Combustible gas detectors are detectors installed in industrial and civil buildings that respond to single or multiple concentrations of combustible gases.The most commonly used combustible gas detector is catalytic combustible gas detector and semiconductor combustible gas detector.

Hotels, hotels, domestic production rooms and other places that use gas, natural gas, liquefied gas mainly use semiconductor combustible gas detector, the emission of combustible gas, combustible steam industrial sites mainly use catalytic combustible gas detector.

Catalytic combustible gas detector is used to measure combustible gas concentration by changing the resistance of refractory platinum wire after heating.

When the combustible gas into the detector, the platinum surface cause oxidation reaction (flameless combustion), raise the temperature of the heat makes the platinum wire, and platinum resistivity change, so when high temperature change when factors such as the temperature of the platinum wire, and platinum resistivity change and detecting data will also change.

Semiconductor combustible gas detector is used to measure combustible gas concentration by the change of semiconductor surface resistance.

The gas sensitive semiconductor element with high sensitivity is used in the semiconductor combustible gas detector. When it encounters combustible gas in the working state, the semiconductor resistance drops, and the drop value has a corresponding relationship with the combustible gas concentration.

The combustible gas detector consists of two parts: detection and detection.

The principle of the inspection part of the combustible gas detector is that the sensor of the instrument consists of the inspection element, the fixed resistance and the zero potentiometer. The bridge is catalyzed by platinum wire as carrier. After electrification, the platinum wire temperature rises to the operating temperature, and air reaches the surface of the element by natural diffusion or other means.

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, signal amplifying, modulus conversion, through liquid display shows the concentration of combustible gas.

Electrochemical gas detector is a kind of gas detector using electrochemical sensor. Many gases have electrochemical activity and can be oxidized or reduced by electrochemistry, and the current generated by this reaction is proportional to the concentration of the reaction gas. Therefore, the composition and concentration of the gas can be detected by this kind of reaction.

This kind of detection method has high accuracy and quick response, which is mostly used for the detection of toxic gases. However, there are also different classifications of electrochemical reactions. The following are several electrochemical reaction modes and principles most commonly used by electrochemical gas detectors.

1. Constant potential electrolysis type. This method is currently the most widely used toxic gas detector, such as carbon monoxide detector. It is by installing the working electrode with constant potential in the electrolyte, the gas will react with oxidation or reduction at the working electrode, and then it will react with reduction or oxidation to the electrode, the potential of the electrode will change, the resulting current will be proportional to the concentration of the gas, and finally the concentration value will be obtained.

2. Galvanic battery. It's like a dry battery, except the battery is a carbon and manganese electrode, and this is a gas electrode, where the gas is reduced at the cathode, the electrons that are formed are oxidized to the lead at the anode, and the resulting current is proportional to the concentration of the gas, which is also calculated by the current.

3. Concentration battery type. On both sides of the electrochemical cell, the measured gas will spontaneously form a concentration difference electromotive force. The size of the electromotive force is related to the concentration of the gas.

4. Limit current type. This way is mainly oxygen sensor, used for the oxygen detection of the car, is a necessary instrument for the car. The limiting current is obtained by controlling the oxygen supplied to the cathode by gas diffusion, and the oxygen concentration is calculated by the limiting current.

Working principle of electrochemical sensor of gas detector:

Outside gas into the gas detector, gas into the sensor through the teflon film to an electrode, according to the different gas produces different electrochemical reaction, such as carbon monoxide gas to an electrode become carbon dioxide will be after oxidation, oxidation reaction through electronic open circuit from the working electrode to plate, a current, and the gas concentration is proportional to each other, then the gas detector to test the current amplifier, internal output measurement, after the last gas concentration on the screen.

Notes for use of portable gas detector

With the development of economy and the improvement of people's living standards, people are also paying more and more attention to health and safety issues. In addition to paying attention to the safety of daily life, diet and living, the hazards of gas are gradually taken seriously by people.

Especially industrial toxic or harmful gases, so many enterprises for the protection of poisonous gas had taken many protective measures, such as in the operations in which toxic gas environment employees need to wear the corresponding gas masks, protective clothing, in the device interface, the valve installation fixed try to gas detector, using portable gas detector on a regular basis to detect the concentration of harmful gas in air in a particular area records;

The selection of gas detector should be based on the specific situation, the selection of suitable detection equipment, use should also pay attention to the four major issues:

1, to pay attention to the instrument's service life is different gas detector, its service life is not the same, when buying to ask clear instrument service life, use in the shelf life, in order to save the cost of some enterprises, a detector used for several years not to replace, gas detection is just appearance, will eventually harm others.

2, pay attention to the interference of gas gas detection instrument is typically used when we detect gas leakage single gas detector to detect a particular gas, but often not only there is a gas in the test environment, so we should pay attention to other gases will for detecting instrument is causing interference to make test results is not accurate.

3, attention should be paid to the concentration of the gas detector to detect range before detection, in addition to estimate in advance according to the experience of the kinds of poisonous and harmful gas, but also estimate about the gas concentration, tested by gas detector set alarm value, when the gas concentration is beyond the scope instrument testing, to close the detector, gas detector long range of test conditions can cause serious damage to the instrument, will cause the test inaccurate or discarded directly.

4, to pay attention to the maintenance of the instrument gas detector, like other equipment, also pay attention to the regular maintenance, to carry out irregular calibration and testing, stored in a low temperature environment, to extend its service life.

The principle of detecting part is when the concentration of combustible gas being measured exceeds limit, after amplification of bridge circuit output voltage and set the voltage detection circuit, through the voltage comparator, square wave generator output a square wave signals, sound control, light detection circuit, buzzer sound continuously, light-emitting diodes, signal detection.

It can be seen from the principle of combustible gas detector that if there is electromagnetic interference, the detected signal will be affected and data deviation will occur. In case of collision or vibration, the device will break off, which will cause detection failure; If the environment is too wet or the equipment is filled with water, it may also cause a short circuit in the combustible gas detector, or a change in the line resistance value, the detection failure.