Wireless outdoor thermometers work using thermoresistors to measure temperature. The thermoresistor varies the amount of electricity it allows through the circuit based on the temperature. This information is converted to a digital value and transmitted through a system similar to a baby monitor over distances up to 100 feet. By placing the receiver on his bedside table, the owner reads the outside temperature while still in bed.Continue Reading
Some wireless units have the capability of adding more sensors. With the additional sensors, the owner is able to determine the temperature in locations such as the basement, garage or other sensitive area at the base unit. Armed with the information, he knows if he needs to increase the heat to prevent pipes from freezing, wear warmer clothing for the day or take precautions to prevent frost damage to sensitive plants.
Older indoor-outdoor thermometers worked with an outdoor bulb that connected to a glass gauge in the home through a thin tube. Expanding alcohol or mercury in the bulb caused the level to rise in the gauge inside the window. However, installation required a small hole through which the bulb and tube passed to the outside. The connection limited the distance from the home for the thermometer. Often the units gave false readings because the proximity of the bulb to the house kept it warmer than the actual outside temperature.Learn more about Outdoor