Miniature CO2 sensors break size barrier

27th April 2023
Mick Elliott

Sensirion has launched the SCD4x series of next generation miniature CO2 sensors along with an evaluation kit SEK-SCD41 which helps developers accelerate their designs.

The sensor and evaluation kit are available from distributor Anglia Components.

This sensor builds on the photoacoustic sensing principle and Sensirion’s patented PASens and CMOSens technology to enable small sensor size combined with high performance.

As people across the world return to public areas such as the work place and schools despite the coronavirus pandemic, this can present some issues as many of these environments are often enclosed or potentially poorly ventilated spaces where occupants can be sitting side by side for several hours. This raises concerns about virus transmission.

Tiny droplets (known as aerosols) are emitted not only when people cough or sneeze, but also during normal breathing and speech. These aerosols may contain viruses, which is why frequent and effective ventilation of enclosed spaces is more important than ever. The more fresh air there is in a closed room, the less exhaled air which may contain viruses.

Various solutions for regular ventilation in enclosed spaces exist and by far one of the most effective indicators that a space needs ventilating is to measure the CO2 level

This is where modules equipped with Sensirion CO2 sensors can be used to effectively measure air quality in enclosed spaces.

A CO2 warning system is easy to use, intuitively understandable thanks to the traffic light system, and measures with high accuracy. It ensures regular and effective ventilation, so occupants have the confidence to return to these spaces. In addition to reducing the risk of transmitting viruses such as COVID-19, CO2 reduction measures also increase concentration capacity – another positive effect.

The SCD4x miniature CO2 sensors are compatible with SMD soldering processes and feature a small footprint allowing cost and space-effective integration to boost freedom of design for customers.

What is said to be a best-in class humidity and temperature sensor enables superior on-chip signal compensation and addition RH and Temperature outputs.

A large supply voltage (2.4 V – 5.5 V) capability, coupled with robustness towards external stresses and adjustable power consumption enablesw the sensor to meet varying customer needs.

These CO2 sensors use Sensirion’s PASens technology, which is based on the photoacoustic sensing principle. The photoacoustic sensing principle allows extreme miniaturisation of the CO2 sensor without compromising sensor performance because the sensor sensitivity is independent of the optical cavity size.

The reduced size and the smaller number of integrated components result in a highly price-efficient BOM structure.


The SCD4x sensors come in two model variants, the SCD40 with a specified accuracy of ± (50 ppm + 5% of reading) for CO2 levels 400 – 2’000 ppm and the SCD41 with a specified accuracy of ± (40 ppm + 5% of reading) for CO2 levels 400 ppm – 5’000 ppm. The humidity sensing range is 0 %RH – 100 %RH with typical accuracy of 6% over 15 °C – 35 °C, 20 %RH – 65 %RH and 9% over -10 °C – 60 °C, 0 %RH – 100 %RH. Temperature measurement range is - 10°C – 60°C with a typical accuracy of 0.8°C over 15 °C – 35 °C and 1.5°C over -10 °C – 60 °C.

The sensors are supported by the SEK-SCD41 evaluation kit which has been designed for easy and cost-efficient evaluation of the sensors. The kit contains a SCD41 mounted on a development board with a JST connector and through-hole pins.

An adapter cable (JST-Ethernet) connects to the SEK-SensorBridge for easy evaluation of the sensor via the SEK-ControlCenter viewer software. The kit also contains a 4-pin jumper wire cable that enables fast prototyping, e.g. through integration into existing evaluation platforms (like Arduino, Raspberry Pi, etc.).

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