The environmental conditions during pre-treatment and application of a coating system are major factors affecting the long-term performance of coatings on steel structures. The PosiTector dew point meter measures and records climatic parameters including relative humidity, air temperature, surface temperature, dew point temperature and the difference between surface and dew point temperatures. The instrument is suitable for surface preparation as required by ISO 8502-4 and ASTM D3276. The instrument has a backlit display; Smart Trend indicators to identify rising, falling or stable readings; a graph mode to chart all five parameters for quick analysis; and memory capacity to store up to 2,500 datasets in 100 batches. The instrument converts to accept various optional K-type probes including magnetic and handheld surface temperature probes.