State-of-the-art CO2 sensors such as Sensirion’s SCD30 are based on the optical "Non Dispersive Infra-Red (NDIR)" sensing principle. Usage of these NDIR sensors is limited to just a few applications and low volumes due to their size and cost.
The sensitivity of a sensor based on the NDIR principle is directly proportional to the optical beam path. Therefore extensive shrinking of the sensor element results in compromising the sensor performance. Furthermore, NDIR based sensors don’t have a cost-effective BOM structure due to their size, structure and large amount of discrete components.
That is why Sensirion is revolutionizing the CO2 sensor market with the new SCD40 sensor relying on Sensirion’s unique PASens® Technology. PASens® Technology is based on the photoacoustic sensing principle. The photoacoustic sensing principle allows extreme miniaturization of the CO2 sensor without compromising sensor performance. This is due to the fact that the sensor sensitivity is independent of the optical cavity size. Furthermore the number of components is drastically reduced resulting in a highly price-efficient BOM and economic prices. Thanks to the miniaturization and the favorable BOM structure of this new CO2 sensor, the SCD40 will open up numerous possibilities for a whole new set of products and high-volume applications.
The photoacoustic effect was already discovered in 1880, but was not applicable for sensors due to missing technological components. Photoacoustic lab scale instruments on the other hand are well-established owing to their excellent performance. Thanks to Sensirion’s profound expertise in miniaturizing sensors (CMOSens® Technology) it was possible to develop the PASens® Technology, enabling a break-through step in miniaturizing the photoacoustic sensing principle. Critical components were developed in-house to ensure highest performance while remaining price-effective.
Narrow-band light matching the absorption bands of CO2 molecules is emitted into a predominantly closed measuring cell. CO2 molecules in the measuring cell absorb a part of the irradiated light, whereas other molecules cannot contribute to absorption due to the spectrum of the emitted light. The more molecules present in the measuring cell, the larger the absorbed energy. The absorbed energy of the CO2 - molecules excites mainly molecular vibrations, which results in an increased translational energy of the molecules and, due to the closed measuring cell, in an increase of pressure in the cell. A modulation of the light source causes a periodic pressure change in the measuring cell, which can be measured with a microphone. The signal of the microphone thus serves as a measure of the number of CO2 molecules present in the measuring cell and can be used to calculate the CO2 concentration.
CO2, Humidity and Temperature Sensor SCD40
Sensirion once again proves to be a pioneer in innovation for environmental sensor solutions: The SCD40 represents the first CO2 and RH/T sensor in miniature format, which impresses with a space requirement of only one cubic centimeter. This disruptive innovation is based on Sensirion's PASens® Technology and combines minimum size with maximum performance. The SCD40 opens up numerous new possibilities for integration and application. Because of its unmatched size and its unprecedented price-performance ratio, the SCD40 is the sensor of choice for today’s and future CO2 sensing markets such as IoT, automotive, HVAC, appliances and consumer goods. Click here to learn more about the SCD40.