Electrochemical Type: Gas diffuses through the back of a porous membrane into the working electrode of the sensor. Here, the gas is oxidized or reduced. This electrochemical reaction causes a change in the current flowing through the external circuitry. The gas concentration can be determined by measuring the magnitude of the current.
Catalytic Combustion Type: Catalytic combustion sensors are high-temperature sensors. The detection element is formed by coating a platinum wire coil (φ0.025~φ0.05) with alumina and binder to form a spherical shape, which is then sintered. Its outer surface is coated with a catalytic layer of rare metals such as platinum and palladium. When an electric current is passed through the platinum wire, the detection element is kept at a high temperature (300~400℃). If it comes into contact with a combustible gas, such as methane, the methane will burn on the catalyst layer. The combustion is essentially a reaction between the methane adsorbed on the element surface and the adsorbed oxygen ions. After the reaction, CO2 and H2O are generated and released, while the oxygen in the gas phase is adsorbed and dissociated by the element, replenishing the oxygen ions on the element surface. The method of measuring methane using a platinum wire coil is based on the principle of measuring the heat released during the combustion reaction of methane on its surface. Combustion raises the temperature of the platinum wire coil, increasing its resistance. Measuring the change in the platinum wire resistance indicates the concentration of the combustible gas.
Infrared method: Molecules composed of different atoms have unique vibrational and rotational frequencies. When exposed to infrared radiation of the same frequency, they absorb infrared light, causing a change in infrared intensity. Measuring this change in intensity allows for the determination of the gas concentration.
