Tiny CO2 sensor works at high concentrations

Author: EIS Release Date: Nov 17, 2020

Sensirion has introduced a sensor for measuring high concentrations of CO2, based on a thermal conductivity technique.


Called STC31, it is aimed at ‘controlled atmosphere’ transportation, where CO2, humidity and temperature are monitored and set to preserve the freshness of fruits and vegetables.

“Exact conditions depend a lot on the exact commodity, with typically a low temperature, high humidity and CO2 concentration somewhere between 1% and 20%,” according to the company.

Sensiron-co2-sensor-STC31Called STC31, the sensor works by measuring the thermal conductivity of the gas in its environment (diagram left) and delivers both CO2 concentration and temperature over its I2C interface.

Built in is an option to compensate for the humidity – relative humidity has to be communicated to the STC31, and with this information the sensor will output a compensated concentration value. When no humidity value is delivered, it assumes a relative humidity of 0%.

Power consumption averages to 15µW at one measurement per minute, suiting it to battery power.

“By relying on the thermal conductivity technology, the sensor offers low power consumption, even compared to low-power optical sensors,” said the company.

Accuracy is 0.5vol% and ±3% of measured value, and the response time is <1s.

Construction is CMOS and the chip includes sensor, signal processing and digital calibration.

The package is 3 x 3.5 x 1mm.