This pocket size sling psychrometer is a self contained instrument to measure humidity by comparing wet and dry bulb thermometers. All calculations are made with the sliding calculator on the instrument case. It is available in both Celsius and Fahrenheit models with mercury or spirit filled thermometers.

To operate the sling psychrometer, withdraw thermometers halfway out of case and fill the well with water, so the wick is moistened. Holding the case handle, swing the thermometer around for approximately two minutes. Read the wet and dry bulb temperatures, then reinsert the thermometer slide back into the case. The slide and case form a slide rule for calculating RH. Instructions are enclosed in the instrument. Dimensions: 8-1/4"H x 1-1/4"W x 5/8"L.