This hygrometer is finished in antiqued copper, uses a 4.25 inch diameter dial face and is great for monitoring greenhouses, sunrooms or problem areas. Included is an outdoor swivel arm bracket for mounting at just the right angle, as well as an indoor mounting pin. Hygrometers measure the moisture content of the air to determine the relative humidity. Our mechanical hygrometers take advantage of a time-tested method in which a synthetic fiber expands as it absorbs moisture from the air. This expansion, in turn, moves the metal coil to which it is bonded. As the coil twists, the pointer moves up the scale. As the fiber dries, the coil contracts and the pointer reverses direction. Relative humidity ranging from 45 to 70 percent is generally considered to be comfortable. Use in combination with a humidifier or de-humidifier to maximize your comfort
