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Model 20X Series
Gas Sensor Monitors
Model 201 - Combustible Gas
Model 203 - Hydrogen Sulfide
Model 206 - Carbon Monoxide
Sierra Monitor Corporation 1991 Tarob Court Milpitas, California 95035 (408) 262-6611 (800) 727-4377 Fax: (408) 262-9042
The Model 20X Series are all-weather,
solid-state, fixed-installation single-
alarm monitors designed for continuous
area monitoring of Combustible Gas,
Hydrogen Sulfide or Carbon Monoxide.
The Model 20X Series consists of 3 gas sensor mod-
ules, Model 201 for Combustible Gas, Model 203 for
Hydrogen Sulfide and Model 206 for Carbon Monoxide.
The monitors provide 0.5 Amp dry contract relay that is
activated when the concentration of gas exceeds the
factory-set (and user-adjustable) level. A TTL signal can
be user configurable to interface with Sierra Monitor's
alarm panels. This signal may be used to activate a
remote alarm, fan or process controller.
The standard configuration has a normally operating open
relay but a fail-safe normally operating closed relay is
field selectable. A durable, cast aluminum explosion-
proof enclosure houses the sensor electronics. The en-
closure provides sealing for hazardous areas - Class I,
Division 1, Groups C, D. The sensor with porous metal
cover is assembled in an aluminum housing that screws
directly into the electronics enclosure. The cover both
protects the sensor and acts as a flame-arrestor. The
monitor can be installed up to 500 feet from the power
source.
Semiconductor-Type Sensor
A solid-state semiconductor-type sensor and associated
electronic circuitry ensure trouble-free, long-term opera-
tion. There are no pumps, filters, or chemical cells to
replace or maintain. Except periodic calibration to verify
the alarm setting, no attention is required after installa-
tion. The user may adjust the alarm level by using cali-
bration gas with concentration equal to the alarm level.
Remote Alarm Available
If a remote alarm is desired (required for 20X-00), the
Model 2102 Dual Channel Alarm Panel can be connected
up to 500 feet away from the monitors.
Model 201 - Combustible Gas
The Model 201 can detect a wide range of combustibles.
Typical applications include combustible gas monitor-
ing in manholes, tanks, natural gas fields, parking ga-
rages and vehicle maintenance facilities, sewage treat-
ment plants, laboratories, chemical plants, and more.
Features Benefits
Explosion-proof enclosure Can operate continuously in work areas where
hazardous gases could be present
No chemical cells to replace, no periodic Maintenance free operation
maintenance required other than routine
calibration
All the electronic circuitry needed to operate Quick easy installation and connection to alarm
panel the monitor contained in a compact unit