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A hygrometer is an instrument which measures the humidity of air or some other gas: that is, how much of it is water vapor. [1] Humidity measurement instruments usually rely on measurements of some other quantities, such as temperature, pressure, mass, and mechanical or electrical changes in a substance as moisture is absorbed.
A thermo-hygrograph. A thermo-hygrograph or hygrothermograph is a chart recorder that measures and records both temperature and humidity (or dew point).Similar devices that record only one parameter are a thermograph for temperature and hygrograph for humidity.
Although the principles of psychrometry apply to any physical system consisting of gas-vapor mixtures, the most common system of interest is the mixture of water vapor and air, because of its application in heating, ventilation, and air-conditioning and meteorology.
Capacitance hygrometers are not affected by most volatile chemicals and can be much smaller than other alternative sensors. They do not require cleaning, but are less accurate than dew point hygrometers (+/- 0.015 a w). They should have regular calibration checks and can be affected by residual water in the polymer membrane (hysteresis).
Thermistors principle: relation between temperature and electrical resistance of ceramics or polymers, range: from about 0.01 to 2,000 kelvins (−273.14 to 1,700 °C) Thermocouples principle: relation between temperature and voltage of metal junctions ( Seebeck effect ), range: from about −200 °C to +1350 °C
A simple soil moisture sensor for gardeners. Soil moisture sensors measure the volumetric water content in soil. [1] Since the direct gravimetric measurement of free soil moisture requires removing, drying, and weighing of a sample, soil moisture sensors measure the volumetric water content indirectly by using some other property of the soil, such as electrical resistance, dielectric constant ...
Moisture analysis covers a variety of methods for measuring the moisture content in solids, liquids, or gases.For example, moisture (usually measured as a percentage) is a common specification in commercial food production. [1]
Inexpensive dial-type hygrometers make use of this principle using a coiled strip. Deliquescence is the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution.