The most accurate way to measure Relative Humidity (RH%)!
Two 5½ red spirit-filled thermometers are attached to the metal back for whirling. To obtain an RH%, simply wet the wick of the wet-bulb thermometer, whirl the psychrometer, and view both thermometer readings. Then, using the chart provided, determine the RH% (the optional slide rule makes this easier). Purchase this device at www.qasupplies.com