# HECA 2 - relative humidity air conditioning device for PM sensors
HECA 2 is more compact version of [HECA](https://easyeda.com/nettigo/Nettigo-Air-Monitor-Heating-Element-Control) with different enclosure.
In this design we used precise temperature and humidity sensor from Swiss company Sensirion: SHT30 (or SHT31/SHT35) connected via I²C. This sensor is equipped with programmable ALERT output....
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