent and I equal
the output current in mA. For example, if the current is 4 mA, then
the ammonia concentration is 0 %. If the current is 20 mA, then the
ammonia concentration is 1% PPM (1% range), 2% (2% range), and
10% (10% range)
