Figure 5. SDC30 Figure 2. SGP41
also ensures reliability and accuracy over the lifetime of the equipment.
NDIR technology for CO2 sensing Non Dispersive InfraRed technology (NDIR) has become a preferred technique for measuring CO2 concentration. It is based on the principle of that CO2 molecules absorb infrared light with wavelength around 4.2 µm. The infrared light in the sensor is filtered and only the required wavelength passes to the air sample compartment where the CO2 molecules will absorb the light. The concentration of the CO2 will be proportional to the infrared light absorbed by the CO2 molecules. NDIR sensors can be divided into transmissive and photoacoustic technologies. The transmissive technology uses a photodetector to measure the infrared light which has not
photoacoustic NDIR technology. The SCD4x devices are next generation CO2 sensors which break previous size and cost barriers to revolutionise the CO2 sensing market. With an extremely small form factor (10.1mm x 10.1 mm x 6.5 mm), low power consumption and a competitive price point, the SDC4x boosts design freedom for customers.
Innovative OPC technology for Particulate Matter
Figure 6. SDC4x measurement Figure 3. Transmissive NDIR
The Sensirion PM sensors are optical particle counters (OPC) based on laser scattering. The principle of this technology consists of a laser beam which crosses the air sample flow and due to the interaction of particles and laser light, part of the light is scattered towards a photodetector. The signal from the photodetector is converted into mass concentration values. One of the main challenges of this technology can be the accumulation of particles on the photodiode over time which produces a drift effect. Sensirion have patented a contamination-resistance technology to eliminate this effect by protecting all the optical elements in the sensor with a clean air flow ensuring that there is no drift of the measurement over time and importantly no maintenance is required. The Sensirion SPS30 sensor provides PM measurement with mCerts certification. The contamination resistance technology enables long term stability and precise measurement over the lifetime of more than ten years for this device. The advanced algorithms embedded on the device provide an accurate measurement (PM 2.5 ± 10µg/m3 @ 0 – 100 µg/m3 and ± 10% @ 100 to 1000 µg/m3). Its small size (40.6 x 40.6 x 12.2 mm) makes it easy to integrate in application where size and space are limited and provides different interfaces including UART and I2C.
Figure 4. Photoacoustic NDIR
been absorbed by the CO2 molecules. The higher the signal from the photodetector, the lower the concentration of gas. Photoacoustic technology uses a microphone to detect CO2. The CO2 particles vibrate when they absorb light, and this vibration generates waves that can be measured by a sensitive microphone. The higher the signal measured by the microphone, the higher the concentration of CO2. Sensirion has developed CO2 sensors based on both different NDIR technology approaches.
The SDC30 is a dual channel transmissive NDIR CO2 sensor which uses two photodetectors to minimize drifting effects. SDC30 offers accurate and stable C02 measurement in addition to long-term stability. The small module size allows convenient integration into different applications. The SDC4x series are based on Sensirion’s patented PASens
www.cieonline.co.uk
All-in-one air quality sensor by Sensirion Some applications require accurate monitoring and measurement of multiple air quality parameters. This presents its own challenges as integrating the different sensors
required involves more complex development and longer design time, for these applications physical
Figure 8. SPS30
size and available space can also be a limiting factor. Sensirion now offer a viable alternative to multiple air sensor integration with the launch of the SEN5x, a complete environmental node sensor solution. This all-in-one platform provides accurate measurement of key air quality parameters such as PM, VOC, NOx, humidity and temperature, all integrated in one compact device. This high level of integration allows reduction of design time and complex development leading to an all-important faster time to market for their products.
Figure 9. SEN5x
Thanks to proprietary Sensirion technologies and algorithms, the SEN5x provides accurate and reliable measurements over time for the different air quality parameters making it the perfect sensor for devices such as air purifiers, air quality monitors, HVAC systems and ventilation systems. The device is available in three variants, SEN50 (PM-only), SEN54 (PM, VOC and RHT) and SEN55 (PM, VOC, NOx and RHT).
Conclusion
No matter what air quality pollutant your application needs to detect or measure, Sensirion have the innovative leading edge technology solutions to suit.
Design support
Anglia offers support for customer designs with free evaluation kits, demonstration boards and samples of Sensirion products via the EZYsample service which is available to all registered Anglia Live account customers. Anglia’s engineering team are also on hand to support designers with air quality sensor designs and can offer advice and support at component and system level. This expertise is available to support customers with all aspects of their designs, offering hands on design support along with access to additional resources from Sensirion such as technical application notes and reference designs. Scan the QR code or visit
www.anglia-live.com to see the full range of Sensirion products available from Anglia.
Figure 7. Sensirion’s patented contamination-resistance technology
Components in Electronics November 2022 11
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