Fault Analysis of Combustible Gas Detectors Based on Principles
1. Combustible gas detector is a detector installed and used in industrial and civil buildings that responds to the concentration of single or multiple combustible gases. The commonly used combustible gas detectors in daily life are catalytic combustible gas detectors and semiconductor combustible gas detectors. Semi conductive combustible gas detectors are mainly used in places such as restaurants, hotels, and home workshops where gas, natural gas, and liquefied gas are used. Catalytic combustible gas detectors are mainly used in industrial places where combustible gases and vapors are emitted.
2. Catalytic combustible gas detector uses the resistance change of refractory metal platinum wire after heating to determine the concentration of combustible gases. When combustible gas enters the detector, it causes oxidation reaction (flameless combustion) on the surface of the platinum wire, and the heat generated increases the temperature of the platinum wire, causing a change in its electrical resistivity. Therefore, when encountering high temperature and other factors, the temperature of the platinum wire changes, and the electrical resistivity of the platinum wire changes, resulting in a change in the detected data.
3. The semiconductor type combustible gas detector uses the change in surface resistance of semiconductors to determine the concentration of combustible gases. The semiconductor combustible gas detector uses gas sensitive semiconductor components with high sensitivity. When it encounters combustible gas during operation, the semiconductor resistance decreases, and the decrease value corresponds to the concentration of combustible gas.
4. The combustible gas detector consists of two parts: detection and detection, with detection and detection functions. The principle of the detection part of the combustible gas detector is that the sensor of the instrument uses a detection element, a fixed resistor, and a zero potentiometer to form a detection bridge. The bridge uses platinum wire as a carrier for catalytic elements. After being powered on, the temperature of the platinum wire rises to the working temperature, and air reaches the surface of the element through natural diffusion or other means. When there is no combustible gas in the air, the bridge output is zero. When the air contains combustible gas and diffuses onto the detection element, flameless combustion occurs due to catalytic action, causing the temperature of the detection element to rise and the platinum wire resistance to increase, causing the bridge circuit to lose balance. As a result, a voltage signal is output, which is proportional to the concentration of combustible gas. The signal is amplified, analog-to-digital converted, and displayed on a liquid display to show the concentration of combustible gas. The principle of the detection part is that when the concentration of the combustible gas being measured exceeds the limit value, the amplified bridge circuit outputs a voltage and the circuit detection set voltage. Through the voltage comparator, the square wave generator outputs a set of square wave signals to control the sound and light detection circuit. The buzzer produces continuous sound, and the light-emitting diode flashes to emit a detection signal. From the principle of combustible gas detector, it can be seen that if electromagnetic interference occurs, it will affect the detection signal and cause data deviation; If there is a collision or vibration that causes the equipment to break, the detection will fail; If the environment is excessively humid or the equipment is flooded, it may also cause a short circuit in the combustible gas detector or a change in the resistance value of the circuit, resulting in detection failure.
