Detcon 1000_CO2 - Manual (Page 8)

Model 1000 CO2
Model 1000 CO2 Instruction Manual Rev. 2.2 Page 4 of 28
Figure 5 IR Block Diagram
1.1.5 Characteristics
The NDIR optical sensor element maintains strong sensitivity to CO
2
. Typical zero calibration intervals would
be quarterly and typical span calibration intervals would be quarterly to bi-annual. However, actual field
experience is always the best determination of appropriate calibration intervals.
Figure 6 Principal of Operation
The NDIR optical sensor readings can be adversely affected by dust, dirt and oil mist accumulation as well as
severe corrosion. These deposits may reduce the optical reflectivity inside the sensor, and although accurate
readings are continually maintained, excessive loss in useable signal eventually gives way to noise and
unstable readings. The optical sensor may, over a period of time (3-7 years), lose its IR lamp source filament,
and in this case, an optical sensor modular replacement is required. The IR-640/IR-642 has an extensive list of
Fault Diagnostics to alert and pinpoint operational problems. See Troubleshooting, section 12.0.
Figure 7 IR Response Curve
1.2 Explosion Proof Enclosures
The sensors are packaged in cast metal explosion proof enclosures. The enclosures are fitted with a threaded
cover with glass lens window. Magnetic program switches located behind the transmitter module faceplate are
activated through the lens window via a hand-held magnetic programming tool allowing non-intrusive
operator interface with the sensor. All calibration and alarm level adjustments can be accomplished without
removing the cover or declassifying the area. Electrical classification is Class I; Groups B, C, D; Div. 1.