Thermometer Main Parts and Functions

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Egbert Haynes

The thermometer It 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 and even gardening areas. 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 not knowing properly how the water expands, these thermometers were very inaccurate.

In 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. This 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 the temperature..

We can highlight the thermometer known as clinical, which continues to work based on mercury despite the multiple technological alternatives that exist in the market.

The reason why this is one of the most famous is because mercury goes from being solidified to liquid quickly, consequently it expands more quickly and offers 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 made of stainless steel, but it can be made of 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 it 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 make its way 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 were 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. 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 the gas and air are deposited while the mercury rises and the place 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 have ° F or ° C.

Valve

The shrink valve is the connector between the bulb and the stem. Being narrower than the stem, this valve causes the mercury to go 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). Used in the mouth, armpit, or rectum.

-Gas thermometer- Used mostly in 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 electrical resistance variations and convert them into temperature variations.

References

  1. Radford, T (2003) A brief history of thermometers. Extracted from theguardian.com.
  2. Pearce, J (2002) A brief history of the clinical thermometer. Published in Quarterly Journal of Medicine, Volume 95, Issue 4.
  3. British Broadcasting Corporation (2011) Types of thermometers. Extracted from bbc.co.uk.
  4. (2016) Thermometer, use and functions. Extracted from instrumentsdelaboratorio.org.
  5. Markings, S. Different Parts of a Mercury Thermometer. Extracted from oureverydaylife.com.
  6. Camilleri, P. Extracted from staff.um.edu.mt.
  7. Bellis, M. The history behind the thermometer. Extracted from theinventors.org.

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