The Bacharach Sling Psychrometer from Paul N. Gardner USA accurately determines percent relative humidity without the necessity of consulting complex tables. It contains a slide rule calculator that correlates wet- and dry-bulb thermometer indications for direct reading of relative humidity. 

The Sling Psychrometer consists of two thermometers that are turned by vigorously swinging the handle and exposing the thermometers to rapid air movement. These two thermometers are called dry-bulb and wet-bulb. The bulb of one thermometer is placed in direct contact with the room air to measure dry-bulb air temperature. The bulb of the other thermometer is covered with a silk or muslin sleeve that is kept moist to record the wet bulb temperature. Evaporation cools the wet-bulb more than the dry-bulb, and the humidity is obtained as a function of change in temperature. The atmospheric humidity is determined by calculations, steam tables, or using a psychrometric chart.

Features include:

• Designed for portability (7.5" long x 1" diameter)
• Slide rule construction quickly converts temperature to relative humidity
• Built-in water reservoir holds sufficient water for several hours of testing
• Thin bulb design gives fast thermal response
• Thermometers constructed of shock-resistant glass; stems have deep-etched numerals and 1° scale divisions for easy reading
• Accurate to within ±5% R.H

Applications include laboratories and manufacturing facilities.

More information on this product can be found at here.

More information on Paul Gardner can be found at www.gardco.com.