MEMS-based MiCS-5524: early fire detection MOS gas sensors from SGX Sensortech
The MiCS-5524 VOC/CO dual gas sensor is a MEMS-based MOS gas sensor with a thin gas sensing layer that is highly selective and very responsive to reactive (reducing) and oxidising gasses. These features are essential in a fire detection system, where every second counts in order to prevent irreparable damage.
Unsafe installations and unpredictable environments expose people, valuable assets, business processes and more to the risk of fire. Early fire detection minimises the impact of damage by allowing immediate and effective measures to be taken before a fire spreads. The MiCS-5524 VOC/CO sensor can be used in conjunction with certified gas sensors that are often slow to respond – the MiCS-5524 VOC/CO can detect gases in less than a second.
SGX and other MOS gas sensors rely on detection of changes in resistance in the sensing layer in the presence of the target gases. For oxidising gases, such as ozone or nitrogen dioxide, the resistance will increase; for reducing gases, such as carbon monoxide or VOCs, it will decrease. In very simple terms, reducing gases remove some of the ‘insulating’ oxygen species at the grain boundaries, which reduces overall resistance. The opposite is true of oxidising gases, which add to the insulating oxygen species. These reactions occur at elevated temperatures, so the sensing layer must be heated with the integrated heater. One of the main advantages of the SGX sensor is that it requires less power than other types of sensors to heat and run. Changes in resistance is not a linear response to the change in gas concentration; rather, it is a polynomial relationship. This, and other factors, means that the sensors are most suitable for the detection of the presence of gas or changes in gas levels, rather than an analysis with high accuracy, for which other more sophisticated systems are available. The sensor is ideal as an early detector for gases emitted from a fire.