He laboratory thermometer is an instrument used to measure the exact temperature of substances. Being able to measure the temperature through a thermometer, it can be controlled. This instrument is manufactured to calculate both low and high temperatures.
There are materials that respond to different temperatures, such as some metals, eg mercury (liquid substance).
For this reason, the thermometer is designed with a tube, usually glass, that has mercury inside.
On the outside, he has written down the temperatures he can measure. In addition, at one end a metal tip protrudes, which will be the one that will come into contact with what is to be measured.
When the metal tip comes in contact with a substance, the mercury begins to dilate when feeling a different temperature.
This causes it to rise along the tube, passing the numerical scale until it stops at that figure that will indicate the temperature in which the substance is.
This is the description of a modern laboratory thermometer. In the past, the tube had an opening at one end, which was submerged in the liquid (water with alcohol) to be measured.
Inside the tube was a sphere that rose depending on the temperature of the liquid.
History of laboratory thermometer
The laboratory thermometer was born from the aspiration of measuring temperatures in general. The first idea of an instrument to measure temperature is attributed to Galileo Galilei , who in 1593 created a way of measuring the temperature change in water. This is what is now known as a thermoscope.
In 1612, the Italian Santorio Santorio, added a numerical scale to the idea of Galileo Galilei. This can be considered as a first approach to the clinical thermometer.
However, Ferdinand II, Duke of Tuscany, modified the design of Galilei and Santorio in 1654. His modifications were to close both ends of the tube and change the water by alcohol to determine the temperature. Despite its reforms, this was not a fully functional thermometer.
The person who transformed the thermometer into the modern model was Daniel Gabriel Fahrenheit. In 1714, this man decided to change the liquid used by mercury. In this way, it became possible to measure lower and higher temperatures.
Measuring scales
There are different types of scales in which a thermometer can mark the temperature, whether this is laboratory or not. The scales are as follows:
- Celsius or centigrade (ºC), created by Anders Celsius, Swedish astronomer. In 1742, he proposed a scale of 0 ° C to 100 ° C, 0 representing the lowest temperature and 100 the highest.
- Fahrenheit (° F), named by its creator, Daniel Fahrenheit, in 1724. This scale is 180 divisions, with 32 ° F the coldest point and 212 ° F the hottest point. Fahrenheit created this scale using as reference the heat of the human body, measured at 98.6 F.
- Kelvin (K), like the previous ones, this one also bears the name of its inventor, Lord Kelvin (William Thomson). This scale was invented in 1848 and was based on the Celsius scale.
Maintenance
It can be thought that a thermometer does not need any maintenance, since this works with the change of temperature.
However, like many other measuring instruments, the thermometer must be calibrated to avoid errors in its operation.
There are some thermometers that serve to calibrate. Calibration can sometimes be done at home but, if not possible, it is necessary to contact an expert.
Types
Most thermometers work in the same way. However, even if their objective is the same (ie measuring the temperature to be able to control it) there are different types of laboratory thermometers and some of them are the following:
Liquid thermometer in glass
This type is the most common. It is a sealed glass tube that contains mercury or red alcohol inside, since the danger of contact with mercury has been studied.
These two types of liquids react with the change in temperature, either contracting if it is low or expanding if it is high.
Usually, this type of thermometer is represented on a Celsius scale, but can also be found on the Fahrenheit scale.
Thermometer with bimetallic foil
The bimetallic sheet thermometer is formed, as its name implies, with two metal sheets that are connected to each other, but that react differently. These blades curl when coming into contact with a change in temperature.
That movement is perceived by a spiral, which translates through a needle the level of the temperature that is being measured.
Digital thermometer
The digital thermometers are made with a microchip that receives the information that the electronic circuits capture over the temperature. The microchip receives and analyzes the information and then displays the numerical results on the screen.
In addition, an advantageous feature of this model is that it does not have any type of component that could be harmful to life.
These thermometers, being part of the technological advances, can do more than just measure the temperature. The more functions you have, the higher your cost.
Infrared Thermometer
The infrared thermometer, also known as infrared pyrometer or non-contact thermometer, differs from other types of thermometers by measuring the thermal radiation and not the temperature as such.
Thanks to its built-in infrared technology, it is able to measure the temperature of what you want, without touching or being near.
Therefore, this thermometer is functional to measure those substances or objects with which it is not advisable to come into contact.
Resistance Thermometer
The temperature with this type of thermometer is measured through an electric resistance and a platinum wire or other kind of pure material incorporated, which respond to changes in temperature.
It is considered that even though the levels it marks, it is a bit slow.
References
- Bellis, M. (April 17, 2017). The history of the thermometer. Retrieved on September 14, 2017, from thoughtco.com.
- Who invented the thermometer. Retrieved on September 14, 2017, from brannan.co.uk.
- Laboratory thermometers: what is the best choice for your application? Retrieved on September 14, 2017, from globalgilson.com.
- Different types of thermometer and their uses. Retrieved on September 14, 2017, from atp-instrumentation.co.uk.
- Laboratory thermometer. Retrieved on September 14, 2017, from miniphysics.com.
- Liquid in glass laboratory thermometer. Retrieved on September 14, 2017, from brannan.co.uk.
- Resistance thermometer. (July 21, 2017). Retrieved on September 14, 2017, from en.wikipedia.org.
- Thermometer. (September 13, 2017). Retrieved on September 14, 2017, from en.wikipedia.org.