Photoacoustic spectroscopy miniaturises CO2 sensor

21st June 2019
Alex Lynn

City dwellers often spend a large amount of their time indoors, either in an office, at school, or simply at home. Urbanised spaces, however, tend to trap and develop bad air quality as they get more insulated for energy efficiency purposes. The concentration of CO2 is an indicator for bad air quality. 

Today´s market solutions for monitoring this odourless and colourless gas are bulky and costly or simply not good enough for a widespread adoption. Infineon Technologies has developed a disruptive CO2 sensor technology based on the photoacoustic spectroscopy (PAS).

XENSIV PAS210 makes use of this new technology. It implements a high sensitivity MEMS microphone as a detector and enables significant miniaturisation of CO2 sensors. For this reason, it is ideal for smart home applications and building automation i.e. demand controlled ventilation, as well as various indoor air quality IoT devices such as air purifiers, thermostats, weather stations, and personal assistants. 

The sensor helps to improve the indoor air quality in a timely and energy efficient manner. Based on an extensive portfolio of patents around the PAS technology, PAS210 will not only enable high volume and cost sensitive CO2 sensing applications but will also pave the road for the detection of other gases in the future.

On a single PCB, the CO2 sensor integrates the photoacoustic transducer including the detector, the infrared source and the optical filter. It also holds a microcontroller for signal processing and algorithms as well as a MOSFET to drive an infrared source. 

All the components are developed and designed in-house according to Infineon´s high quality standards, leading to the best-in-class price/performance. For instance, XENSIV PAS210 uses the high SNR (Signal-to-Noise Ratio) MEMS microphone XENSIVE IM69D130 as a detector. The sensor thus benefits from Infineon´s long record of accomplishments in acoustic technology and related applications.

PAS210 is a real CO 2 sensor in an unprecedented small form factor, enabled by the unique PAS detection principle. The sensor saves more than 75% space in customer end products compared to commercially available real CO2 sensors. Its direct ppm readings, surface mounting capability and simple design allow for an easy and fast integration in low and high volume applications alike.

The integrated microcontroller converts the MEMS microphone output into a ppm reading, which is available either via the serial I²C, UART or PWM interface. XENSIV PAS210 CO 2 measurement capabilities cover a range from zero to 10,000 ppm with an accuracy of ± 30 ppm or ±3% of the reading. In a pulsed mode, the XENSIV PAS210 CO2 sensor is designed to have a lifetime of ten years.

The XENSIV PAS210 CO2 sensor will be showcased at Sensor+Test in Nuremberg and at Sensors Expo in San Jose (California), USA. Early samples are being validated in selected targeted applications. Engineering samples are planned to be available in the first half of 2020, Infineon aims at starting the production in the second half of the same year.

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