What is the working principle of common gas detectors
(1) The combustible gas detector adopts a new generation of low-power and high anti-interference carrier catalytic sensors. It forms a detection bridge circuit with two fixed resistors. When combustible gases in the air diffuse to the surface of the detection sensor, they rapidly undergo flameless combustion under the action of the catalyst on the sensor surface, generating reaction heat that increases the platinum wire resistance value of the sensor. The detection bridge circuit outputs a differential pressure signal. The magnitude of this voltage signal is directly proportional to the concentration of combustible gases. After amplification, it undergoes voltage current conversion and converts the percentage content (% LEL) within the lower explosive limit of combustible gases into a 4-20mA standard signal output.
(2) The oxygen detector applies the principle of Gavanni primary battery, which is constructed by installing an anode (lead) and a cathode (silver) inside the primary battery, separated from the outside by a thin film. When oxygen-containing gas in the air passes through this film and reaches the cathode, an oxidation-reduction reaction occurs. At this point, the sensor will have an mV level voltage output that is directly proportional to the oxygen concentration. After amplification, this voltage signal will be converted into voltage and current, and the oxygen content within a percentage (0-30%) will be converted into a 4-20mA standard signal output.
(3) The toxic and harmful gas detector adopts advanced imported electrochemical sensors in the world, which apply the principle of controlled potential electrolysis. Its structure is to place three electrodes in the electrolysis cell, namely the working electrode, the counter electrode, and the reference electrode, and apply a certain polarization voltage. By replacing the sensors for different gases and changing the polarization voltage value, different toxic and harmful gases can be measured.
The measured gas reaches the working electrode through the thin film and undergoes an oxidation-reduction reaction. At this time, the sensor will have a small current output, which is proportional to the concentration of toxic and harmful gases. This current signal is converted into voltage after sampling and processing. The voltage signal is then amplified and subjected to voltage current conversion. The content (ppm value) within the detection range of toxic and harmful gases is converted into a 4-20mA standard signal output.
Organic volatiles are detected using the world's high-quality photo ion gas sensor (PID), which uses the principle of photo ion ionization gas for gas detection. Specifically, the ultraviolet light generated by an ion lamp is used to irradiate/bombard the target gas. After absorbing sufficient ultraviolet light energy, the target gas will be ionized. By detecting the small current generated after gas ionization, the concentration of the target gas can be detected.
(4) The carbon dioxide detector adopts the world's advanced infrared principle sensor, which utilizes the physical properties of infrared to measure. It includes an optical system, detection components, and photoelectric detection components. Optical systems can be divided into two types according to their structure: transmissive and reflective. Detection components can be divided into thermal detection components and photoelectric detection components according to their working principles. The most commonly used thermistor is the thermistor. When a thermistor is exposed to infrared radiation, the temperature increases and the resistance changes, which is converted into an electrical signal output through a conversion circuit.
