California based company, Integrated Device Technology (IDT) has recently announced their new HS300x family of MEMS high-performance relative humidity (RH) and temperature sensors of dimension 3.0 × 2.41 × 0.8 mm DFN-style 6-pin LGA. Currently, there are four devices in this family—the HS3001, HS3002, HS3003, and HS3004. They are all the same from the view of functionality but differ slightly in terms of the accuracy of their relative humidity and temperature measurements.
The highlighted feature of this new lineup is that they do not require any user calibration. HS300x family of ICs has calibration and compensation logic integrated into the devices. These ICs output their fully corrected data using standard I2C protocols making the measured data from the sensors is rather easy.
As a side note, Relative humidity (RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. As the entire output consists of only four bytes of data, calculating the corresponding relative humidity in percent and temperature in degrees Celsius is very easy.
Although the HS300x sensors operate as slave devices on the I2C bus (supporting clock frequencies from 100 kHz to 400 kHz), only one HS300x IC can be connected directly to a single I2C bus. To connect multiple sensors to a single I2C bus, an I2C multiplexer/switch has to be used. It would have been easier if IDT had dedicated the unused pin as an optional I2C address input bit, which would allow two HS300x devices to be connected to a single I2C bus.