Description:

To optimize accuracy of temperature and humidity readings, the SHT21 sensor is placed at the tip of the board, isolating it from heat producing circuitry. Two of the sensor has four pins are ground and +5V; the other two are clock and data pins that make up the 2-wire serial interface. The board is 5V tolerant and designed to operate directly off the supply voltage.

The sensor can be placed in soil to measure moisture and temperature, which makes it ideal for using it in a garden or greenhouse. The humidity sensor is also especially useful in building remote weather stations.

Specifications:

Energy consumption: 80 uW (at 12 bit, 3V, 1 measurement/s)

Relative Humidity operating range: 0-100% RH

Relative Humidity resolution of 0.03%

Relative Humidity Response Time of 8 sec (tau 63%)

Temperature operating range: -40 to +125°C

Temperature resolution of 0.01 C

4 pins: +5V, GND, Clock (SCL), Data (SDA)

Bidirectional communication over a single pin on I2C protocol

Board is 5V tolerant, allowing sensor to run from a 5V supply on I/O pins

Package includes:

4 x HTU21D Temperature & Humidity Sensor

The humidity and temperature sensor board that carries a digital SHT21 humidity and temperature sensor from Sensirion.
Si7021 GY-21 Module Industrial High Precision Humidity Sensor I2C IIC Interface Module For Arduino Low Power CMOS IC Module
It has a 4-pin interface that can communicate directly with the analog pins
It can be used as a hardware- and software-compatible drop-in upgrade for existing RH/temperature sensors in 3x3 mm DFN-6 packages, featuring precision sensing over a wider range and lower power consumption.
The Si7021 offers an accurate, low-power, factory-calibrated digital solution ideal for measuring humidity, dew-point, and temperature, in applications ranging from HVAC/R and asset tracking to industrial and consumer platforms.