A hygrometer is an instrument used to measure the amount of water vapor in air, in soil, or in confined spaces. Humidity measurement instruments usually rely on measurements of some other quantities such as temperature, pressure, mass, a mechanical or electrical change in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use temperature of condensation (called the dew point), or changes in electrical capacitance or resistance to measure humidity differences. A crude hygrometer was invented by the Italian Renaissance polymath Leonardo da Vinci in 1480. Major leaps forward came during the 1600s; Francesco Folli invented a more practical version of the device, while Robert Hooke impro