A wireless hygrometer is an instrument used to measure the relative humidity of an air sample. Most hygrometers reach this measurement by comparing the ambient temperature with the temperature of condensation in the air sample and then plotting that information on a graph or using an equation to find the relative humidity. In meteorological science, hygrometers are used to measure atmospheric humidity. The wireless hygrometer is also used in any situation when humidity must be closely controlled to protect the items being stored in a space, for example the paintings in a museum or cigars in a humidor.
The simplest form of wireless hygrometer is the psychrometer. This device uses a pair of thermometers to take readings that are then used to figure out the relative humidity. One of the thermometers takes a dry-bulb temperature, meaning that the thermometer bulb is kept dry to measure the ambient temperature. The bulb of the other thermometer is kept damp. The wet-bulb temperature is the lowest temperature that can be reached through the evaporation of water.
Measurements from the two thermometers are recorded. The difference between the two measurements can be used to figure out the amount of humidity in the air. This is done using a psychrometric chart. The psychometric chart is a graph that plots variables such as bulb temps, relative humidity, and the humidity ratio. The humidity ratio is the proportional mass of moisture to dry air. Some hygrometers are able to directly plot the measurements onto a psychrometric chart for later review.
Even with a wireless hygrometer, it is difficult to guarantee an accurate measurement of relative humidity. Since relative humidity is the humidity as measured in relation to the ambient temperature of the air sample, small changes in air temperature can translate to large changes in relative humidity, even if the absolute humidity has not changed. Hygrometers are sensitive instruments that must be calibrated regularly to ensure the most accurate readings possible.
The wireless hygrometer can be found at many stages of the industrial manufacturing process. A warehouse might use a hygrometer to make sure that its raw materials are kept at an optimal humidity. The spaces where people work might be monitored by a hygrometer to make sure that the air conditioning systems are working efficiently. At the finishing stage, a hygrometer would be used when paint is being applied. Paint is very sensitive to humidity and dries best in a controlled environment.