Detcon FP-524HT - Manual (Page 3)

3.0 D ESCRIPTION
Detcon MicroSafe™ Model FP-524HT, combustible gas sensors are non-intrusive “Smart” sensors designed to
detect and monitor combustible gas in air over the range of 0-100% lower explosive limit (LEL), and this model
uses a sensor head that is specially rated to operate up to 150°C. One of the primary features of the sensor is its
method of automatic calibration which guides the user through each step via instructions displayed on the backlit
LCD. The sensor output is a standard 4-20 mA signal. The microprocessor supervised electronics are packaged as a
plug-in module that mates to a standard connector board. Both are housed in an explosion proof condulet that
includes a glass lens. A 16 character alpha/numeric indicator is used to display sensor readings as well as the sen-
sor’s menu driven features via a hand-held programming magnet.
The sensor technology is of the catalytic pellistor type. Catalytic pellistors show a good response to a long list
of combustible gases. Refer to section 3.7.1 for a partial list of detectable gases. The technique is referred to as non-
selective and may be used for the detection and monitoring of target combustible gases. Model FP-524HT sensors
are specif ically designed to be resistive to poisons such as sulf ides, chlorides and silicone. The sensors are character-
istically stable and capable of providing reliable performance for periods exceeding 5 years in most industrial envi-
ronments.
3.0.1 Catalytic Detector
The FP524HT’s catalytic detector is supplied as a matched pair of elements mounted in a special 150°C rated thread-in
replaceable housing. One element is an active catalytic detector and the other is a non-active compensating element.
Each element consists of a fine platinum wire embedded in a porous bead. A catalytic mixture is applied to the detect-
ing element while the compensating element is treated so that catalytic oxidation of gas does not occur. The beads are
mounted in a plug-in module that is enclosed by a sintered porous stainless steel f lame arrestor. The plug-in sensor
features gold plated pins and mounts inside a stainless steel sensor housing via a mating gold plated socket.
Model FP-524HT Combustible Gas Sensor PG.3
Alumina Bead
Platinum Wire
Catalyst
Construction of
Detector Bead
Sintered Stainless Steel Can
Header
Gold Plated Pins
Beads