Thermometer is based on the principle that a liquid expands on heating and contracts on cooling.
These liquid thermometers are based on the principal of thermal expansion. When a substance gets hotter, it expands to a greater volume. Nearly all substances exhibit this behavior of thermal expansion. It is the basis of the design and operation of thermometers.The operating principle of a thermometer is quite simple. A known measure of liquid (mercury, alcohol, or a hydrocarbon-based fluid) is vacuum-sealed in a glass tube. The liquid expands or contracts when air is heated or cooled.In a mercury thermometer, a glass tube is filled with mercury and a standard temperature scale is marked on the tube. With changes in temperature, the mercury expands and contracts, and the temperature can be read from the scale. Mercury thermometers can be used to determine body, liquid, and vapor temperature.
Digital thermometers contain a small computing mechanism and a resistor. A change in temperature causes the sensor to notice a change in resistance. The computer converts the difference in resistance into a difference in temperature and offers a digital readout in degrees. thermometer measures temperature through a glass tube sealed with mercury that expands or contracts as the temperature rises or falls. ... As temperatures rise, the mercury-filled bulb expands into the capillary tube. Its rate of expansion is calibrated on the glass scale.
A thermometer is a device used for measuring temperature. ... A thermometer is an instrument that measures temperature. It can measure the temperature of a solid such as food, a liquid such as water, or a gas such as air. The three most common units of measurement for temperature are Celsius, Fahrenheit, and kelvin.
- Digital thermometers. Digital thermometers are regarded as the fastest and most accurate type of thermometer. ...
- Electronic ear thermometers. ...
- Forehead thermometers. ...
- Plastic strip thermometers. ...
- Pacifier thermometer. ...
- Glass and mercury thermometers.
A thermometer for measuring body temperature that has a constriction in the tube above the bulb preventing movement of the column of liquid downward once it has reached its maximum temperature so that it continues to indicate the maximum temperature until the liquid is shaken back down into the bulb.