Dependent on the concentration of the gas detection gas detection transmitter, the sensor is part of the core, according to the different detection principle, be divided into metal oxide semiconductor sensors, catalytic combustion sensor, constant potential electrolysis gas sensors, Gideon Galvani Batteries Oxygen sensors, infrared sensors, PID photoionization sensors, the following briefly discusses the principles and characteristics of various sensors。
Metal oxide semiconductor sensors
Metal oxide semiconductor gas sensor using the measured adsorption, changes in the conductivity of the semiconductor, through the comparison of current change, inspire alarm circuit. Because the semiconductor sensor measurements influenced by the environment, the output linear instability. Metal oxide semiconductor sensors, because of their reaction is very sensitive, it is now widely used for measuring the field of micro-leakage phenomenon of gas。
Catalytic combustion sensor
Principle of catalytic combustion sensor is the most widely used principle of detection of combustible gas, with a good output signal linear, exponential, reliable, cheap, non-combustible gases and other non-cross-interference and so on. Catalytic combustion sensor using a Wheatstone bridge principle, sense resistor and the environment occurs in the flameless combustion of combustible gases, the temperature sensing resistor to change the bridge to break the balance, so that the output stability of the current signal, and then after post-amplification circuit, stable and reliable numerical processing of final display。
Potentiostatic electrolytic gas sensor
Constant potential electrolysis sensor is field testing the most widely used drug class, a technology, foreign technology leader in this area, so most of these sensors rely on imports. Potentiostatic electrolytic gas sensor structure: in a pool made of plastic tubular body, install a working electrode, counter electrode and reference electrode, filled with electrolyte between the electrodes, made from the porous PTFE membrane, the top of the package. Pre-amplifier and the sensor electrode connection is applied between the electrodes some potential, so that the sensor is in working condition. Gas and the working electrode within the electrolyte oxidation or reduction reaction occurs in the reduction or oxidation reaction of the electrode, the electrode potential change in the balance, change the value proportional to the concentration of gas。
Buddha Galvani cell type oxygen sensor
Caramel Galvani cell membrane type oxygen sensor structure: one side in plastic containers with good oxygen permeability, thickness 10 ~ 30μm breathable PTFE membrane, inside the container compact in its adhesion precious metals (platinum, gold , silver, etc.) cathode, the other side of the container or containers of spare parts inside of the formation of the anode (with lead, cadmium, the tendency of large metal ions). With potassium hydroxide. Oxygen in the anode through the electrolyte in the redox reaction of metal ions to the anode, releasing electrons current is proportional to the size and the amount of oxygen, due to the reaction of metal anodes are consumed, so the sensors need to be changed regularly. At present, technology has matured, the localization of these sensors can。
Infrared sensor
Infrared sensors use a variety of elements on a specific wavelength absorption principle, with good anti-toxic, responsive, a response in the majority of hydrocarbons. But the structure is complicated and costly。
PID Photoionization gas sensor
PID by the UV light source and ion chamber and other major parts, there are positive and negative electrodes in the ion chamber to form a field, tested gas in the irradiation of UV light, ionization, positive and negative ions generated in a current between the electrodes, the amplified output signal. PID is highly sensitive, non-toxic problems, safe and reliable。
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