Operating Principle ‐MOS Type Gas Sensor

In the case of “what can a typical multiple gas detector monitor?”, common monitored substances are hydrogen sulfide, carbon monoxide, oxygen and flammable gases. Multi-gas detectors can detect carbon dioxide, sulfur dioxide, gas detection equipment ammonia, chlorine, VOC and many other gases, depending on the sensor configuration. Low-power infrared sensors measure trace gases by determining the absorption of an infrared light source emitted by an air sample.

Some models of more advanced gas transmitters also have a digital measurement display, alarm relay for controls, MODBUS communication or even TCP/IP communication for the most powerful. Public awareness of the dangers of indoor carbon dioxide has increased, and portable CO2 gas detectors have become increasingly popular. Due to the principle of absorption of the infrared light source, carbon dioxide gas is detected in the scene environment and people are reminded to open the windows to ventilate in time.

This information will help you determine which one is best suited to keep your workplace and employees safe.

It is the current way for the industry to warn of phosphineegas accidents. The H2 portable gas detector is an instrument used to detect the concentration of hydrogen in the environment. Using imported electrochemical sensors, it has excellent sensitivity and repeatability.

The unit of measurement is volume percentage for flammable gases, ppm or mg/m3 for low concentration gases. These detectors give a first idea of the composition of gas in an area. They allow measurements at numerous points and numerous gases, but there are only periodic and limited measurements.

Exposure to toxic gases can also occur in activities such as painting, fumigation, fuel filling, construction, excavation of contaminated soils, landfill operations, access to confined spaces, etc. Common sensors include flammable gas sensors, photoionization detectors, infrared spot sensors, ultrasonic sensors, electrochemical gas sensors, and metal oxide semiconductor sensors. A fixed gas detector – or gas transmitter – is a gas sensor dedicated to measuring gas concentrations in the air and forms the first element of a fixed gas detection installation. There are many sensors available for the detection of explosive flammable gases, toxic gases, volatile organic compounds, suffocating gases or freons. When the gas concentration exceeds the set alarm value of the sensor, the gas detector emits an audible alarm, displays a visible alarm and indicates the gas concentration measured on the gas detector display.

They can classify detected gas samples into hydrogen, methane, light gas, medium gas or heavy gas. They are not susceptible to poisoning even when exposed to high concentrations of dangerous gases. As described above, MOS-type gas sensors change resistance due to a change in the concentration of adsorbed oxygen. If used correctly, reducing gases such as carbon monoxide can be detected. The adsorbed oxygen formed in clean air will be consumed in contact with carbon monoxide, the resulting decrease in R will be used to estimate the concentration of carbon monoxide. The sensor regains its original resistance level when the carbon monoxide is turned off.

Such a detection mechanism is operational in gas sensors based on tin dioxide. The measuring range for the detector shall be taken into account and the alarm levels shall comply with the requirements of HSE/COSHH/DSEAR. In some cases, the detectors can function as stand-alone devices with their own built-in alarms and audible visual displays.

IR hydrocarbon gas detectors can be classified into two types known as point detectors and open pad detectors. For point detectors, the length of the absorption path is fixed, and the instrument design determines that it is a few centimeters. For open-path IR detectors, the length of the absorption path can be as long as 130 meters instead of the few centimeters of the point detector. The multi-gas detector is an instrument and equipment for detecting a variety of gases. When two or more gases need to be monitored in the working environment, a multi-gas detector is required. Usually, the gases detected by multigas detectors are mainly CO, H2O, O2, SO2, NH3, CL2, etc.