The Elcometer 116 & Bacharach 116C Whirling Sling Hygrometers (part numbers G116A and G116C) determine the dewpoint and relative humidity of the air at any given time using the classic wet and dry bulb principle, also known as the psychrometric method. Knowing these climatic conditions before coating matters because applying paint or a protective coating in the wrong humidity, or when the surface is at or near dewpoint, leads to moisture on the substrate and premature coating failure.

The Elcometer 116 carries two spirit-filled thermometers, one with a wetted wick. Whirling or slinging the unit draws air across both bulbs, and the difference between the wet and dry bulb readings is converted to relative humidity and dewpoint using the supplied tables or slide rule. Both bulbs of the Elcometer 116 read across a measuring range of -5°C to 50°C (23°F to 122°F), with a typical RH accuracy of around 5% RH when correct technique and standard psychrometric tables are used. The unit weighs 300g and is compact at 17 x 22mm.

Operation of the Elcometer 116 is fully manual, with no batteries, power supply, or electronics, which makes it dependable on remote sites and in hazardous or explosive atmospheres where electronic instruments are unsuitable. The thermometers are mercury-free. The Elcometer 116 conforms to ASTM E337-B, BS 2842 and ISO 8502-4, the standards used for climatic condition monitoring in surface preparation and coating inspection. Supplied by BAMR, South Africa's authorised distributor.