Modular Mechanical Design; Figure 2: Principle Of Operation - Teledyne 700 IR Series Instruction Manual

Infrared gas detector for combustible and co2 gases

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Table Of Contents

Table of Contents

When present, the target gas absorbs a fraction of the IR radiation and the signal output from the

active detector decreases accordingly. The signal output of the reference detector remains

unchanged in the presence of the target gas. The ratio of the active/reference signal outputs is

then used to compute the target gas concentration. By using the ratio of the active/reference

signal outputs, measurement drift caused by the changes in the intensity of the IR lamp source or

changes in the optical path's reflectivity is prevented.

1.1.3

Performance Characteristics

The IR sensor maintains strong sensitivity to most all combustible hydrocarbon gases in the Lower

Explosive Limit (LEL) range. When compared with the typical catalytic bead LEL sensor, the IR

sensor exhibits improved long-term zero and span stability. Typical zero calibration intervals

would be quarterly to semi-annual and typical span intervals would be semi-annual to annual.

However, actual field experience is always the best determination of appropriate calibration

intervals.

NOTE: The OLCT 700/710 IR detector will not respond to combustible gases that are not

hydrocarbons, such as H

gases.

The IR sensor generates different signal sensitivity levels for different combustible hydrocarbon

target gases. Unless otherwise specified the OLCT 700/710 IR detector will be factory calibrated

for methane service. If the target hydrocarbon gas is other than methane, then the unit will have

to be span calibrated and configured accordingly per this Instruction Manual.

1.2