This model is designed to measure temperature, relative humidity and dew-point temperature by internal sensor, moreover one additional external temperature probe Pt1000/E can be connected. Internal sensors are located under the grid on the front of the unit and are protected with Teflon foil. Foil permits water vapour but prevents water from permeating the liquid state. The device also measures the temperature from an external probe and the difference between this temperature and the dew point temperature. If the surface temperature of the material is measured by an external probe, the risk of condensation of water vapor on the surface to be measured can be determined immediately. The device alone is suitable for measuring in places where there is no rapid change in temperature or relative humidity, and there is no condensation of water vapours. If water vapour condensation occurs inside the datalogger, then the resulting water will remain there and may damage its electronics. The device is placed directly in the measured space, while the installation needs to ensure sufficient level of GSM signal at the installation location. As the internal battery creates a parasitic heat during the charging period, the measurement accuracy may be affected by up to 1 º C. The calibration of this instrument in the laboratory is recommended with the open bottom part of the battery box, to allow airflow from the back of the electronics. When airflow in the range 0.5 – 1 m/s, read the value after approx. 4 hours. The closed device reaches a difference of approximately 2% when inserted in the humidity chamber, then dramatically slows down. Precise reading takes many times longer time than with the open rear lid. The maximum length of each probe lead should not exceed 15 m. It is recommended to use shielded cables. To maintain the IP rating, the unused probe connector should be provided with a supplied closing cap.