In life, we often find some very routine items in the self-work, many people are full of curiosity about this, how do they work? For example, we are all very interested in the electric kettle, generally after the water boiling automatically cut off the power supply, so what is the principle of it? Today, small Mori with everyone to see it!
First, according to the principle of thermal expansion and cold contraction of objects. Thermal expansion and cold contraction are common characteristics of objects, but the degree of thermal expansion and cold contraction of different objects is not the same. A piece of copper is used to make a contact. Because copper is sensitive to thermal expansion and cold contraction, when the temperature does not reach the set value, the copper sheet is curved, and its contacts are closed and connected. When the water is heated to the set temperature, the heat of the water will be transmitted to the copper sheet in the thermostat and the copper sheet on top of it will be straightened by the heat and spring the contact open into a power off state. When the temperature drops, the copper sheet returns to its original state so that the contact is switched on and heated. The two sides of the double gold sheet are conductors of different substances. Due to the different degrees of expansion and contraction under the changing temperature, the double gold sheet is bent, and the set contact or switch is touched, so that the set circuit begins to work. This is more direct and timely, you can accurately sense the water temperature.
Secondly, the water in the kettle is burned dry power is automatic temperature control circuit. In the circuit series temperature sensor, the boiling point of water is one hundred degrees, when the water is boiled, the temperature will exceed one hundred degrees, then the temperature sensor will disconnect the circuit. Simple temperature sensors are bimetallic sheets commonly used in electric appliances such as irons and water heaters. There are many kinds of temperature sensors. There are semiconductor temperature sensors. The structure is simple, safe and reliable.