Instruction Manual

3.0.2 Microprocessor Control Circuit
The control circuit is microprocessor based and is packaged as a plug-in field replaceable module, facilitating easy
replacement and minimum down time. Circuit functions include a basic sensor pre-amplifier, sensor temperature
measurement, on-board power supplies, microprocessor, back lit alpha numeric display, alarm status LED indica-
tors, magnetic programming switches, an RS-485 communication port, and a linear 4-20 mA DC output.
3.0.3 Base Connector Board
The base connector board is mounted in the explosion proof enclosure and includes: the mating connector for the
control circuit, reverse input and secondary transient suppression, input filter, alarm relays, lugless terminals for all
field wiring, and a terminal strip for storing unused programming jumper tabs. The alarm relays are contact rated 5
amps @ 250 VAC, 5 amps @ 30 VDC and coil rated at 24 VDC. Gold plated program jumpers are used to select
either the normally open or normally closed relay contacts.
3.0.4 Explosion Proof Enclosure
Detcon Model IR-622 Combustible Hydrocarbon Sensor PG.4
NC
ALARM 1
WHT
BLK YEL
BLU
MA
VDC Power In
Optional RS-485
Terminating Resistor
Use 120 ohm
NO
NC
NO
NC
NO
NO/NC
COM
NO/NC
COM
NO/NC
COM
FAULT ALM-2 ALM-1
Alarm Dry Contacts
ALARM 2
FAULT
R1
R2
A
B
A
B
4-20 mA Output
RS-485 In
RS-485 Out
Optional 4-20 mA
Signal Developing Resistor
Use 250 ohm 1/4w
JU
M
P
E
R
S
U
N
-U
S
E
D
RED BRN
Jumper Programmable Alarm Outputs
Normally Open or Normally Closed
Sensor
Place un-used alarm programming
jumper tabs here
detcon inc.
Program Switch #2
FLT
ALM
1
CAL
MicroSafe™ LEL Gas Sensor
HO USTON , TEXA S
PGM 2
PGM 1
ALM
2
MODEL IR-622
CONTRAST
Alarm & Cal LEDs
Program Switch #1
Menu Driven Display
Plug-in Microprocessor Control Circuit
Display Contrast Adjust
Porous Membrane
Optical Filter
Active Detector
Lamp
Reference Detector
Optical Sample Gas Chamber
H
C
H
H
H
H
C
H
H
H
Optical Filter