Combustible gas detector is a kind of detection device which is installed and used in industrial and civil buildings to respond to single or multiple combustible gases. According to the types of sensors, it is mainly divided into two categories: catalytic combustion type and semiconductor type.
Catalytic combustion combustible gas sensor is used to measure the concentration of combustible gas by the change of resistance of refractory metal platinum wire after heating.
When combustible gas enters the detector, it causes oxidation reaction (flameless combustion) on the surface of platinum wire, and the heat generated increases the temperature of platinum wire. When the temperature changes, the resistance value of platinum wire also changes. The detector determines the concentration of test gas by collecting the change rate of resistance value of platinum wire.
Semiconductor type combustible gas sensor is used to measure the concentration of combustible gas by the change of semiconductor surface resistance.
When the combustible gas touches the semiconductor surface and is adsorbed, the adsorbed molecule spreads freely on the surface of the object, which makes the semiconductor resistance change. The detector determines the concentration value of the combustible gas according to the change of the semiconductor resistance value.
The catalytic combustion combustible gas sensor is accurate in measurement, fast in response, and has a long life. It is a kind of dominant sensor in the field of safety detection, and most combustible gas detectors adopt this kind of sensor. Since its working principle is catalytic combustion, all the gases that can be burned can respond, while the gases that cannot be burned have no response.
Semiconductor sensors have low cost and are suitable for civil gas detection and each sensor can only detect one corresponding combustible gas, the output parameters can be determined, unlike catalytic combustion sensor in the range of combustible gas without selectivity. The disadvantage is poor stability, greatly affected by the environment.
Combustible gas detector is divided into detection and detection two parts, just talk about the sensor belongs to the detection part, now let's talk about the detection part of the instrument.
The principle of the detection part of the combustible gas detector is that the sensor of the instrument adopts the detection element, fixed resistance and zero potentiometer to form the detection bridge. The bridge USES platinum wire as the carrier of the catalytic element. After electrification, the temperature of platinum wire rises to the working temperature, and air reaches the surface of the element by means of natural diffusion or suction pump.
When no combustible gas in the air, bridge circuit output is zero, when the air contains flammable gases and spread onto the detecting element, because the flameless combustion catalyst, temperature, detection element, platinum resistance increases, the bridge road out of balance, to have a voltage signal output, the size of the voltage is proportional to the concentration of combustible gas, signals are amplified and modulus conversion, through the display panel to show the density of combustible gases.
Above relevant knowledge of gas detector, hope it is useful for you.
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