The thermometer is an instrument used to measure temperatures. Depending on the type of thermometer, it can measure body temperature, water, air and many other things.
The thermometer is used in the clinical, chemical part and even in gardening. Air and water expand and contract due to the temperature that exists.
When Galileo understood the relationship between these two elements, it was the moment when he decided to create something that would help him decipher the temperature, being in 1592 when he invented a rudimentary thermometer that would lay the foundations for the creation of more advanced thermometers.
This first thermometer did not have a scale, it only used water to show changes in temperature and how it rose or fell.
It was the physicist Santorio who put a scale on a thermometer for the first time. But because they did not properly know how the water expands, these thermometers were very imprecise.
In the year 1714, the physicist and engineer Gabriel Fahrenheit created the first thermometer that used mercury instead of water, as it expanded and contracted faster.
In addition, the expansion of mercury is more predictable so it can be measured more easily, at the same time it published its scale that today is called the Fahrenheit scale to measure temperature.
This scale was very famous in the century, but it would be the Swedish Anders Celsius who in 1742, and despite the fact that it was rejected at first, would introduce the scale most used today. It set 0 ° C as the freezing point of water and 100 ° C as the boiling point.
Thermometer parts
There are different types of thermometers that are used in different industries, each adapted to the place where it will be placed, but they all have the same function: to measure temperature.
We can highlight the thermometer known as clinical, which continues to work based on mercury despite the many technological alternatives that exist in the market.
The reason this is one of the most famous is because mercury goes from solidified to liquid quickly, consequently expanding more quickly and offering a much more accurate measurement.
Bulb
The bulb is the base of mercury thermometers. It is located at the bottom and is cylindrical or spherical depending on the artifact. The functionality of the bulb is to store the mercury and it is usually stainless steel, but it can be glass as well.
When it comes into contact with the place to be measured and the temperature rises, the mercury leaves the bulb and when the temperature falls, the mercury falls and is deposited again inside the bulb.
The size of this affects its sensitivity to changes in temperature, the finer it is, the more sensitive it will be, since the mercury will come into contact with cold or heat more quickly.
Capillary
The capillary or stem is the tube through which the mercury flows. It is located inside the glass body of the thermometer and is connected to the bulb.
It is the route that allows the mercury to travel until it reaches the temperature at which the target is being measured and back to the bulb.
The size of the stem also affects the measurement, since if it was long it would take longer for the mercury to fully expand, giving a wider temperature range.
Body
The body is the glass tube that covers the stem. It is elongated and triangular in shape but the edges are softened, giving them a rounded look for better handling. It usually measures 20 to 30 cm.
It is for this part that mercury thermometers have been given so many negative replies, since if it is ingested in considerable quantities it can be toxic.
Due to the fact that the glass body is considered delicate and very fragile, it is imperative to take care of it from falls or extremely strong grip, because it could break and leak the liquid.
However, glass is used because it filters the temperature in a good way. One of the sides of this is a magnifying glass, which makes reading easier.
Expansion compartment
The expansion compartment is the space found above the stem, where gas and air are deposited while the mercury rises and where the mercury will be located in case it is exceeded.
When the mercury reaches the compartment, it means that the thermometer cannot expand further and reach higher degrees of temperature.
Scale
The scale comprises the markings on the body of the thermometer and indicates the temperature level. Depending on the thermometer it can be either ° F or ° C.
Valve
The shrink valve is the connector between the bulb and the stem. Because it is narrower than the stem, this valve is the cause of the mercury going down slowly; giving the person the necessary time to read the temperature reached.
Features
Clinical thermometer
The use given to the thermometer depends very much on the reason for which it was manufactured. Each thermometer has been specially created to make its measurement in a certain place, but absolutely all have the same and exclusive function: to measure the temperature of something. The 4 most important are:
-Clinical thermometer: includes the traditional and electronic thermometer. Its function is to take the temperature in humans (sometimes animals). It is used in the mouth, armpit, or rectum.
-Gas thermometer: they are used more than everything in the industry to measure the temperature of confined gases.
-Pyrometer: type of thermometer whose function is to measure extreme temperatures, it can measure temperatures higher than 600 ° C. It uses infrared technology and is used mainly in the metallurgical industries.
-Resistance thermometer: its function is to receive the variations in electrical resistance and convert them into temperature variations.
References
- Radford, T (2003) A brief history of thermometers. Extracted from theguardian.com.
- Pearce, J (2002) A brief history of the clinical thermometer. Published in Quarterly Journal of Medicine, Volume 95, Issue 4.
- British Broadcasting Corporation (2011) Types of thermometers. Extracted from bbc.co.uk.
- (2016) Thermometer, use and functions. Extracted from instrumentsdelaboratorio.org.
- Markings, S. Different Parts of a Mercury Thermometer. Extracted from oureverydaylife.com.
- Camilleri, P. Extracted from staff.um.edu.mt.
- Bellis, M. The history behind the thermometer. Extracted from theinventors.org.