Bacharach 0012-7043 Sling Psychrometer, Celsius scale, -5 to 50 °C

Bacharach 0012-7043 Sling Psychrometer Only Comes in Blue
The uniquely compact Bacharach Sling Psychrometer accurately determines percent relative humidity without the necessity of consulting complex tables. There is no need to wet the wick each time a reading is taken; the Sling Psychrometer contains a slide rule calculator which correlates wet and dry bulb thermometer indications for direct reading of relative humidity. When not in use, the thermometer case telescopes into the handle for protection.