Multi Gas Detector for 2~8 Gases

The core of a multi-gas detector lies in its built-in sensor components. These gas sensors collect information about gases in the environment and convert it into electrical signals for processing.

Depending on the gas being detected, multi-gas detectors employ different detection technologies, including but not limited to catalytic combustion, electrochemistry, infrared (NDIR), PID (photoionization detection), thermal conductivity, and optical waveguides.

The application of these principles enables multi-gas detectors to sensitively and accurately detect combustible and toxic gases in the environment, thereby issuing timely alarms and ensuring the safety of personnel and property.

1. Catalytic Combustion Principle

Catalytic combustion gas detectors utilize the oxidation reaction of combustible gases on the surface of a catalyst, generating heat that raises the sensor temperature, causing a change in resistance. By measuring this change in resistance, the concentration of the combustible gas can be determined.

They offer high sensitivity and fast response for combustible gas detection, but are susceptible to poisoning and ineffectiveness caused by impurities such as sulfides.

2. Electrochemical Principle

Electrochemical gas detectors generate a current proportional to the gas concentration through an electrochemical reaction with the gas being detected, converting the gas concentration into an electrical signal.

The gas being detected first passes through a tiny capillary opening and reacts with the sensor, generating a current or voltage signal proportional to the concentration of the target gas.

Electrochemical sensors feature low power consumption, excellent linearity and repeatability, long life, good selectivity, and high sensitivity, making them widely used in the detection of toxic and hazardous gases. However, their disadvantage is their relatively short lifespan and the need for regular electrolyte replacement.

3. Infrared Principle

Infrared sensors are gas sensors based on infrared spectroscopy. It detects target gases by exploiting the varying degrees of infrared absorption by different gases. When the target gas absorbs infrared light, it causes a change in light intensity, which the detector converts into an electrical signal.

Infrared-based gas detectors offer advantages such as a wide measurement range, high accuracy, and excellent stability, making them particularly suitable for measuring high-concentration, stable gases. However, they are costly and relatively insensitive to low-concentration gases.

4. Photoionization (PID) Principle

Photoionization gas detectors use an ultraviolet light source, which excites chemicals to produce positive and negative ions, which are detected by the detector. When molecules absorb high-energy ultraviolet light, they ionize, generating an electrical current that is amplified by the detector, resulting in a ppm-level concentration displayed on the surface.

PID sensors offer extremely high sensitivity and fast response for detecting trace gases such as volatile organic compounds (VOCs). They can detect a wide range of gases without causing permanent damage, facilitating subsequent analysis. However, their response to different gases varies, requiring calibration for each gas, and they are significantly affected by other interfering gases in the environment.

5. Thermal Conduction Principle

Thermal conduction gas detectors analyze the concentration of the measured gas by measuring changes in the thermal conductivity of the gas mixture. Typically, the difference in thermal conductivity of a thermal conduction gas sensor is converted into a change in resistance through an electrical circuit, thereby determining the concentration of the measured gas.

Detectors based on this principle offer advantages such as a wide detection range, high stability, and a long service life. They are widely used to detect high concentrations of gases such as methane, hydrogen, acetylene, and propane.

6. Semiconductor Principle

Semiconductor gas detectors utilize the adsorption of the measured gas to change the conductivity of a semiconductor, activating an alarm circuit by comparing the current change.

Semiconductor sensors offer advantages such as small size, light weight, low power consumption, and low price. However, their output linearity is unstable and significantly affected by the environment. Currently, they are widely used to measure micro-leakages.

As can be seen from the above introduction, gas detectors operate on a variety of principles, each with its own specific application scenarios, advantages, and disadvantages. When selecting a gas detector, you should consider various factors based on your actual needs and operating environment to select the most appropriate detection principle and model.