Temperature monitoring systems: The hygrometer evolution.

Hygrometers are instruments used to measure the amount of water in the air, which have been around since the mid 1700s. The ways to actually do the measuring have evolved since then so that today in addition to the hair hygrometer, thermohygrographs and electronic hygrometers are used. Very inexpensive hygrometers are used as barometers in meteorology to monitor and predict weather changes, however this instruments are not accurate enough for museums and art galleries. Museums and art galleries use very accurate hygrometers to monitor the amount of moisture in the indoor environment over a long period of time. Most museums monitor these conditions 24 hours a day since the wrong moisture level can damage valuable paintings and other works of art. They tend to use the more accurate psychrometers and electronic hygrometers. Temperature, expressed in degrees Celsius (