Calibrated humidity and temperature sensors Sensirion SHT21, SHT25 and STS21 excel by very small dimensions. Thanks to their miniature size and a very low power consumption, you can use them even in small portable devices.
Sensors SHT21, SHT25 and STS21 with I2C digital output belong to the SHT product line, with the CMOSens technology of swiss company Sensirion. SHT21 and SHT25 measure relative humdity and temperature, STS21 measure only temperature. With a new CMOSens chip, reworked capacitive type humidity sensor and the improved band-gap temperature sensor they feature excellent properties. They have very similar and in some aspects even better properties than SHT1x and SHT7x sensors. Also these sensors belong to high quality CMOS sensors, which contain all elements of the measuring chain on one chip: humidity and temperature sensor, precise supply, low noise linear amplifier, AD converter and interface. Inspite of very compact dimensions also SHT21 and 25 sensors remain resolution of 12 bits for relative humidity and 14 bits for temperature. Temperature sensor STS21 has also a 14 bit resolution and a user can choose by a command the resolution of 14, 13, 12 or 11 bits.
I2C interface enables a very simple communication with a host microcontroller, in a Hold/ No Hold Master mode. Defaultly sensors have the same I2C adress set from production. Upon request it is possible to provide sensors with various adresses from producer. STS21 is fully compatible with SHT2x but it has a different I2C address. This enables to use sensor STS21 in applications where humidity measurment is optional and enables to use the same hardware.
New sensors Sensirion will take you only 3x3mm on PCB! - [Link]