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A dive into the world of thermometers

Glass, digital or infrared technology? Which model is right for you: the fastest or the most reliable? What are the pros and cons of each type of thermometer?

The glass thermometer: Precise, but fragile


Advantages: they are among the most reliable and accurate thermometers . 

Curiosity: Similar to the old mercury thermometer, banned since April 2009, the modern glass thermometer contains an alloy of less polluting and non-toxic metals inside. In this way, it reduces the environmental impact! 


Disadvantages: It is falling out of favor because it is made of glass, takes a long time to measure and is difficult to read for some people. Keep in mind that if you travel frequently, the thermometer is made of glass and can break easily In addition, gallium, one of the substances present in this thermometer, is difficult to remove if spilled on a surface. Leave a mark.



Digital thermometers: Reliability and good price

Advantages: The digital thermometers are characterized by a screen that displays the temperature. The digital thermometers are among the best choices you can make because they combine reliability at affordable cost In this group, we find two possible formats: the format similar to the classic thermometer and the one with a dummy.  



Very practical, they indicate the temperature accurately and quickly In addition to being cheap , they are safe and long lasting You can use digital thermometers either rectally (if they have a flexible probe) or oral and axillary. Are they fast? They have a variable measurement time up to a maximum of about 3 minutes. 


Disadvantage: Requires battery. They can de-calibrate.



Liquid crystal thermometers : Easy to use, but not very accurate

How do they work? They are plastic bands that detect the temperature when they touch the forehead. 

Advantages: They are quite easy to use .

Disadvantages : They are not recommended if you are looking for an accurate thermometer.


Infrared thermometers: Fast but delicate

There are three types of this type of infrared thermometers: aural , frontal or remote .


Advantages: The ear is the thermometer that guarantees greater speed In just two seconds it communicates the result. The other two types of infrared thermometer measure the temperature of the forehead by contact or at a distance, thanks to an optical pointer. This new generation of infrared thermometers has the same speed as the ear model, but a degree of precision and ease of use comparable to digital thermometers.  


Disadvantages: It is expensive and not always reliable, as there are factors that interfere with the measurement, such as drops of sweat and the possibility of the patient moving, especially if it is a child. Before using them, always read the instructions for use: if used incorrectly, a reading error of almost 1 ºC may occur.





Curiosity / game: What is the difference between heat and temperature?


The concepts of temperature and heat can be confused. How about a game to understand the difference? Think for yourself what is heat and what is temperature .

Check the respective settings now:


Heat: it is a way of transferring energy from one system to another, being external to the object or body. Heat is defined as energy in motion , that is, it passes from one body to another (from the warmest to the coldest body).

Ex: the heat from the fire is transferred to a pan with water.


Temperature: it is called kinetic energy and is associated with the state of movement or the agitation of the particles that make up the bodies. It allows us to understand hot or cold sensations by measuring with a thermometer, or when touching a body or object.



The difference:

The heat is external to the subject it causes an increase in temperature and evaporation of water. The temperature is internal to the object , such as the sensation of hot and cold or the measurement of them.


The following example makes it easier to clarify the difference between these two concepts. One like boiling water and one bucket of boiling water have the same temperature. However, the bucket of boiling water has a greater amount of energy than the glass of boiling water. Therefore, the amount of heat depends on the mass of the material, the temperature does not.

Although the concepts of heat and temperature are different, they are related. The temperature of a portion of air can change when the air gains or loses heat. However, this is not always necessary, as there may be a change in the phase of the water contained in the air, or a change in the volume of the air portion, associated with heat gain or loss. On the other hand, temperature gradients determine the flow of heat from one place to another through radiation, conduction and convection. 


There are three modes of heat transfer:




Finally, and to make this more fun, can you identify the three forms of heat transfer (1, 2, 3), in the figure below? Leave your answers in the comments. :)



Catarina Vilela - Nurse