Elcometer 309 [G309----1] Digital Delta T Hygrometer

The Elcometer 309 digital Delta T Hygrometer provides a simple and fast measurement of Delta T temperature and relative humidity. Delta T (TΔ) is the difference between the surface temperature (Ts) and the dewpoint temperature (Td). When TΔ is less than 3ºC (5ºF) painting should not occur. Relative Humidity (RH) - expressed as a percentage, RH is the ratio of the amount of water vapour actually held by the air compared to the maximum amount of water vapour the air could hold at a given temperature.  Typical maximum RH values specified by paint manufacturers are between 75% and 85%.