The Elcometer 309 Delta T Hygrometer provides a simple and fast measurement of these two critical characteristics.
- Delta T (TΔ): 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): This is the amount of water vapour taken up by air. Expressed as a percentage, RH is dependent on the air temperature. Typical maximum RH values specified by paint manufacturers are between 75% and 85%.