Detect the concentration of the gas depends on gas detection transmitter, sensor is its core part, depending on the detection principle, mainly divides into the metal oxide semiconductor sensor, catalytic combustion type, constant potential electrolysis sensor type gas sensor, and she battery type oxygen sensors, infrared sensor, PID ionization sensors such as light, simple principle and characteristics of various sensors.

Metal oxide semiconductor sensor

The metal oxide semiconductor sensor changes the conductivity of the semiconductor by using the adsorption action of the gas under test.

The output line shape is unstable because of the environment influence of semiconductor sensor.

The metal oxide semiconductor sensor, because of its very sensitive reaction, is widely used in measuring gas leakage.

Catalytic combustion sensor

Catalytic combustion type sensor principle is one of the most widely used the principle of detection of flammable gas, has good linear output signal, reliable index, the price is cheap, no cross interference with other non combustible gas, etc.

Catalytic combustion type sensor using wheatstone bridge principle, induced resistance and environment of the combustible gas flameless combustion, that temperature sensing resistance value changes, break the bridge balance, stable output current signal, after amplification circuit, stability and handling late eventually shows reliable numerical values.

Potentiometric electrolytic gas sensor

Potentiometric electrolytic sensor is one of the most widely used technology in the field of poison measurement at present, and it is the leading technology in foreign countries. Therefore, most of these sensors are imported.

Structure: the constant potential electrolysis type gas sensor inside a plastic tubular pool, installation work electrode, the electrode and reference electrode, filled with electrolyte between the electrodes, made from porous tetrafluoroethylene diaphragm, encapsulated at its top.

The connection between the preamplifier and the sensor electrode exerts a certain potential between the electrodes to keep the sensor in working state.

Gas in the electrode and electrolyte work oxidation or reduction, the electrode reduction or oxidation reaction occurs, the balance of the electrode potential changes, changes in value is proportional to the gas concentration.

Cavani battery oxygen sensor

Diaphragm and she battery type oxygen sensor structure: on one side of the plastic container is equipped with the oxygen permeability good, 10 ~ 30 microns thick teflon breathable membrane, tight adhesion of precious metals in its container inside (platinum, gold, silver, etc.) Yin electrode, on the other side of the container inside or container of spare parts to form the anode (with ionization tendency big metal such as lead, cadmium).

We use potassium hydroxide.

When oxygen through the electrolyte in anode oxidation reduction reaction, make the anode metal ionization, release the electrons, the size of the current proportional to how much oxygen, due to the reaction of metal anode consumption, so the sensors need to be replaced regularly.

At present, the domestic technology has become more and more mature, and it can completely produce such sensors domestically.

Infrared sensor

Infrared sensors take advantage of the absorption principle of various elements to a specific wavelength, with good anti-toxicity, sensitive reaction and most hydrocarbons.

But the structure is complex and the cost is high.

PID photoionization gas sensor

PID by ultraviolet light source and ion chamber main parts, such as the ion chamber has positive and negative electrodes, electric field, gas under test under the irradiation of ultraviolet lamp, ionization, generate positive and negative ions, electric current is formed between the electrode and the amplifier output signal.

PID has the advantages of high sensitivity, no poisoning problem, safety and reliability.