Thermometer principle

The principle of mercury thermometer is that it expands when heated and contracts when cooled.

At present, there are generally three kinds of thermometers used in the market: mercury thermometer, infrared thermometer and electronic thermometer. The principle of mercury thermometer is that mercury expands when it is hot and contracts when it is cold; mercury moves up when it is hot and moves down when it is cold. The infrared thermometer measures the temperature according to the amount of infrared radiation from the measured object. The higher the temperature of an object, the more infrared rays it radiates. The electronic thermometer is designed based on the principle that thermistor senses temperature.

The earliest thermometer was invented by Italian scientist Galileo (1564 ~ 1642) in 1593. His first thermometer was a glass tube with an opening at one end and a glass bulb the size of a walnut at the other. When in use, the glass bulb is heated first, and then the glass tube is inserted into water. With the change of temperature, the water surface in the glass tube will move up and down, and the temperature change and temperature level can be judged according to the movement amount.

Temperature measurement skills

1. When measuring the surface temperature of luminous objects such as aluminum and stainless steel, the reflection of the surface will affect the reading of infrared thermometer. Before reading the temperature, a rubber strip can be placed on the metal surface, and after the temperature is balanced, the temperature in rubber strip area can be measured.

2. If the infrared thermometer can walk back and forth from the kitchen to the cold storage area and still provide accurate temperature measurement, it will take some time to reach the temperature balance in the new environment before the measurement. It is best to put the thermometer in a place where it is often used.

3. Use infrared thermometer to read the internal temperature of liquid food, such as soup or sauce, which must be stirred before measuring the surface temperature. Keep the thermometer away from the steam to avoid polluting the lens and causing incorrect reading.

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