What Purpose Does the Hygrometer Serve?

Humidity is a measure of the amount of water vapor in the air.

A hygrometer is an instrument used to measure humidity or the amount of ambient water vapor in the air. The first hygrometers used human hair, since hair expands with increasing humidity, and a hygrometer made with human or animal hair actually will work reasonably well. Typically, however, meteorologists rely on more sophisticated instruments that use change in electrical resistance or capacitance to make sensitive measurements. Hygrometers serve a number of different purposes in different industries.

Meteorology

For weather forecasters, measuring humidity is an important part of trying to predict tomorrow's weather. Relative humidity can help assess the chance of rain, snow or fog. Humidity is one of the important parameters meteorologists track (together with other variables like temperature, pressure and wind speed) when making a weather forecast; typically they rely on hygrometers to measure humidity.

Museums

Museum collections store and display delicate items, many of which are centuries old; if these artifacts are improperly cared for, they may deteriorate rapidly. Consequently, museums need to maintain an environment that will help prevent decay in paintings and other fragile items. Humidity is a key consideration because excess humidity can promote mold growth. If the humidity fluctuates frequently, wooden items can shrink or warp, paint can chip from canvases, or undesirable chemical reactions can take place. Museums often monitor humidity with the aid of a hygrometer.

Greenhouses

Greenhouses help create controlled conditions for plant growth, since they make it possible to regulate light, humidity and temperature. Measuring humidity inside the greenhouse with a hygrometer--and altering the humidity as needed--can help ensure optimum plant growth.

Humidors and Other Uses

Humidors are cabinets or rooms whose contents are kept at constant humidity and temperature; they're typically used to store tobacco and cigars. Most humidors are equipped with a hygrometer to monitor the humidity, since it's important to keep it as stable as possible. Hygrometers also find application in various processes in industry, especially processes that involve painting or coating metal surfaces, since humidity can impact quality or delay drying and curing.

Considerations

Even with a good hygrometer, measuring humidity isn't always easy. While hygrometers are accurate enough for most everyday purposes, they must be frequently recalibrated, and the inaccuracies associated with humidity measurement are sometimes a challenge for meteorologists.

References

• Smithsonian Institute: Catalog of Meteorological Instruments
• "USA Today": How Humidity is Measured
• World Meteorological Organization: Measurement of Humidity
• Foundation of the American Institute for Conservation: Managing the Museum Environment
• Humidor Hygrometer.net: Purchasing a Humidor Hygrometer