Paul N. Gardner USA introduced the compact, portable Sling Psychrometer, an easy way to measure relative humidity levels quickly and accurately. The compact, portable Bacharach Sling Psychrometer accurately determines percent relative humidity without the necessity of consulting complex tables. There is no need to wet the wick each time a reading is taken; the Sling Psychrometer contains a slide rule calculator which correlates wet and dry bulb thermometer indications for direct reading of re...