
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
TheModel20XSeriesareall-weather,
solid-state, fixed-installation single-
alarmmonitorsdesignedforcontinuous
area monitoring of Combustible Gas,
HydrogenSulfide orCarbonMonoxide.
The Model 20X Series consists of 3 gas sensor mod-
ules, Model 201 for Combustible Gas, Model 203 for
HydrogenSulfideandModel206forCarbonMonoxide.
The monitors provide 0.5Amp dry contract relay that is
activated when the concentration of gas exceeds the
factory-set(anduser-adjustable)level.ATTLsignalcan
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.
Thestandardconfigurationhasanormallyoperatingopen
relay but a fail-safe normally operating closed relay is
field selectable. A durable, cast aluminum explosion-
proofenclosurehouses the sensor electronics. The en-
closure provides sealing for hazardous areas - Class I,
Division1, Groups C, D. The sensor withporous metal
coverisassembled in analuminumhousingthatscrews
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
Asolid-state semiconductor-typesensorand associated
electroniccircuitry ensure trouble-free,long-termopera-
tion. There are no pumps, filters, or chemical cells to
replaceormaintain. Except periodic calibrationtoverify
the alarm setting, no attention is required after installa-
tion. The user may adjust the alarm level by using cali-
brationgaswith concentration equal to the alarm level.
Remote Alarm Available
If a remote alarm is desired (required for 20X-00), the
Model2102DualChannelAlarmPanelcanbeconnected
up to 500 feet away from the monitors.
Model 201 - Combustible Gas
TheModel 201candetect awiderangeofcombustibles.
Typical applications include combustible gas monitor-
ing in manholes, tanks, natural gas fields, parking ga-
ragesandvehiclemaintenancefacilities,sewagetreat-
ment plants, laboratories, chemical plants, and more.
Features Benefits
Explosion-proofenclosure Can operate continuously in work areas where
hazardousgasescouldbepresent
No chemical cells to replace, no periodic Maintenancefree operation
maintenancerequiredother 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