Sensirion CO2 Sensors
Precise Monitoring in Any Environment
Introduction to CO2 Sensors
Carbon dioxide (CO2) sensors are crucial for developing smart devices that enhance living comfort, health, and energy efficiency, finding applications in HVAC, consumer electronics, and medical devices. Leveraging the latest advancements in measurement principles, Sensirion offers solutions for various application scenarios. Sensirion provides support throughout the entire development process, from initial concept to product launch, including prototyping, design support, and online testing during mass production. Their sensor portfolio also covers environmental parameters such as humidity, temperature, volatile organic compounds (VOC), particulate matter (PM), formaldehyde, and nitrogen oxides (NOx).
CO2 Sensing Measurement Principles
Non-Dispersive Infrared (NDIR)
CO2 molecules absorb specific wavelengths of infrared (IR) light. NDIR CO2 sensors pass IR light through a measurement cell and use a detector to measure how much light passes through (i.e., how much was absorbed by CO2 molecules). By comparing this to a reference light intensity, the CO2 concentration can be determined. NDIR CO2 sensors come in two types: single-channel and dual-channel. The reference measurement channel in dual-channel NDIR enhances long-term stability.
[Diagram Description: An NDIR sensor setup showing an infrared light source emitting light, passing through a measurement cell containing gas molecules (including CO2 molecules), an infrared filter, and finally reaching a detector (PCB). The principle is that CO2 molecules absorb specific IR wavelengths, reducing the light intensity detected.]
Photoacoustic NDIR (PA)
PA technology uses a pulsed IR light source that emits wavelengths absorbed by CO2. The absorption of light by CO2 molecules causes additional molecular vibration, increasing the pressure within the measurement cell. Since the light source is pulsed, this pressure increase occurs periodically, generating sound waves. The amplitude of these sound waves, measured by a microphone, allows for the calculation of CO2 concentration.
[Diagram Description: A PA NDIR sensor setup featuring a pulsed infrared emitter, a measurement cell with CO2 molecules, a protective membrane, and a microphone. The absorption of pulsed IR light by CO2 molecules creates pressure waves detected by the microphone.]
Thermal Conductivity (TC)
TC is based on the inherent thermal conductivity of all gases. If the composition of the gas in an environment is known, subtle changes in gas concentration can be detected. This measurement principle involves heating the air within a measurement chamber and using a temperature sensor to detect heat transfer.
[Diagram Description: A TC sensor setup showing a heating element, a measurement chamber containing gas, and a temperature sensor. The sensor measures how heat is transferred from the heating element to the gas, which is dependent on the gas's composition and concentration.]
SCD30
The SCD30 is Sensirion's most advanced NDIR CO2, relative humidity, and temperature sensor module. Its dual-channel optical measurement principle enables best-in-class CO2 measurement accuracy and excellent long-term stability. The ultra-thin package size and UART, I2C, and PWM interfaces facilitate easy integration and space-saving designs. The SCD30 complies with California Title 24, EN50543, RESET®, and WELL Building Standard® for relevant building codes and IAQ standards.
Product Features
- NDIR sensing technology
- Dual-channel measurement principle
- Integrated CO2, relative humidity, and temperature sensor module
- Sensirion CMOSens® IR detector
- UART, I2C, and PWM interfaces
- Thinnest NDIR sensor module
Product Advantages
- High accuracy, selective CO2 measurement
- Excellent long-term stability through reference channel compensation
- Three outputs with on-chip temperature and humidity compensation
- Cost-effective
- Flexible interfaces and readout
- Streamlined design, ideal for wall-mounted devices
Applications
- Commercial and residential HVAC systems
- Demand-controlled ventilation (DCV)
- Energy recovery ventilation (ERV)
- Wall-mounted thermostats
- Duct CO2 sensors
SEK-SCD30 Evaluation Kit
- 1 × SCD30 on SEK adapter PCB with RJ45 connector and pin header (2.54 mm pitch)
- 1 × RJ45 adapter cable (1 meter)
- Requires SensorBridge (purchased separately)
SCD4x
The SCD4x utilizes the photoacoustic NDIR sensing principle and Sensirion's PASens® and CMOSens® patented technologies, combining small size with high accuracy for excellent cost-effectiveness. The SCD4x offers two distinct models: the SCD40 for cost-sensitive applications and the SCD41 for applications requiring compliance with California Title 24, RESET®, and WELL Building Standard® or needing single-shot measurements.
Product Features
- Photoacoustic NDIR sensing technology
- Compact size: 10.1 × 10.1 × 6.5 mm³
- Full encapsulation
- Lifespan over 10 years
- Robust design: dust, water, and mechanical resistance
- SMD (Surface-Mount Device) package, tape and reel packaging
- On-chip compensation and self-calibration
- Wide voltage range: 2.4–5.5 V
- Multiple operation and low-power modes
- Digital I2C interface
Product Advantages
- High accuracy, selective CO2 measurement
- Space-saving integration
- Suitable for applications with over 10 years of lifespan
- Resistant to dust, water, and mechanical stress
- Enables highly automated, cost-effective on-board assembly
- Calibrated and linearized sensor output with long-term drift compensation (ASC) for various applications
- Flexible trade-off between power consumption and performance
- Simple design and interface
Applications
- Commercial or residential HVAC systems
- Wall-mounted thermostats
- Air purifiers
- Indoor air quality monitors
SEK-SCD41 Evaluation Kit
- 1 × SCD41 development board
- 1 × Adapter cable
- 1 × Jumper kit
- Requires SensorBridge (purchased separately)
STCC4
The STCC4 is Sensirion's new generation CO2 sensor based on thermal conductivity principles. It is the world's smallest direct CO2 sensor, designed for seamless integration into compact electronic devices, setting a new standard for multifunctionality and adaptability. The STCC4 opens up new opportunities for CO2 monitoring applications currently constrained by size and cost. The sensor is scheduled for official launch in Q2 2025.
Product Features
- Thermal conductivity technology
- Ultra-compact size: 4 × 3 × 1.2 mm³
- Low power consumption: 950 µA
- Minimal component count
- SMD (Surface-Mount Device) package, tape and reel packaging
- Digital I2C interface
Product Advantages
- Direct CO2 concentration measurement
- Space-saving design
- Supports low-power applications
- High reliability
- Enables direct design integration
- Simple sensor communication
Applications
- Smart speakers
- Smart thermostats
- Air conditioners
- Indoor air quality monitors
STC31-C
The STC31-C is a gas concentration sensor based on thermal conductivity principles. It is chip-scale, capable of precisely measuring high CO2 concentrations, and offers excellent repeatability and long-term stability, making it an ideal choice for applications requiring high reliability. The STC31-C introduces a new low cross-sensitivity measurement mode with intelligent humidity and oxygen compensation, enabling new applications such as measuring exhaled CO2.
Applications
- Controlled atmosphere storage systems
- Exhaled CO2 measurement
- CO2 measurement in medical ventilators
- CO2 leak detection
Product Features
- Thermal conductivity technology
- Ultra-low power
- Compact size: 4 × 3 × 1 mm³
- Minimal component count
- Fast response
- Voltage range: 2.7–5.5 V
- Automatic Calibration (ASC)
- Low-power mode
- SMD (Surface-Mount Device) package, tape and reel packaging
- Intelligent humidity and oxygen compensation
- Digital I2C interface
Product Advantages
- Ultra-low power consumption
- Adaptable to various devices
- High reliability
- Enables measurement of exhaled CO2
- Flexible for battery-powered and wired applications
- Autonomous offset compensation
- Suitable for battery-powered applications
- Direct design integration
- On-chip signal compensation
- Simple sensor communication
SEK-STC31-C Evaluation Kit
- 1 × STC31-C and 1 × SHT40 on FPCB
- 1 × RJ45 adapter cable (1 meter)
- Requires SensorBridge (purchased separately)
Product Comparison
| Parameter | SCD30 | SCD40 | SCD41 | STCC4 | STC31-C |
|---|---|---|---|---|---|
| Measurement Principle | NDIR | Photoacoustic NDIR | Photoacoustic NDIR | Thermal Conductivity | Thermal Conductivity |
| CO2 Accuracy | ± (30 ppm + 3 %) | ± (50 ppm + 5% of reading) @ 400–2,000 ppm | ± (50 ppm + 2.5% of reading) @ 400–1,000 ppm; ± (50 ppm + 3% of reading) @ 1,001–2,000 ppm; ± (40 ppm + 5% of reading) @ 2,001–5,000 ppm | ± (100 ppm + 10%) | ± (0.2 … 2.0 vol %) |
| CO2 Output Range | 400–10,000 ppm | 0–40,000 ppm | 400–5,000 ppm | 0–100 vol % | |
| Min Sampling Rate | 2 s | 5 s | 1 s | 0.066 s | |
| Response Time (τ63%) | 20 s | 60 s | 20 s | 0.5 s | |
| Size | 35 × 23 × 7 mm³ | 10.1 × 10.1 × 6.5 mm³ | 4 × 3 × 1.2 mm³ | 4 × 3 × 1 mm³ | |
| Assembly | Through-hole | SMD | SMD | SMD | |
| Interface | I2C, PWM, Modbus | I2C | I2C | I2C | |
| Lifespan | 15 years | > 10 years | > 10 years | > 10 years | |
| Voltage Range | 3.3–5.5 V | 2.4–5.5 V | 2.7–5.5 V | 2.7–5.5 V | |
| Average Current (Periodic Mode) | 19 mA | 3.3 V = 15 mA, 5V = 11 mA | 950 µA @ 1 Hz | 150 µA @ 1 Hz | |
| Operating Temperature | 0 to 50 °C | –10 to +60 °C | 10 to 40 °C | –10 to +50 °C | |
| Operating Humidity | 0–95% RH | 0–95% RH | 20–80% RH | 0–95 % RH | |
| Low Power Mode | Variable sampling interval | Periodic low power | Periodic low power | Single shot | Single shot |
| IAQ Standards Compliance | EN50543, RESET, WELL, California Title 24 | EN50543, RESET, WELL, California Title 24 | Single shot | Single shot | Not for IAQ applications |
