General Topic: CMOSens® Technology
All Sensirion products are characterized by the fusion of the sensor element and the signal conditioning electronics on a single silicon CMOS chip.
Example: CMOSens® in Gas Sensing
Using Sensirion’s CMOSens® Technology, the SGP gas sensor offers a complete sensor system on a single chip featuring a digital I2C interface, a temperature-controlled microhotplate, as well as fully processed and calibrated indoor air quality signals.
Metal-Oxide Based Gas Sensing Principle
Metal-oxide gas sensors are based on a film of metal-oxide particles between two electrodes, on top of a hotplate for heating purposes. Heating the metal-oxide to high temperatures yields negatively charged oxygen species absorbed at the metal-oxide surface. The surface oxygen species react with ambient target gases and thereby release electrons into the metal-oxide film resulting in a change of electrical resistivity of the metal-oxide layer. The change of resistivity is measured between the two electrodes and directly depends on the ambient target gas concentration. Gas sensors with Sensirion’s MOXSens® technology measure the analog metal-oxide resistivities as function of ambient gas concentrations and provide fully processed, calibrated and digitalized indoor air quality signals.
Advantages of Metal-Oxide Technology
Biggest advantage of a metal-oxide gas sensor is the high sensitivity to a large variety of gaseous compounds. The limits of detection range around very small concentrations, depending on the measured target gases, from a few parts per million (ppm) down to parts per pillion (ppb). By integrating into small packages, CMOSens® metal-oxide sensors become a cost-effective and sensing technology, which is suitable for mass production and regarding high-volume applications.
SGP – A Gas Sensor System on a Chip
The multi-pixel gas sensor platform integrates four metal-oxide sensing elements – the pixels – into a very small 2.45 × 2.45 × 0.9 mm3 DFN package. Using Sensirion’s CMOSens® Technology, the SGP offers a complete sensor system on a single chip featuring a digital I2C interface, which can be connected directly to any microprocessor system and thereby allows for time efficient and cost effective integration. A temperature-controlled micro-hotplate assures stable operation of the four individual sensing pixels. On-chip algorithms for baseline, temperature and humidity calibration transform the sensor pixel signals into preprocessed and calibrated digital signals, such as ambient VOC concentration and equivalent concentration of CO2. As the first metal-oxide gas sensor featuring multiple sensing elements on one chip, the SGP30 provides more detailed information about the air quality.