1.1.3. Temperature, humidity and VOCs Sensor (THV)

1.1.3.1. Introduction

The ESDK-THV board provides two sensors that report a total of three metrics including

• Temperature

• Relative humidity

• Volatile Organic Compounds (VOCs)

1.1.3.2. Schematic diagram

1.1.3.3. Theory of operation

The ESDK-THV utilises a Sensirion SHT31 to provide temperature and relative humidity measurements accurate to 2% RH and 0.2°C. A Sensirion SGP40 provides a processed sensor output with an “VOC Index” unit from 0-500, with an ethanol equivalent measuring range of 0-1000ppm. Further reading about the Sensirion “VOC Index” measurement can be found here.

To help reduce thermal influence from the PCB, the SHT31 is mounted on a tab routed out of the board with only small traces connecting 3.3V/GND/I2C.

Both sensors appear on the I2C bus with separate addresses of 0x41 for the SHT31 and 0x59 for the SGP40.

1.1.3.4. Board layout