Indoor air quality sensor uses fusion algorithms

ScioSense, a manufacturer of integrated environmental and flow sensors, has implemented a new multi-element sensing architecture for its next generation of air quality sensors using four highly integrated MEMS micro-hotplates, and developed sensor fusion technology which synthesises the signals from each sensing element while compensating for the effect of humidity.

This new technology underlies an industry-best Automatic Baseline Correction function, which intelligently resets the local threshold for air quality to ensure that the ENS160 reliably detects changes to pollution levels and odors in indoor air, no matter where in the world it is located. Intelligent sensor fusion is also the key to an enhanced carbon dioxide equivalents (eCO2) score, which takes account of the range of polluting or odorous gases generated by human activity in addition to exhaled CO2.

These advanced features, unique to the ENS160, mean that its air quality indicators much more closely reflect the effect of airborne pollutants and odors on occupants of indoor space. Systems such as air purifiers, demand-controlled ventilation, cooker hoods and smart home hubs based on the ENS160 can perform more accurate monitoring of indoor air. This means that users can enjoy clean and fresh air at all times while avoiding the waste of money and energy incurred when running air-cleaning equipment unnecessarily.

The new micro-hotplates and intelligent operating controls also provide high immunity to contamination by siloxanes, ensuring a long operating lifetime in any indoor residential, commercial, professional or in-cabin automotive setting.

Dirk Enderlein, CEO at ScioSense, said: ‘When ventilation or air-cleaning equipment stops running because the air-quality monitoring system has failed to detect human body odors, or has its baseline for air quality set too high, it has a real effect on the occupants of indoor spaces. It impairs the ability of school students to focus on their lessons, it puts people at risk of long-term harm caused by pollution, and it makes our living spaces less pleasant to work or relax in. Offering a unique combination of high broadband gas sensitivity and intelligent selectivity, the ENS160 enables ventilation and air cleaning systems to be used in the right way at the right time, to improve the quality of life for people indoors.’

Three types of accurate air quality output

The multi-element TrueVOC technology on which the ENS160 is based is sensitive to oxidising gases such as ozone which affect the quality of indoor air, as well as to a wide range of volatile organic compounds (VOCs) such as toluene, ethanol, methane, sulfur dioxide and carbon monoxide. The algorithms supplied with the ENS160 produce three measurement outputs:

• Total VOCs (TVOC), which draws on the broad sensitivity of the ENS160 to human-generated and artificial VOCs
• eCO2, a commonly used proxy measurement for the density of human occupation of an indoor space
• Various air quality indexes which are compatible with international standards

The ENS160 also provides its raw gas measurements for OEMs which want to apply proprietary algorithms.

Other improvements in the ENS160 have reduced its start-up time on first use and warm-up time after each power-on, making the ENS160 the fastest air quality sensor on the market and the ideal choice for systems requiring fast responsiveness and an exceptional user experience. 

The sensor is housed in a surface-mount package which measures just 3mm x 3mm x 0.9mm, making the ENS160 the smallest fully integrated, reprogrammable air quality sensor in the market, suitable for integration into highly space-constrained designs, including in consumer products.

The ENS160 provides its measurement outputs to a host controller via a serial peripheral or I2C interface. Since all the sensor’s measurement algorithms run on-chip, there is no processing overhead on the host.

ScioSense also supplies an analog version, the ENS145, which is based on the same micro-hotplate technology that the ENS160 uses. It is intended for distributed system designs in which a central host fully controls the measurement outputs derived from the gas sensor inputs that the ENS145 provides.

Product samples and evaluation kits will be available on request from ScioSense and authorised distributors in Q1 2021.