Reference

Library

• Arduino Library: Download and install the SCD4X Library. (About how to install the library?)
• Raspberry Pi Python Library: Download and install the SCD41 CO2 Sensor python library.

Communication Protocol Description

The sensor uses I2C communication. The I2C address is 0x62.

API Description

/**
   * @fn enablePeriodMeasure
   * @brief set periodic measurement mode
   * @param mode - periodic measurement mode:
   * @n       SCD4X_START_PERIODIC_MEASURE : start periodic measurement, signal update interval is 5 seconds.
   * @n       SCD4X_STOP_PERIODIC_MEASURE : stop periodic measurement command
   * @n       SCD4X_START_LOW_POWER_MEASURE :  start low power periodic measurement, signal update interval is approximately 30 seconds.
   * @return None
   * @note The measurement mode must be disabled when configuring the sensor; after giving the stop_periodic_measurement command, the sensor needs to wait 500ms before responding to other commands.
   */
  void enablePeriodMeasure(uint16_t mode);

  /**
   * @fn readMeasurement
   * @brief Read the measured data
   * @param data - sSensorMeasurement_t, the values measured by the sensor, including CO2 concentration (ppm), temperature (℃) and humidity (RH)
   * @return None
   * @note CO2 measurement range: 0~40000 ppm; temperature measurement range: -10~60 ℃; humidity measurement range: 0~100 %RH.
   */
  void readMeasurement(sSensorMeasurement_t * data);

  /**
   * @fn getDataReadyStatus
   * @brief get data ready status
   * @return data ready status:
   * @n        true : data ready
   * @n        false : data not ready
   */
  bool getDataReadyStatus(void);

Principle

CO2 is a key factor for indoor air quality as high levels compromise human’s cognitive performance and well-being.

This Gravity: SCD41 CO2 sensor is based on the SCD41 miniature CO2 sensor from Sensirion. SCD41 builds on the photoacoustic NDIR sensing principle and Sensirion’s patented PAsens® and CMOSens® technology to offer high accuracy at an unmatched price and smallest form factor. On-chip signal compensation is realized with the built-in temperature and humidity sensor, while temperature and humidity data outputs are also available.

SCD41 sensor detects the amount of energy that is absorbed by CO2 molecules. When pulsing the infra-red emitter, CO2 molecules absorb infrared light periodically. This causes additional molecular vibration resulting in a pressure wave inside the measurement chamber. The higher the CO2 concentration, the more light is absorbed, and thus the greater the amplitude of this acoustic wave becomes. A microphone inside the gas chamber measures this, from which the CO2 concentration can then be calculated.

Click to learn more about PAsens® technology.

Click to learn more about NDIR sensor.

Click to learn more about What types of NDIR sensors exist and how do they work?

Click to learn more about Design-in guide