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Instruction Manual
Model 4105 Gas Sensor Module (12/02)
Page: 1
1. PRODUCT DESCRIPTION
1.1 Introduction
Model 4105 Series Gas Sensor module features non-
intrusive calibration, 4-20 mA output signal and local
continuous display of the gas concentration in ppm
(toxics), % LEL (Combustibles), or % vol (Oxygen). It
is designed for use with industry standard control in-
struments.
This manual provides instructions for 4105 series gas
sensor modules that utilize common packaging and
transmitter electronics with different sensors for de-
tection of various gases. The full model number of
the gas sensor module includes a suffix, 4105-XX,
where “XX” is a number that identifies a gas type.
1.2 Application
The Model 4105-XX Gas sensor is intended for use in
ambient monitoring applications. It is designed for
fixed installation and for continuous operation.
Optional fittings and adapters can be supplied by Si-
erra Monitor to provide continuous sample delivery
to the sensor module.
1.3 Configuration
The gas monitor is comprised of a NEMA-7/4 enclo-
sure which contains the transmitter electronics and a
gas sensor which is installed in one of the two 3/4"
conduit hubs.
1.3.1 Electronics
When installed, the transmitter electronics will be con-
nected to a power supply and control device via three
wire cable.
The electronics provide a 4-20 mA current loop which
is proportional to the full sensitivity of the sensor.
Integral features include:
- L.C.D. readout of ppm of gas concentration.
- Magnetic switches for non-intrusive calibration.
- Visual indicators for fault condition.
- Electrical fault (0 mA) to controller.
The transmitter electronics assembly includes a
printed circuit assembly and a cover plate which con-
tains the L.C.D. readout and magnetic switches for
calibration.
1.3.2 Sensor
The gas sensor cell is enclosed in a threaded housing
and is plugged into a signal card located in the enclo-
sure. This configuration allows for easy field replace-
ment of the sensor cell.
Combustible: The gas sensor is a catalytic bead type.
Toxics & Oxygen: The gas sensor is an Electro Chemi-
cal type.
Figure 1.1 Model 4105 Gas Sensor Module
Figure 1.2 Outline View - Gas Sensor Module
5.42"
2.81"
1.75"
5.50"
4.50"
7.25"
Unity SPAN ZERO
FAULT /KEYPAD
CAL
Milpitas, CA
Ph. 408-262-6611
MODEL 4105-02
Combustibles
% LEL