The Wet and Dry Bulb Thermometer is also a hygrometer, which is simply an instrument used to measure the relative humidity of the atmosphere. It consists of two thermometers, one with a bulb that is kept dry and one that is kept moist. The relative humidity is calculated from the difference in readings of the thermometers when water evaporates from the wet bulb, decreasing its temperature. Readings are graduated in Celsius -20° to +50° (in 1°C increments) and Fahrenheit 0° to +120° (in 2°F increments). Includes humidity table in both C and F as well. 

• Graduated in Celsius -20° to +50° (1°C) and Fahrenheit 0° to +120° (2°F)
• Includes humidity table in C and F
• Easy-to-read, high accuracy
• Sturdy construction, plastic body
• Dimensions 10″ x 3″ x 0.5″