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BlueDot SGP40+SHT40 Indoor Air Quality VOC Sensor


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Monitor indoor air quality and measure the VOC Index with the sensors SGP40 and SHT40 from Sensirion.
• Sensor outputs are the VOC Index, temperature, and relative humidity.
• VOC Index is a value between 1 and 500.
• Measure temperatures from -20°C to 55°C.
• Measure humidity from 0% to 100%.
• I²C communication.
• Full tutorial with everything you need.

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The SGP40 is Sensirion’s new digital gas sensor for integration into air treatment devices and air quality monitors. The sensor provides a digital raw signal that is sensitive to most volatile organic compound (VOC) gases typically present in indoor environments. The signal is proportional to the logarithm of the resistance of the sensing material.

The raw signal from the SGP40 is processed by Sensirion’s Gas Index Algorithm, which provides a VOC Index as a robust measure of indoor air quality. For improved accuracy, the Gas Index Algorithm reads the temperature and relative humidity measurements from the second sensor on this board, the SHT40 from Sensirion. This way, the Gas Index Algorithm adapts to the environmental conditions the sensor is exposed to.

The VOC Index is a value ranging from 1 to 500. The value 100 refers to the average indoor gas composition over the past 24 hours. While values between 100 and 500 indicate a deterioration, values between 1 and 100 indicate an improvement in the air quality.

The temperature and humidity sensor SHT40 also contains a temperature-controlled micro hotplate, which can be used for self-decontamination. This is particularly useful for creep compensation caused by extended exposure to high humidity or environments with solvents present.

Here are the board’s main features:

  • High Repeatability. Typical repeatability of ±5 VOC Index points at 25°C and 50% relative humidity.
  • Temperature and Humidity Compensation. The measurements from the SHT40 are used by the Gas Index Algorithm to improve the accuracy of the VOC Index.
  • Wide Range Supply Voltage. The sensor operates from 1.8 V and 5.5 V at VCC, dispensing the need for voltage regulation.
  • I²C Communication. Using the I²C communication protocol you need no more than two wires to transfer data from and to your board.