Sensirion STCC4 CO2 Sensor: Tiny Footprint, Massive Potential

Sensirion STCC4 - A miniature CO₂ sensor for indoor air quality

Measuring just 3 x 4 x 1,2 mm, the STCC4 is a miniature CO₂ sensor specifically optimised for environments where changes are relatively small and gradual, typical of stationary indoor applications. Rather than using traditional optical methods, it measures the thermal conductivity of the surrounding air to calculate CO₂ concentration.

How the Sensirion STCC4 works

1. A MEMS heater is activated for approximately 250 ms.
2. Heat from this element is transferred to the surroundings via thermal conduction, convection, and radiation.
3. Heat transfer is a dynamic process; once the heater kicks in, conduction becomes the dominant factor. Consequently, the temperature changes measured by the MEMS sensor depend on the environment's thermal conductivity.
4. Any shift in that conductivity is interpreted as a change in CO₂ concentration.

Because the STCC4 is non-selective, it cannot distinguish exactly which gas caused a change in thermal conductivity. For this reason, it is intended for indoor environments where human breath is the primary driver of CO₂ fluctuations.

Thermal conductivity is primarily affected by temperature, though relative humidity (RH) and atmospheric pressure also play smaller roles. To keep readings accurate, the STCC4-D-R3 features a dedicated I²C interface designed for Sensirion’s SHT4x humidity and temperature sensors. When an SHT4x is connected, the system automatically uses its data to compensate for temperature and RH.

Operation without an SHT4x is made possible via recording temperature and RH values from an external sensor using the set_rht_compensation command. External pressure data can also be set via the set_pressure_compensation command.

To ensure long-term stability, the sensor utilizes an Automatic Self-Calibration (ASC) algorithm. This is always active and assumes the STCC4 will be exposed to fresh air (roughly 400 ppm CO₂) at least once a week.

Operating modes of the Sensirion STCC4 sensor

• Continuous measurement mode: period T_m = 1 s, I_AVG = 950 uA typ.
• Single shot measurement mode: recommended T_m = 5 – 600 s, I_AVG = 100 uA typ. for T_m = 10 s.
• Idle mode: I_AVG = 55 uA typ.
• Sleep mode: I_AVG = 1uA max.

Both the STCC4-D-R3 sensor and the SEK-STCC4 evaluation kit are now in stock and so ready to ship for your next project.

Our portfolio also includes a wide range of other gas sensors from Sensirion, either available immediately or sourced upon request under favourable conditions.

Interested in more information about Sensirion products or need technical advice on choosing the right product? Have any other questions or requests? Reach out, and we’ll be happy to assist!