The SHT40, SHT41, and SHT45 have identical pinouts.
- VIN - This is the power pin. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V microcontroller like Arduino, use 5V.
- 3V - This is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like.
- GND - common ground for power and logic.
The default I2C address is 0x44.
- SCL - I2C clock pin, connect to your microcontroller I2C clock line. This pin is level shifted so you can use 3-5V logic, and there's a 10K pullup on this pin.
- SDA - I2C data pin, connect to your microcontroller I2C data line. This pin is level shifted so you can use 3-5V logic, and there's a 10K pullup on this pin.
- STEMMA QT - These connectors allow you to connectors to dev boards with STEMMA QT connectors or to other things with various associated accessories.
The I2C address is 0x44 and cannot be changed (a manufacturer limitation). If you must monitor multiple sensors with one microcontroller, look at the PCA9546 4-channel or TCA9548A 8-channel multiplexer.