Types of Sensors for Gas Detection Instruments and Advantages and Disadvantages
A gas detector is an instrumentation tool for gas leakage concentration detection, mainly portable/handheld gas detectors. It mainly utilizes gas sensors to detect the type of gas present in the environment. Gas sensors are sensors that are used to detect the composition and content of gases. It is generally accepted that the definition of a gas sensor is based on the classification of the detection target, which means that any sensor that is used to detect the composition and concentration of a gas is called a gas sensor, regardless of whether it is used by a physical method, or by a chemical method. For example, sensors that detect gas flow are not considered gas sensors, but thermally conductive gas analyzers are important gas sensors, even though they sometimes use roughly the same detection principle.
Semiconductor
It is manufactured using the principle that the conductivity of some metal oxide semiconductor materials, at a certain temperature, changes with the composition of the ambient gas. For example, alcohol sensors are prepared using the principle that the resistance of tin dioxide decreases dramatically when it encounters alcohol gas at high temperatures.
Advantages
Semiconductor gas sensors can be effectively used to detect methane, ethane, propane, butane, alcohol, formaldehyde, carbon monoxide, carbon dioxide, ethylene, acetylene, vinyl chloride, styrene, acrylic acid, and many other gases. In particular, these sensors are inexpensive and suitable for residential gas detection needs. The following semiconductor gas sensors are successful: methane (natural gas, biogas), alcohol, carbon monoxide (city gas), hydrogen sulfide, ammonia (including amines, hydrazines). High quality sensors are available for industrial detection needs. INDUSTRIAL SCIENTIFIC, USA gas sensors
Disadvantages
Less stable and more affected by the environment; in particular, the selectivity of each sensor is not precise and the output parameters cannot be determined. Therefore, it is not suitable for application in places where measurement accuracy is required.
Combustion type
This sensor is in the platinum resistor surface preparation of high temperature resistant catalyst layer, at a certain temperature, combustible gases in its surface catalytic combustion, combustion is the platinum resistor temperature increases, resistance changes, the change value is a function of the concentration of combustible gases.
Advantages
Catalytic combustion gas sensors selectively detect flammable gases: whatever cannot be burned, the sensor does not respond. Catalytic combustion gas sensors are accurate in measurement, fast in response and have a long life. The output of the sensor is directly related to the explosion hazard of the environment and is a dominant class of sensor in the field of safety detection.
Disadvantages
No selectivity in the flammable gas range. Operating in a dark flame, there is a risk of ignition and explosion. Most elemental organic vapors are toxic to the sensor.
Thermal conductivity cell type
Each gas, has its own specific thermal conductivity, when two and more gases have a large difference in thermal conductivity, you can use the thermal conductivity element, to distinguish the content of one of the components. This type of sensor has been sensorized for hydrogen detection, carbon dioxide detection, and detection of high concentrations of methane.
This type of gas sensor can be applied in a narrower range and has more constraints.
