In general, a thermometer is a type of measuring instrument used to determine the temperature of a body and an object. In a sense, it is used to see how hot or how cold the body or the object is.
Apart from being used to measure the temperature of objects, some thermometers are used to measure room temperature, fuel, and as an indicator of heat in certain tools. The thermometer that is often encountered by the public is a digital thermometer as a medical device.
In a thermometer, there are generally lines that are equipped with numbers as a scale and the main component is a thermometric substance. This thermometric substance will react when it receives hot or cold temperatures so that measurement results can be obtained.
This substance is usually in the form of a liquid, though some are not liquid, depending on the type of thermometer. There are several types of thermometers that have their respective functions. In order not to make the wrong choice when using it, let’s get to know the types of thermometers and their functions.
1. Mercury Thermometer
A mercury thermometer is a thermometer that uses mercury as a filler. When the hot temperature is absorbed by the mercury, the mercury will expand and begin to rise to a point that indicates the temperature of the object.
However, when the temperature drops, the position of the mercury remains in place. This is because there is a contraction that prevents the mercury from falling. To lower it to its original position, you need to turn it upside down firmly. After returning to its original place, it can be used to measure the temperature of another object.
This thermometer is a thermometer that is often found to determine body temperature during fever. But over time, this thermometer has been replaced by a digital thermometer that is easier to see the measurement results.
However, this thermometer is commonly used for laboratory practical purposes. Because it contains mercury which is one of the dangerous substances, this thermometer is not highly recommended for use. It will be very dangerous if broken.
2. Alcohol Thermometer
This thermometer is similar to a mercury thermometer, except that the filler in this thermometer is alcohol. Alcohols are more sensitive to temperature changes so that their volume can be clearly seen when reading the measurement results. In addition, this thermometer is safer than the mercury thermometer. This thermometer is also called the minimum thermometer because it can measure low temperatures.
3. Mechanical Bimetal Thermometer
A mechanical bimetal thermometer is a thermometer that takes advantage of the properties of two metals with different coefficients of expansion. As the name implies, bi means two and metal means metal.
When there is a change in temperature, the two metals will expand and begin to warp. That’s when the needle in the thermometer moves in response to the curvature of the two metals and shows the measured temperature.
The working principle of this thermometer is that when a hot temperature occurs, the bimetal strip will bend towards the metal with a high expansion coefficient or vice versa. This bimetal thermometer is used to measure the temperature of thermostats, ovens, grills, and other industrial tools as an indicator of a heat threshold.
4. Digital Thermometer
A digital thermometer is a thermometer that is generally used to measure a person’s body temperature by tucking it in the armpit or in the mouth. This thermometer is made of plastic and is shaped like stationery. This thermometer uses an electronic sensor to detect body temperature.
This thermometer is very sensitive to temperature changes and very easy to use. After tucking it in the armpit or mouth, it will pause for a moment before the display on the digital thermometer shows the temperature and is stable at that number.
Its simple use makes this thermometer widely used for health purposes, laboratory purposes, and cooking purposes.
5. Infrared Thermometer
An infrared thermometer is a thermometer for measuring the temperature of a certain object or body part without touching the object because it uses infrared or laser light.
The way it works is by detecting thermal radiation emitted by objects with infrared light. This type of thermometer has been common recently. It’s used to measure the temperature of a person before they’re entering the crowd to meet health protocols during the COVID-19 pandemic.
6. Probe Thermometer
The probe thermometer is a thermometer that has a tapered sensor tip that is connected by a long cable. The pointed tip is what serves to detect heat. This thermometer is generally used in the health, laboratory, retail, and food fields by dipping the tip of the thermometer to the object. The cable is long enough to allow flexibility in its use.
7. Wall Thermometer
As the name suggests, this thermometer is hung on the wall of the room. Wall thermometer works to measure room temperature which is usually made of wood equipped with capillary pipes filled with mercury or alcohol.
As with mercury and alcohol thermometers, the liquid in this capillary tube expands when it finds a hot temperature. Wall thermometers are also expressed in Celsius and Fahrenheit units.
8. Resistance Thermometer
A resistance thermometer is a thermometer that is used to measure extreme temperatures that range between -250oC and 700oC. The way this thermometer works is by recording changes in the resistance of the liquid flowing through a platinum wire wrapped around a glass or ceramic material.
Platinum is used because of its good accuracy and wide temperature range. However, if there is no platinum, it can be replaced with copper or nickel. This thermometer is generally used in the fields of automation and process control.
9. Maximum-Minimum Thermometer (Six Bellani)
A maximum-minimum thermometer is a thermometer that is used to measure the maximum temperature and minimum temperature of a place within a certain period of time. This thermometer was invented by James Six Bellani, so this thermometer is also called the Six Bellani thermometer.
The working principle is that when the temperature rises, the mercury in the ball will expand and force the narrow part so that it enters the scaled capillary tube.
The mercury tip on the right shows the highest air temperature. Then when the air temperature drops, the mercury column will remain in place because it is held back by a narrow pipe. To make it return to its original position, it is necessary to swing it firmly.
10. Resistor Thermometer
A resistor thermometer is a thermometer that takes advantage of changes in resistance (resistor) in a conductor due to changes in temperature. This thermometer is made of electronic components with high accuracy. This tool is commonly found in industry which is used to measure the temperature of gas fuel pipes. The price of this thermometer is quite expensive so that it is used only on an industrial scale.
11. Humidity Thermometer
A humidity thermometer is a thermometer that measures the humidity in the room. This thermometer is equipped with an electronic sensor that can measure room temperature at a certain time. So the temperature value on this thermometer varies according to changes in room humidity.
This thermometer can be found in a laboratory room or in a home as a home accessory because it is sometimes also equipped with a clock.
Those are the types of thermometers. Each thermometer has its own advantages and disadvantages. After knowing the types of thermometers above, make sure you don’t choose the wrong thermometer again when you want to measure the temperature of an object.