Showing posts with label sling hygrometer. Show all posts
Showing posts with label sling hygrometer. Show all posts

Measurement of Atmospheric Moisture

Wet & Dry Bulb Hygrometer


  • This is an instrument equipped with two thermometers, side by side.
  • The bulb of one of the thermometers is covered with a muslin wick dipping into water.
  • The water is absorbed up the muslin and evaporates, cooling.
  • The difference between the wet and dry bulb temperatures is called the wet bulb depression.
  • If the air is fully saturated (100% relative humidity) the water cannot evaporate, so both the wet and dry bulb temperatures are the same.
                                                            

Hair Hygrometer


  • These devices use a human or animal hair under tension.
  • The hair is hygroscopic (tending toward retaining moisture); its length changes with humidity, and the length change may be magnified by a mechanism and indicated on a dial or scale.
  • The traditional folk art device known as a weather house works on this principle. Whale bone and other materials may be used in place of hair.
  • This instrument uses strands of human or horse hair with the oils removed attached to levers that magnify a small change in hair length.