Soil temperature measurements on the CHMI observatories were performed using mercury soil thermometers under the standardized grassy soil in depths of 5, 10, 20, 50 and 100 cm. In Doksany, also measurements under bare soil and in depths of 2 and 30 cm are being held. Step by step, mercury thermometers were replaced by way more accurate electronic measurement, applying Pt100 sensors. After its setting, some serious problems arised, and it was necessary to solve them. Sensors are arranged into special casing (see picture), which, next to protecting function, also permits routine exchange of sensors within calibration, without affecting the soil profile. In 2003, the staff of the Doksany observatory carried out replacement of all soil sensors on all professional observatories of CHMI, and in 2004, on 24 voluntary observation stations. Replacement will be step by step carried out on the rest of the observatory stations. If the sensors are installed directly in the soil, without casing, then, according to DWD, the data will be presentable after two years of measuring. In Doksany, STP01 sensor is also used for measuring of the change in soil temperature in depths of 2, 5, 10 and 20 cm (using thermocouples), compared with soil temperature in depth of 50 cm (Pt100 sensor), also, measuring under selected crops is performed.