Detcon IR-622 - Manual (Page 6)

tained, excessive loss in useable signal eventually gives way to noise and unstable readings. The optical sensor may, over long
periods of time (3-7 years), lose its IR lamp source filament, and in this case an optical sensor modular replacement is
required. The IR-622 has an extensive list of Fault Diagnostics to alert and pin-point operational problems. See section 3.10
3.2 A
PPLICATION
Model IR-622 MicroSafe™ sensors are designed to detect and monitor combustible hydrocarbon gas in ambient air in
the range of 0-100% LEL. Minimum sensitivity and scale resolution is 1%. Operating temperature range is -40° F. to
+175° F. While the sensor is capable of operating outside these temperatures, performance specifications are verified
within the limit.
3.2.1 Sensor Placement/Mounting
Sensor location should be reviewed by facility engineering and safety personnel. Area leak sources and perimeter mounting
are typically used to determine number and location of sensors. The sensors are generally located 2 - 4 feet above grade.
3.2.2 Response to Different Gases
The MicroSafe™ IR-622 responds to all combustible hydrocarbon gases, but at different signal strengths. In order to maintain
accurate readings, the detector must be calibrated to the specific target gas of interest.
The MicroSafe™ IR-622 is factory calibrated for the specific target gas chosen at the time of order. Unless otherwise speci-
fied by the customer, the detector will be factory calibrated for methane service. Once installed in the field, if a combustible
hydrocarbon gas other than the gas specified at the time of order is being measured, contact Detcon for the appropriate field-
replaceable electronics/software upgrade. The calibration gas used to span the IR-622 must be the same gas type as the target
gas being measured.
3.3 S
PECIFICATIONS
Method of Detection
NDIR Optical
Electrical Classification
Class I; Groups B, C, D; Div. 1.
Response Time
T50 < 15 seconds; T90 < 35 seconds
Detcon Model IR-622 Combustible Hydrocarbon Sensor PG.6
Functional
Block
Diagram
Functional
Block
Diagram
Analog 4-20 mA Out
Power In
Relays Out
Pre-Amp Display
Temperature
Compensation
Alarm & Fault
Relays
RS-485 & 4-20mA
Micro-
processor
Transmitter
Power Supply
Optical
Sensor
I/O Circuit
Protection
Serial RS-485 Out
0
4
8
12
16
20
20 40 60 80 100
% LEL (lower explosive limit)
m
A
D
C
S
ig
n
a
l
O
u
tp
u
t
Output Response Curve