Leonardo da Vinci designed an early hygrometer to indicate changes in atmospheric humidity.
His concept used a material whose weight or condition would change as it absorbed moisture from the air. By comparing that material with a dry reference, an observer could detect variations in humidity. The design formed part of Leonardo’s broader investigations into air, water, weather, and measurement.
A hygrometer measures moisture in the atmosphere, while a barometer measures air pressure and an anemometer measures wind speed. These instruments are often grouped together because all are used in weather observation, but they measure different physical properties.
Leonardo’s device was an early scientific instrument rather than a modern electronic humidity sensor. Its importance lies in the attempt to turn an invisible atmospheric condition into a measurable quantity.