Detcon FP-624D - Manual (Page 5)

Model FP-624D
FP-624D Instruction Manual Rev. 1.2 Page 1 of 42
1. Introduction
1.1 Description
Detcon Model FP-624D combustible gas sensors are non-intrusive “Smart” sensors designed to detect and
monitor combustible gases in air. Range of detection is 0-100% LEL (Lower Explosive Limit). The sensor
features an LED display of current reading, fault, and calibration status. The sensor is equipped with standard
analog 4-20mA, Modbus
TM
RTU output, and 3 relay contact outputs. A primary feature of the sensor is its
method of automatic calibration, which guides the user through each step via fully scripted instructions
displayed on the LED display.
The microprocessor-supervised electronics are packaged as a plug-in replaceable Transmitter Module that is
housed in an explosion proof junction box. The Transmitter Module includes a four character alpha/numeric
LED used to display sensor readings, and the sensor’s menu driven features when the hand-held programming
magnet is used.
Figure 1 Sensor Assembly Front View
Catalytic Bead (Pellistor) Sensor Technology
The sensor technology is a poison-resistant catalytic bead type. Catalytic bead sensors show a strong response
to a long list of combustible gases. The sensor is supplied as a matched-pair of detector elements mounted in a
plug-in replaceable module. One bead is a catalytically active detector and the other is a non-active reference
detector. Each detector consists of a fine platinum wire coil embedded in aluminum oxide. A catalytic
mixture is applied to the active detector while the reference detector is treated so that oxidation of the gas does
not occur. The technique is referred to as non-selective and may be used to monitor most any combustible gas.
Detcon catalytic bead sensors are specifically designed to be resistant to poisons such as sulfides, chlorides,
and silicones. The sensors are characteristically stable and capable of providing reliable performance for
periods exceeding 5 years in most industrial environments.
PGM 1
PGM 2
MODEL FP-624D HOUSTON, TEXAS
FLT 1 2 CAL
MicroSafe LEL Gas Sensor
ALM ALM
TM