CO₂ Sensor - STC31 (Qwiic)

The Sparkfun STC31 is a highly accurate CO₂ sensor capable of sensing concentrations up to 100%. It offers two measurement ranges: 0 to 25 vol% and 0 to 100 vol%, with a repeatability of 0.2 vol% and stability of 0.025 vol% / °C. The accuracy of measurements varies depending on the range: 0.5 vol% + 3% measured value; 1 vol% + 3% measured value.

The STC31 features a Sensirion SHTC3 humidity and temperature sensor. This allows the STC31 to deliver humidity-compensated measurements along with improved temperature compensation. It can also compensate for atmospheric pressure, making it a versatile tool for various environments.

Part of Sensirion’s STC3x sensor family, the STC31 is designed for high-volume applications. It uses a revolutionized thermal conductivity measurement principle, ensuring superior repeatability and long-term stability. This makes it an ideal choice for applications where reliability is a priority.

The STC31 is built on Sensirion’s patented CMOSens® sensor technology. This technology integrates the sensor element, signal processing, and digital calibration on a small CMOS chip. This makes it an excellent choice for high-quality mass production and demanding, cost-sensitive OEM applications.

The I²C address of the STC31 can be configured using the split-pad jumpers on the back of the board. The SHTC3’s I²C address is non-configurable. If you wish to connect multiple sensors to the same bus, a Qwiic Mux will be needed.

This sensor board includes a power LED, a pair of Qwiic connectors, I²C breakout pads, and pull-up resistors. The LED and pull-ups can be disabled by cutting the I2C jumpers on the back of the board. All these features make the STC31 a user-friendly and flexible sensor for various applications.

Sparkfun provides an Arduino library with example sketches for the Arduino IDE to help users get started quickly. The SparkFun Qwiic Connect System is an ecosystem of I²C sensors, actuators, shields, and cables that make prototyping faster and less prone to error. All Qwiic-enabled boards use a common 1mm pitch, 4-pin JST connector, reducing the amount of required PCB space and ensuring error-free connections.

The STC31 is a product of SparkX, Sparkfun's platform for rapidly producing cutting-edge technology. While these products are tested, they come with no guarantees and live technical support is not available.

Features:

• Sensirion STC31 CO₂ Sensor with thermal conductivity sensor providing calibrated gas concentration and temperature output
• Measurement ranges: 0 to 25 vol%; 0 to 100 vol%
• Accuracy: 0.5 vol% + 3% measured value; 1 vol% + 3% measured value
• Repeatability: 0.2 vol%
• Temperature measurement range: -20 °C to +85 °C
• Concentration and temperature resolution: 16-bit
• Start-up time: 14 ms
• I²C address (configurable): 0x29 (default), 0x2A, 0x2B, 0x2C
• Supply Voltage: 2.7V_Min, 3.3V_Typ, 5.5V_Max
• Note: Qwiic bus operates at 3.3V_Max
• Sensirion SHTC3 Humidity and Temperature Sensor
• Typical accuracy: ±2 %RH and ±0.2 °C
• Specified humidity range (extended): 0 to 100 %RH
• Specified temperature range: -40 °C to +125 °C
• I²C address (non-configurable): 0x70
• Supply Voltage: 1.62V_Min, 3.3V_Typ, 3.6V_Max
• Note: Qwiic bus operates at 3.3V_Max
• Dual Qwiic connectors
• Power LED (configurable)
• I²C pull-ups (configurable)

Documents:

• STC31 Datasheet
• STC Field Calibration Guide
• STC Design-In Guide
• Schematic
• Eagle Files
• Arduino Library
• Hardware Repo