Hygrometer
A hygrometer is an instrument used for measuring the moisture content in the environmental air, or humidity. Most measurement devices usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed. From calculations based on physical principles, or especially by calibration with a reference standard, these measured quantities can lead to a measurement of humidity. Modern electronic devices use temperature of condensation, or changes in electrical capacitance or resistance to measure humidity changes.
Hygrometers give a dial indication of humidity changes, and they are very inexpensive devices but their accuracy is very limited.
Hair tension hygrometers These devices use a human or animal hair under tension. The length of the hair changes with humidity and the length change may be magnified by a mechanism and/or indicated on a dial or scale. The traditional folk art device known as a "weather house" works on this principle.
Hair tension hygrometers These devices use a human or animal hair under tension. The length of the hair changes with humidity and the length change may be magnified by a mechanism and/or indicated on a dial or scale. The traditional folk art device known as a "weather house" works on this principle.