Adafruit Sensirion SHT40 Temperature & Humidity Sensor - STEMMA QT / Qwiic

Sensirion Temperature/Humidity sensors are some of the finest & highest-accuracy devices you can get. And finally, Adafruit have some that have a true I2C interface for easy reading. The SHT40 sensor is the fourth generation (started at the SHT10 and worked its way up to the top!). The SHT40 has an excellent ±1.8% typical relative humidity accuracy from 25 to 75% and ±0.2 °C typical accuracy from 0 to 75 °C.

Unlike some earlier SHT sensors, this sensor has a true I2C interface for easy interfacing with only two wires (plus power and ground!). Thanks to the voltage regulator and level shifting circuitry Adafruit have included on the breakout It is also is 3V or 5V compliant, so you can power and communicate with it using any microcontroller or microcomputer.

Such a lovely chip - so they spun up a breakout board with the SHT4x and some supporting circuitry such as pullup resistors and capacitors. To make things even easier, Adafruit have included SparkFun Qwiic compatible STEMMA QT connectors for the I2C bus so you don't even need to solder! QT Cable is not included, but Adafruit have a variety in the shop. 

If you prefer working on a breadboard, each order comes with one fully assembled and tested PCB breakout and a small piece of header. You'll need to solder the header onto the PCB, but it's fairly easy and takes only a few minutes even for a beginner. 

Arduino have written both Arduino and CircuitPython/Python library code for this chip, so you can use it with just about any microcontroller or single-board computer like Raspberry Pi.

Technical Specifications

• Relative humidity accuracy: up to ±1.8 %RH
• Temperature accuracy: up to ±0.2 °C
• Breakout supply voltage: 3.3 to 5V
• Average bare sensor current: 0.4 μA (at meas. rate 1 Hz)
• Idle bare sensor current: 80 nA
• I2C fast mode plus, CRC checksum
• Operating range: 0…100 %RH, -40…125 °C
• Fully functional in condensing environment
• Variable power heater
• NIST traceability for sensor
• JEDEC JESD47 qualification for sensor
• Mature technology from global market leader Sensirion
• I2C address 0x44