Detcon TP-424C - Manual (Page 3)

3.0 D ESCRIPTION
Detcon Model TP-424C, hydrogen sulfide sensors are designed to detect and monitor H2S in air over the
range of 0-100 ppm. The sensor assembly consists of a solid state semi-conductor sensor in a stainless steel
housing, a plug-in control transmitter circuit, a base connector board and an explosion proof enclosure. The
sensor assembly is suitable for use in Class I; Div. 1; Groups B, C, D electrically classified areas.
Sensor Technology
The sensor technology is a patented solid state metal oxide semiconductor. The sensor consists of two thin
f ilms; a temperature sensitive heater f ilm, and an hydrogen sulf ide sensitive sensor f ilm. Both f ilms are
deposited on a silicon microchip by vacuum deposition. The heater f ilm elevates the operating temperature
of the sensor f ilm to a level where a good sensitivity and response to hydrogen sulf ide is achieved. The sensor
f ilm is a proprietary metal oxide that shows a dynamic response to hydrogen sulf ide gas. Range of sensitivity
is from part per billion to % by volume. The rugged sensor is capable of maintaining its operating character-
istics for periods of up to 7-10 years in most industrial environments and as such, is supported by a 10-year
conditional warranty.
Plug in Control Transmitter Circuit
The control transmitter is a remote mounted electronic circuit designed and packaged as a plug-in module.
The transmitter assembly consists of several circuit functions: input power conditioning, sensor heater con-
trol, sensor signal conditioning, sensor fault supervision, and fault LEDs. A metallic face plate with pull
ring identifies test points and calibration adjustments. The plug-in module design supports easy field level
maintenance and repair. The mating plug is gold plated for maximum resistance to corrosion.
Detcon Model TP-424C Hydrogen Sulfide Sensor PG.3
Construction of
Semiconductor Sensor
Sensor
Film
Heater
Film
Silicon
Microchip