A thermometer is a functional instrument mainly used to gauge body or atmospheric temperature. By controlling temperatures of certain applications, thermometers can help regulate different chemical reactions. In addition, it is also utilized to record melting points and boiling points.
There are many types of thermometers. Among the most basic types that you will find in the market are the Liquid-in-glass thermometers, ashcroft bimetal thermometers, electrical thermometers, and gas thermometers.
Liquid-in-glass thermometers
Liquid-in-glass thermometers work on the premise that liquids expand when subjected to heat. These thermometers have glass tubes with small bulb at the bottom that functions as the liquid reservoir. The thermometric liquid used for these thermometers are either mercury or alcohol. You can use this to measure body temperature. As the thermometer gets into contact with the body, the liquid expands and goes up until the gauge reaches the point where the temperature is equal to the body temperature.
Mercury is common used to act as the thermometric liquid because it is a good conductor of heat and it doesn’t stick to the interior of the glass thermometer. It is bright in color and can easily be read when measuring a temperature. This type of thermometer is common used in households, chemical laboratories, and medical facilities.
Bi metal thermometers
Ashcroft Bimetal thermometers consist of two strips of different metals, usually brass and Invar. These strips are joined together; as they are exposed to heat, the two metals undergo expanding and contracting processes at different rates. They are commonly used to monitor and control temperature in refrigerators.
Electrical Thermometers
Electrical thermometers are further classified in two forms: the resistance thermometer and the thermocouple thermometer. The first form of thermometer works on the premise that the resistance of metals is directly proportional to the increase in temperature. The second form works using two different metals; one stays in ice and the other goes to the object whose temperature needs to be measured or recorded. Thermocouple converts heat to electricity and produces a voltage that varies in temperature.
Gas Thermometers
In this type of thermometers, the thermometric substances being utilized can be nitrogen, hydrogen, or helium. Gas thermometers are categorized in two: constant volume and constant pressure thermometers. This technology works on the principle that gases expand when subjected to heat; and by measuring the expansion or gas, the temperature can then be recorded.
Different scales of temperature
There are basically four scales used in recording temperature: the Celsius scale, Fahrenheit scale, Reaumur scale, and the Absolute scale of temperature. Here is a summary of the freezing point and boiling point of each scale:
- Celsium or Centigrade scale – The freezing point of water is 0° while the boiling point is 100°
- Fahrenheit Scale – The freezing point of water is 32° and the boiling point is 212°
- Reaumur Scale – The freezing point of water is 0° while the boiling point is 80°
- Absolute scale – The freezing point of water is 273° while the boiling point is 373°
