Whirling Hygrometer – Overview

The whirling hygrometer also known as a sling psychrometer is made out of two thermometers mounted on a frame which rotates around a handle, so it can be whirled in the air by hand. One thermometer is covered with a tight-fitting muslin sock which is kept wet by distilled water. This type of thermometer is known as the wet-bulb thermometer. The other is the dry-bulb thermometer as it is exposed to the atmosphere directly. In air with less than 100 per cent relative humidity, the wet bulb will display a lower temperature than the dry bulb and is known as wet-bulb depression. A special chart is used to convert the wet-bulb depression to relative humidity or the relative humidity can be determined by correlating the readings with those on a simple slide rule, which is supplied with each instrument.

Whirling Hygrometer – Features

• Made in accordance with BS2842
• Housed in a yellow plastic case with folding handle
• Available in Red Spirit
• Supplied with Hygrometric tables, spare wick and instructions
• No electronics and therefore great for us in mines

Optional: Case