What will the thermometer show? How to use electronic thermometers correctly. Basic rules for measuring temperature

What is a thermometer? If you are interested in this question and want to find a simple and clear answer to it, then welcome! We have written this publication especially for you, which fully covers this topic.

History of creation

In order to understand what a thermometer is, you first need to plunge into the wilds of history. We think the information provided below will be very useful for general development.

The word "thermometer" is translated from Greek as "to measure heat." The first prototype of this device there was a thermoscope, and it was created by the notorious Galileo Galilei in 1957. This invention was a small ball with an attached handle. It was used to determine the temperature of a liquid. Although the thermoscope can be called the first thermometer, its design was very different from its modern counterparts. His testimony directly depended on atmospheric pressure, and not from the mercury scale.

With the development of scientific progress, the thermometer itself changed. In 1667, 110 years after the invention of the thermoscope, a liquid thermometer was first mentioned, and in 1742, the Swedish physicist Celsius invented a thermometer with a scale in which point “0” indicated the freezing point of the liquid, and point “100” indicated its boiling point. .

Types of thermometers

You already know the translation and definition of the word "thermometer", now it's time to talk about existing varieties this device. There are seven types of thermometer in total, and we will devote our own paragraph to each of them.

Liquid thermometer

This device operates due to the effect of expansion of the liquid during its heating. The most famous liquid thermometer is the mercury thermometer. It is often used in medicine to measure body temperature. Although mercury is highly toxic and dangerous substance, it is able to most accurately determine body temperature (which cannot be said about other liquids).

Alcohol thermometers are actively used in meteorology. "Why not mercury?" - you will probably ask. The fact is that when the air temperature reaches 38 degrees Celsius, the mercury inside the device begins to take on a thick form, which is why it stops working.

Gas thermometer

What is a liquid thermometer? We think we were able to give a succinct and informative answer to this question. Now let's talk about gas thermometers, which work on almost the same principle as liquid thermometers. The only difference between them is that gas thermometers use an inert gas instead of a liquid. The range of such devices is from 271 degrees Celsius to 1000 degrees Celsius. As a rule, gas thermometers are used for the primary measurement of the temperature of a substance.

Mechanical thermometer

It works on roughly the same principle as its previously mentioned counterparts. The temperature in it is determined by the expansion of a biometal ribbon and a metal spiral. These types of devices are easy to use and have good reliability. They are often used in automation and alarm systems.

Resistance thermometer

The basis of the operation of this thermometer is the dependence of the conductor on temperature. Metals are used to create these devices. These kinds of thermometers are often used at experimental stands, in laboratories and in production.

Thermoelectric (thermocouple) thermometer

A thermocouple is a contact through which current begins to flow when the temperature changes. The advantages of thermoelectric thermometers include a wide range of measurements, ease of use and the ability to ground the junction. But, unfortunately, there were some downsides. Over time, the thermocouple can rust or undergo other chemical processes that can damage the thermometer. Thermocouples with electrodes made of gold, palladium or some other noble metal have maximum accuracy.

Fiber Optic Thermometer

What is a fiber optic thermometer? This is a sensor based on fiber optics. These devices respond very well to any, even the slightest, changes in the weather. They are actively used in production to ensure safety.

Pyrometer (or infrared thermometer)

The main difference between an infrared thermometer and all previous ones is that it works non-contact. They are often used in production, but in Lately they are increasingly being used in medical purposes. This is not surprising: pyrometers are safer than standard mercury thermometers, and they also take less time to measure temperature.

What is the difference between a thermometer and a thermometer?

The meaning of the word "thermometer", oddly enough, often becomes the subject of discussion among many people. Some people believe that a thermometer and a thermometer are the same device, while others are sure of the opposite. Let's clarify everything once and for all: a thermometer is the same as a thermometer! A thermometer is simply a colloquial name for a thermometer that has taken root among the people. Got it? Go ahead.

What to do if the thermometer is broken?

We have already discussed with you what the word thermometer means and what its types are, but we still haven’t talked about one equally important topic - safety. Sometimes it happens like this: a person began to feel unwell and decided to check his body temperature. He takes out his home first aid kit, takes a thermometer and accidentally drops it on the floor. As a result, this device breaks, and the toxic substance mercury ends up on its floor.

If you accidentally break a thermometer and do not want to be poisoned by toxic mercury vapor, be sure to follow these instructions:

1. Open a window to allow fresh air and better ventilation.
2. Remove all people from the room (especially small children).
3. To reduce the spread of toxic fumes into other rooms, close the door.
4. To reduce spread toxic substances on shoes, it is necessary to lay a special mat or cloth moistened with a solution of potassium permanganate at the entrance.
5. After the above steps, it is strongly recommended to seek the help of specialists and not remove all the mercury manually.

Synonyms for "thermometer"

In fact, there are few synonyms for the word thermometer, and those that exist have already been mentioned several times in this article. But to consolidate the material, we will repeat them again:

• Device.
• Thermometer.
• Device.
• Device.

Bottom line

In our century it is very difficult to imagine life without a thermometer. This universal device is rightfully considered irreplaceable and one of a kind. It occurs many times in everyday life, and it is almost impossible to do without it. The choice of thermometer primarily depends on the scope of its use, size and accuracy.

We hope that the information provided in this article helped you and you learned a lot of new things.

The purchased thermometer shows 1.5 degrees less (35.1 instead of 36.6), what can be done to change the calibration?
Igor, Omsk

Dear Igor, first of all, thank you for choosing our electronic thermometer. Unfortunately, you did not indicate the device model, so I cannot give you exact quotes from the instruction manual for your specific model. I'll take advantage classic instructions for electronic thermometer.

First, a few words about the operating principle of an electronic thermometer. Unlike the classic mercury, where the temperature is indicated due to an increase in the volume of mercury when heated, which by and large makes it unimportant how it is held, you can even cross it under the arm, it will not change anything, in electronic ones - the sensor is located at the end and only the heating of this part affects the temperature (the resistance of the conductor changes depending on the temperature) in the rest of the thermometer there are only wires. Thus, you need to look very carefully at how temperature is measured. The tip should be “stuck into the meat” i.e. firmly “stick” it into the armpit and press firmly with your hand. If the contact is not tight or the sensor is partially free, the temperature will be lower.

Further. The instructions state that "The beep does not indicate the completion of the measurement. This means that your temperature is rising, but only slightly. We recommend holding the thermometer after the beep for a few more seconds." If we translate this into simple language, then after the thermometer beeps, you need to take it out, look at the temperature, hold it there (to be sure for another minute), then look at the indicators and remember the difference. And in the future add this difference to the measurement so as not to wait extra time. Usually the difference is 0.3-0.4 degrees. but the first time you need to check it.

Thus, an incorrect measurement technique and early removal of the thermometer can give an “error” of 1.5 degrees. But when correct use there won't be any problems.

If you doubt the accuracy of the thermometer reading, there is a fantastically simple test - pour a glass of warm water at about body temperature. Or a hot bath. Place the mercury and the tip of an electronic thermometer there. The data will be the same after 3 minutes. This will give you the opportunity to judge how well the thermometer is working. If this test shows that there are problems with the thermometer, contact the service center. I'm sure they can help you.

This all applies to the classic electronic thermometer. If you have an infrared thermometer, then write. I will tell you how to properly maintain and measure with this device. I am sure that all problems can be solved.

It seems that this is clear to everyone - temperature! What is temperature?

One physicist said very well about this: “It is much easier to make measurements than to know exactly what is being measured.” And for almost three hundred years, temperatures were measured everywhere, but only very recently, at the end of the last century, it became finally clear what temperature is.

But really, what does the thermometer show? It is worth once again tracing how the concept of “temperature” arose. It was once thought that if it becomes hot, it is because the caloric content in the body increases. Latin word"temperature" meant "mixture". Body temperature was understood as a mixture of body matter and body caloric. Then the concept of caloric itself was discarded as erroneous, and the word “temperature” remained.

For a good two hundred years, a strange situation remained in science: by a randomly selected property (expansion) of a randomly selected substance (mercury) and a scale established at randomly selected constant points (melting ice and boiling water), the value (temperature), the meaning of the word “temperature” was measured. , strictly speaking, was not clear to anyone.

But the thermometer still shows something, doesn’t it? If the necessary rigor and accuracy are required from the answer, then such a question will have to be answered like this: nothing except elongation in a column of heated mercury.

Well, if mercury is replaced with another substance: a gas or some solid that also expands when heated, what will happen then? What will thermometers built on a different basis show?

Let's imagine that we made such thermometers. We filled some of them with mercury and air, others were made entirely of iron, copper, glass. Let us accurately establish constant points on each of them: in melting ice 0°, in boiling water 100°.

Let's now try to measure the temperature. It will turn out that when the air thermometer shows, for example, 300°, other thermometers will show:

mercury 314.1°,

iron 372.6°,

copper 328.8°,

glass 352.9°.

Which of these “temperatures” is correct: “air”, “mercury”, “iron”, “copper” or “glass”? After all, each of the substances we tested shows its own temperature. A “water” thermometer would behave even more interestingly. In the range from 0° to 4° C, it would show a decrease in temperature when heated.

You can, of course, try to choose, instead of thermal expansion, some other property of a substance that changes when heated. It is possible, for example, to build thermometers based on changes (when heated) in the vapor pressure of a liquid (for example, alcohol), electrical resistance (for example, platinum), thermo electromotive force(thermocouple). Nowadays, such thermometers are widely used in technology.

Subject to preliminary calibration at two constant points, such thermometers, for example, at 200°C will show: alcohol (by vapor pressure) 1320°, platinum (by resistance) 196°, junction of platinum and its alloy with rhodium (thermocouple) 222°.

So which of all these different “temperatures” is the real one? How and with what should you measure temperature?

Before answering these questions, you should understand the most important thing about them - their exact content and meaning: “how to measure temperature.” Why would such a “simple” question even arise?

How do we measure length? Meters. A meter is the length of a standard ruler that scientists

they are stored very carefully so that it does not disappear or deteriorate. How do we measure volumes? Can be measured in liters. A liter is a volume equal to one cubic decimeter. How do we measure temperature?

These questions are completely similar, but the answers to them are fundamentally different. If we pour several buckets into a barrel cold water, then the barrel will be filled with water. The sum of the volumes of water in the buckets will be equal to the volume of the barrel. But no matter how much cold water you pour into the barrel, you won’t get hot water. This reasoning is not at all funny or naive, and this fact is not at all self-evident. This is a very important law of nature, which we are simply accustomed to because we know it from experience. From several short sticks you can make one long one by connecting them end to end. But you cannot add the temperature of a hot coal from a furnace and the temperature of a piece of ice. This will not make the hot coal any hotter.

It is impossible to measure temperature, just as length, volume, and mass are measured, because temperatures do not add up. It is impossible to have a temperature unit that can directly measure any temperature, just as a meter can measure any length. Volume, length, mass are examples of extensive properties of a system. If an iron rod is divided into several parts, the temperature of each of them will not change. Temperature is an example of the intensive properties of a system. It is impossible and meaningless to directly establish a numerical relationship between different temperatures.

But it is necessary to measure the temperature. So how can it be measured if it cannot be measured using a method suitable for measuring extensive quantities?

For this, only one way is possible - to use an objective connection between temperature and any extensive quantity: change in volume, length, deflection of the galvanometer needle, etc.

Therefore, the answer to the question - which of the various “temperatures” listed above is real - may seem strange at first: they are all equal. Any temperature-dependent property of a system can be selected to characterize and measure it.

Thermodynamics was able to indicate the method and substance that allows temperature measurements to be carried out most expediently.

This is an ideal gas. By its expansion at constant pressure or by the increase in pressure at constant volume, temperature measurements can most appropriately be carried out. With this method of measurement, countless expressions for any patterns in nature become the simplest.

But an ideal gas has one significant drawback: such a gas does not exist in nature.

Pressure

How complex and difficult the concept of temperature is, the concept of “pressure” is so simple and clear. Any schoolchild knows it well from the very beginning physics textbook. Pressure is the force acting per unit surface area. The direction of pressure in the case of gases and liquids is always perpendicular to the surface. The concept of “pressure” can be applied to solids, but it follows that the properties of solids can depend on the direction in which the pressure acts (for example, the piezoelectric effect).

In thermodynamics, pressure and temperature are the two main, most important parameters that determine the state of a thermodynamic system. This definition means that the same amount of substance at the same values ​​of temperature and pressure always occupies the same volume. True, it is necessary to add: this definition is valid when an equilibrium state has been achieved in the system.

It is very useful for a chemist to know that one gram-mole of any gas at 0 ° C and at a pressure of 1 atm occupies a volume equal to approximately 22.4 liters. It's worth remembering.

Heat

Probably, hundreds of thousands of years have passed since our distant ancestors first became acquainted with fire and learned to receive heat themselves. Each of us warmed ourselves by the hot stove and froze in the cold. It would seem that what could be more familiar and understandable now than the warmth that is so familiar to everyone.

But the question - what is heat - is far from so simple. The correct answer to this question was found by science quite recently. For a long time scientists did not even notice the complexity of this problem.

The first interpretation of the nature of heat was based on an indisputable and seemingly obvious fact: when a body is heated, its temperature rises - therefore, the body receives heat. When it cools down, the body loses it. Therefore, any heated body is a mixture of the substance of which it consists and heat. The higher the body temperature, the more heat is mixed in it. Nowadays, few people remember that the word “temperature” is translated from Latin and means “mixture”. Once upon a time, for example, they said about bronze that it was “the temperature of tin and copper.”

Two completely different explanations, two hypotheses about the nature of heat have been arguing among themselves in science for almost two centuries.

The first of these hypotheses was expressed in 1613 by the great Galileo. Heat is a substance. It's unusual. It can penetrate into and out of any body. Thermal matter, otherwise caloric, or phlogiston, is not generated or destroyed, but is only redistributed between bodies. The more of it in the body, the higher the body temperature. Not so long ago they used to say “degree of heat” (not temperature), believing that a thermometer measures the strength of a mixture of matter and caloric. (The custom of measuring the strength of wine - a mixture of water and alcohol - in degrees is still preserved.)

The second hypothesis, seemingly completely different from Galileo’s idea, was expressed in 1620 by the famous philosopher Bacon. He drew attention to what has long been known to any blacksmith: under strong blows of a hammer, a cold piece of iron becomes hot. There is a known method of producing fire by friction. This means that by impact and friction it is possible to produce heat without receiving it from an already heated body. Bacon concluded from this that heat is the internal movement of the smallest particles of a body and the temperature of a body is determined by the speed of movement of the particles in it. This theory is called in science the mechanical theory of heat. The brilliant Lomonosov did a lot to substantiate and develop it.

Despite the fundamental divergence, both hypotheses have many similarities: from the theory of caloric it followed that the thermometer measures the amount of caloric contained in the body, but according to the mechanical theory of heat, the thermometer shows the amount of motion contained in the body. According to both theories, absolute zero temperature must exist. It will be achieved when, according to the theory of caloric, all the caloric is taken away from the body, and according to the mechanical theory, when the body loses all the motion contained in it.

The caloric theory dominated science for almost two centuries. It is simple and clear. But she is wrong. Accurate weighing of bodies different temperatures showed that heat is weightless. The weightlessness of heat was in good agreement with the mechanical theory of heat. Then they thought that movement could in no way affect the weight of the body. However, now we know that this is not accurate. Energy, according to Einstein's law, must have mass and, therefore, also “weighs”; only the corresponding weight gain lies far beyond even modern weighing accuracy.

Heat should not be confused with the thermal energy of the body. The thermal energy of a body is determined by the kinetic energy of movement of its molecules. But heat (this is very important) is far from equal to thermal energy. And more importantly, heat is not contained in the body at all. There was no heat at all from the wood burning in the stove. Heat only enters or leaves the body.

It is not at all difficult to calculate the amount of energy of chaotic thermal motion in a system consisting of molecules of superheated water vapor - this will be its thermal energy. But the amount of heat that can be released from this system when it cools is not at all equal to thermal energy: first the steam will cool, then it will begin to condense into liquid water, then the water will cool and finally the water will freeze. The heat of evaporation of water and the heat of melting of ice are very high. Thus, much more heat can be obtained from superheated steam than the thermal energy it contains.

Therefore, strictly speaking, both hypotheses are incorrect - neither the idea of ​​heat as a thermal substance, nor the mechanical theory of heat. The second of them is confirmed by experience, but it has nothing to do with heat and concerns only thermal energy, and this is not the same thing.

Job

To perform mechanical work means to overcome or destroy resistance: molecular forces, spring force, gravity, inertia of matter, etc. To abrade, grind a body, divide it into parts, lift loads, pull a cart along the road,

there is a train on the rails, compressing a spring - all this means doing work; it means overcoming resistance for some time. To do work means to overcome the resistance of gas, liquid, solid, crystal. Compressing a gas, liquid, or crystal means doing work.

The same name “work” is used to name dissimilar phenomena, but behind the external differences one must see common basic features. The work involves movement: the load is lifted, the cart moves, the piston slides in the engine cylinder. Without movement there is no work.

Work involves orderly movement. The entire load moves upward. The entire cart moves along the road in one direction. The entire piston moves in one direction in the cylinder. The work is impossible without two participants. To raise one load, another weight must fall, the spring must straighten, and the gas must expand. Both participants move ordering. Work is the transfer of ordered movement from one system to another.

One should not think that work can only be related to mechanical movement. Work can also be performed when the electric or magnetic field changes.

The ability of a system to do work is, of course, very important for thermodynamics. But exactly what work the system can do is unimportant for thermodynamics. How exactly this work can be calculated and how it can be measured must be said by another science.

The definition of mechanical work is given by mechanics. Every schoolchild knows this definition: work (A) is equal to the product of force (F) and path (l).

If the force is not constant, then you have to calculate the amount of work on each sufficiently small section of the path (mathematicians say - on an infinitesimal) on which the force can be considered constant

dA=Fdl,

and then sum up the infinitesimal values ​​of work along the entire path traveled:

For those who have not yet weaned themselves from being afraid of mathematical formulas, it is useful to remember that the integral sign ∫ is simply an elongated letter S - the initial one in the word “sum”.

IN physical chemistry processes associated with the crushing of a substance into a fine powder (dust) or the emergence from steam are often considered new phase fog or smoke. With such processes, a huge new surface of many tiny particles appears, and considerable work must be spent on its formation. This work cannot be ignored. It is equal to the product of surface tension (a) and the area of ​​the new surface (S):

This kind of work is also required when blowing a soap bubble.

Heat engineering, when calculating the work of any heat engine, uses the amount of work done by an expanding gas, for example, water vapor in the cylinder of a steam locomotive or in a turbine. This very important type of work is measured by the product of gas pressure and the change in its volume:

Electrochemistry, for example, knows a different type of work. Electrical work battery or galvanic cell is equal to the product of the electromotive force (E) and the change in charge (q):

It is useful to notice and remember that all expressions for various types the works are very similar to each other. Any work is necessarily measured by the product of two factors: some generalized force / (this can be force universal gravity, magnetic strength or electric field, pressure, surface tension, any mechanical forces, etc.) and values ​​a - changes in the corresponding system parameter (distance traveled, electric charges, surface size, volume, etc.):

A=∫fda.

It is not the task of thermodynamics to study the difference between different types work. Other sciences must take care of this. Various works there can be a lot. There is only one warmth.

@Let's figure it out girls!!! What kind of thermometer is better for measuring BT? I suggest reading the article first. And express your opinion.
From today I am giving my choice in favor of mercury because I noticed that the electronic one is lying and not by 1-2 degrees, but it has happened differently by 5
ARTICLE

A person's body temperature is one of the main indicators of his health. Deviation from the normal temperature of a person is directly related to problems in his health. There probably won’t be a person who doesn’t know how, and most importantly, how to measure temperature.

Today in pharmacies and specialty stores medical equipment, and supermarkets household appliances and electronics, presented a large number of all kinds of thermometers (thermometers) - mercury, electronic and infrared, non-contact and contact, disposable and with replaceable attachments. Each of them has both its advantages and disadvantages.

Traditional mercury thermometer long years will not go away from our everyday life. Despite the advent of accurate electronic thermometers, many still trust only a mercury thermometer. A mercury thermometer is a glass flask with a capillary that contains mercury (2 grams).

It got its name “maximum” due to the fact that the mercury column, after heating, remains at its highest heating point and does not fall when cooled. To return it to its initial position, you just need to shake this thermometer.

Advantages:

High accuracy of temperature measurement (permissible error no more than 0.1 degrees).

A variety of ways to measure temperature (in the armpit, orally, rectally).

Long service life (if you do not drop the thermometer and handle it carefully, it will break in mercury thermometer nothing). It does not require periodic replacement of batteries.

There are no problems with disinfection (but you cannot boil).

Low cost of a thermometer (15–25 rubles).

Flaws:

The very fragile and unreliable design of the case makes it easy to break the thermometer, which will inevitably lead to contamination with poisonous mercury and glass fragments.

Long-term temperature measurement - about 10 minutes.

The streamlined shape increases the risk of “losing” the thermometer during rectal measurement.

It is not recommended for small children to use it orally.

An electronic thermometer measures body temperature using a special built-in sensitive sensor, and displays the measurement result digitally on the display.

Electronic thermometers have a number of additional functions in the form of a memory of the last measurements, sound signals based on the time of measurement and measurement results, replaceable tips for hygienic use, waterproof housing, etc.

But for more precise measurement body temperature, electronic thermometers will require closer contact of the measuring sensor with the surface of the human body.

Advantages:

First of all, safety of use: there is no mercury in this thermometer and it cannot be broken.

Prostate reading temperature results.

Very short temperature measurement time, only 30–60 seconds. But in the case of measuring the temperature in the armpit, the time increases to 1.5–3 minutes.

Automatically turns off after a certain time.

Illuminated thermometers can be used even in the dark.

Almost everything modern models, there is a memory that stores the history of the latest measurements (from 1 to 25).

There is an interchangeable Celsius-Fahrenteit measurement scale.

A large number of different models, various forms and flowers. There are special fashions for children, with bright colors or in the form of a pacifier, with flexible, low-traumatic tips.

Flaws:

It is necessary to strictly follow the instructions when using the thermometer and measuring temperature.

When measuring temperature in the armpit, to obtain the most accurate results, the temperature measurement time is significantly longer than the minimum stated. Moreover, in most models, there is a strict rule in the instructions “after the sound signal about the end of the measurement, you should hold the thermometer for so many minutes.” Consequently, the time of temperature measurement must be recorded separately, which is very inconvenient.

Most models, especially cheap household models, cannot be washed or disinfected. This possibility must be clarified at the time of purchase by asking a sales consultant or reading the operating instructions for the thermometer.

Requires periodic replacement of batteries. Although regular batteries last for 2-5 years, depending on the frequency of use, they can run out of charge at the most inopportune moment. Therefore, it is advisable to always have a set of spare batteries.

The price of electronic thermometers ranges from 150 to 1,000 rubles. True, this is the amount of much correct demercurization of the room in the case of a broken mercury thermometer.

The operating principle of an infrared thermometer: a sensitive measuring element takes data infrared radiation of the human body and displays it on a digital display in the temperature range familiar to us. This type thermometers appeared quite recently, but have already gained popularity.

Advantages:

Has all the basic functions of electronic thermometers (measurement memory, sound signals, auto shutdown, etc.).

Measures temperature very quickly (only 5–30 seconds).

Replaceable tips allow you to solve problems of disinfection and hygiene.

The non-contact model allows you to measure the temperature even of crying children and sleeping patients.

Flaws:

Depending on the measurement conditions, there may be a large error, and in cheap models the measurement accuracy can exceed 0.3–0.5 degrees.

Temperature can only be measured in certain parts body (forehead, ears, temples).

In case of inflammation of the middle ear, ear models give inaccurate results.

Also unreliable measurement results for a screaming or crying child.

Requires periodic verification.

There are known cases of injury to the eardrum due to careless handling of the thermometer.

High cost (from 1,300 to 5,000 rubles).

Thermal strip is a heat-sensitive film. The thermal strip, thanks to the crystals it contains, can change its color under the influence of body temperature.

Thermal strips have a large measurement error. This is due to the fact that there are many factors that influence the measurement: light, the presence of sweat, tightness to the surface of the skin, etc.

Thermal strips come in different designs. They may be divided into “elevated temperature” or “not elevated temperature”. That is, they signal whether it is necessary to measure the temperature with a real thermometer, which will show the exact temperature, or not.

The need for thermal strips may arise during road conditions, so when going on vacation or a trip, stock up on thermal strips. Since thermal strips do not take up any space and weigh almost nothing, they will not cause you any problems, and will be very useful if necessary.

Despite the fact that electronic thermometers have recently come into use, there is a well-established stereotype that electronic thermometers lie, and mercury thermometers show the real temperature. But in fact, it is not the devices that make mistakes, but people who do not know how to use them and do not read the instructions for use.

Of course, it cannot be said that all digital instruments have very high accuracy. Counterfeit thermometers often go on sale famous manufacturers, especially if you buy them not at a pharmacy, but at a regular supermarket for household appliances and electronics. Sometimes there are batches of devices in which the measuring sensors may be incorrectly configured, the device may have been subject to overloads, shocks or shocks, or simply be of poor quality.

For your peace of mind and confidence in the correctness of the thermometer readings, it is better to compare the readings with another thermometer immediately after purchase, or contact a specialized service center for help.

Exist general methods which will help any thermometer, even the most accurate, show the wrong temperature:

If you measure your temperature orally, then before measuring your temperature, drink hot tea or eat hot food, or vice versa, drink a soft drink and eat ice cream.

When measuring the temperature in the armpit – Accept cold shower or a hot bath.

Leave your armpit sweaty before taking your temperature.

Hold the mercury or electronic thermometer loosely in the armpit.

Use a pacifier thermometer to measure the temperature of a screaming baby.

Place the sensitive part (measuring sensor) of the device in the wrong place.

Take your temperature rectally without first emptying your rectum.

Focus on sound signal device, and not when, according to the instructions, it will show the exact result.

Measure the temperature for less than the set time.

Where is the best place to buy a thermometer?

Mercury thermometers are usually sold at pharmacies. Electronic thermometers are also sold in pharmacies, but it is better to buy electronic thermometers in specialized medical equipment stores, especially complex models. In such a specialized store, sellers will be able to give you qualified consultation about different models of thermometers and explain the rules for their use. The pharmacy will sell you a high-quality thermometer, but detailed instructions you won't be able to get it.

You should not buy thermometers in supermarkets of household appliances and electronics. Models of electronic thermometers that are sold in pharmacies undergo appropriate certification and guarantee correct temperature measurement. The same models of thermometers that are sold in supermarkets do not guarantee measurement accuracy.

It is worth remembering that thermometers belong to the group of goods that cannot be returned. Of course, if the device is defective or faulty, it will be replaced, repaired, or your money returned, but only after an appropriate examination has been carried out. But if you don’t like the model of the thermometer or its functionality, nothing can be done. Therefore, before purchasing the electronic thermometer you need, you need to get all the necessary and useful information to decide if it's right for you this model thermometer or not.

Rules for measuring body temperature using an electronic thermometer

To accurately measure body temperature, it is necessary to ensure the tightest possible fit of the measuring sensor to the surface of the skin to ensure better heat transfer. It is recommended to measure the temperature in the mouth or rectum (temperature measurements in the rectum are most consistent with the actual temperature).

If you measure the temperature in the armpit, then you should place the thermometer vertically, that is, along the axis of the body, and not perpendicularly, as usual. Or follow the following temperature measurement algorithm:

Before measuring the temperature, wipe the armpit dry.

Raise a hand

Place the thermometer perpendicular to the surface of the armpit

Slowly lowering your hand, without lifting the sensor from the skin, bring the thermometer to its normal position.

Place your arm close to your body or lie on your side.

For a more accurate measurement, you need to hold the thermometer under your armpit for longer than what is written in the instructions. Ignore if the beep appears earlier.

Questions and answers on the operation of electronic thermometers

How to replace in electronic thermometer battery?

Typically, the design of an electronic thermometer provides easy way replacing the battery. Usually the battery is closed with a small cap, which is attached to a latch or a small bolt. If necessary, you can replace the battery in the electronic thermometer at any watch repair shop, or service center for repair of household appliances.

Why do you need an electronic thermometer if you already have a mercury thermometer?

The main advantage of electronic thermometers compared to a traditional mercury thermometer is that they do not contain mercury. If a mercury thermometer is broken, mercury pollutes the surrounding space and can enter the body and lead to severe poisoning, because mercury is a highly toxic poison.

How to check the accuracy of measurements of electronic thermometers at home?

It is very easy to check the readings of an electronic thermometer at home. It is necessary to compare the readings of an electronic thermometer with the readings of a mercury thermometer when measuring the temperature in a certain environment.

Pour warm water into a glass. Place a mercury and an electronic thermometer in a glass so that the measuring element of the electronic thermometer and the mercury flask of the mercury thermometer are at the same level.

Wait 10 minutes.

After the readings on the mercury thermometer stop changing, compare the readings of the thermometers. If the difference in readings between thermometers does not exceed 0.1 degrees, then the electronic thermometer is working.

How can you explain the low readings on an electronic thermometer?

Low readings on an electronic thermometer are associated with a loose fit of the measuring element to the skin. Therefore, to accurately measure body temperature, it is necessary to ensure close contact between the skin and the measuring element of the thermometer. In this case, you must hold the thermometer in a tight touch during the entire time of measuring the temperature.

Which has already described a similar device, but not for measuring degrees of heat, but for raising water by heating. The thermoscope was a small glass ball with a glass tube soldered to it. The ball was slightly heated and the end of the tube was lowered into a vessel with water. After some time, the air in the ball cooled, its pressure decreased and the water, under the influence of atmospheric pressure, rose up in the tube to a certain height. Subsequently, with warming, the air pressure in the ball increased and the water level in the tube decreased as it cooled, but the water in it rose. Using a thermoscope, it was possible to judge only the change in the degree of heating of the body: numerical values it did not show the temperature, since it did not have a scale. In addition, the water level in the tube depended not only on temperature, but also on atmospheric pressure. In 1657, Galileo's thermoscope was improved by Florentine scientists. They equipped the device with a bead scale and pumped out the air from the reservoir (ball) and tube. This made it possible not only to qualitatively, but also quantitatively compare body temperatures. Subsequently, the thermoscope was changed: it was turned upside down, and instead of water, alcohol was poured into the tube and the vessel was removed. The operation of this device was based on the expansion of measures; the temperatures of the hottest summer and coldest winter days were taken as “constant” points. The invention of the thermometer is also attributed to Lord Bacon, Robert Fludd, Sanctorius, Scarpi, Cornelius Drebbel ( Cornelius Drebbel), Porte and Salomon de Caus, who wrote later and partly had personal relations with Galileo. All these thermometers were air thermometers and consisted of a vessel with a tube containing air separated from the atmosphere by a column of water; they changed their readings both from changes in temperature and from changes in atmospheric pressure.

Mercury medical thermometer

Thermometers with liquid are described for the first time in the city "Saggi di naturale esperienze fatte nell'Accademia del Cimento", where they are spoken of as objects that have long been made by skilled artisans, called "Confia", who heat the glass on the blown fire of a lamp and make It makes amazing and very delicate products. At first these thermometers were filled with water, and they burst when it froze; The use of wine alcohol for this purpose began in 1654 at the thought of the Grand Duke of Tuscany Ferdinand II. The Florentine thermometers are not only depicted in the Saggi, but have been preserved in several copies to this day in the Galilean Museum, in Florence; their preparation is described in detail.

First, the master had to make divisions on the tube, taking into account its relative sizes and the dimensions of the ball: the divisions were applied with molten enamel onto the tube heated in a lamp, every tenth was indicated by a white dot, and the others by black. Usually, 50 divisions were made so that when the snow melts, the alcohol does not fall below 10, and in the sun it does not rise above 40. Good masters made such thermometers so successfully that they all showed the same temperature value at the same conditions, however, this could not be achieved if the tube was divided into 100 or 300 parts in order to obtain greater accuracy. The thermometers were filled by heating the ball and lowering the end of the tube into alcohol; the filling was completed using a glass funnel with a thin end that fit freely into a fairly wide tube. After adjusting the amount of liquid, the opening of the tube was sealed with sealing wax, called "sealant". From this it is clear that these thermometers were large and could be used to determine air temperature, but they were still inconvenient for other, more diverse experiments, and the degrees of different thermometers were not comparable with each other.

The Swedish physicist Celsius finally established both constant points, melting ice and boiling water, in 1742, but initially he put 0° at the boiling point, and 100° at the freezing point, and adopted the reverse designation only on the advice of M. Störmer. Surviving examples of Fahrenheit thermometers are distinguished by their meticulous execution. However, the “inverted” scale turned out to be more convenient, on which the melting temperature of ice was designated 0 C, and the boiling point 100 C. Such a thermometer was first used by Swedish scientists, botanist K. Linnaeus and astronomer M. Stremer. This thermometer is widely used.

Mechanical thermometers

Mechanical thermometer

Window mechanical thermometer

This type of thermometer operates on the same principle as liquid thermometers, but a metal spiral or bimetallic tape is usually used as a sensor.

Electric thermometers

Medical electric thermometer

The operating principle of electric thermometers is based on the change in conductor resistance when the ambient temperature changes.

The wider range of electrical thermometers are based on thermocouples (contact between metals of different electronegativity creates a temperature-dependent contact potential difference).

Home weather station

The most accurate and stable over time are resistance thermometers based on platinum wire or platinum coating on ceramics. The most widely used are PT100 (resistance at 0 °C - 100Ω) PT1000 (resistance at 0 °C - 1000Ω) (IEC751). The dependence on temperature is almost linear and obeys a quadratic law at positive temperatures and a fourth-degree equation at negative temperatures (the corresponding constants are very small, and to a first approximation this dependence can be considered linear). Temperature Range−200 - +850 °C.

Hence, the resistance at T°C, resistance at 0 °C, and constants (for platinum resistance) -

Optical thermometers

Optical thermometers allow you to record temperature by changing the luminosity level, spectrum and other parameters (see Fiber Optic Temperature Measurement) as the temperature changes. For example, infrared body temperature meters.

Infrared thermometers

An infrared thermometer allows you to measure temperature without direct contact with a person. In some countries, there has long been a tendency to abandon mercury thermometers in favor of infrared ones, not only in medical institutions, but also at the everyday level.

An infrared thermometer has a number of undeniable advantages, namely:

• safety of use (even with serious mechanical damage there is no threat to health)
• higher measurement accuracy
• minimum procedure time (measurement is carried out within 0.5 seconds)
• possibility of group data collection

Technical thermometers

Technical liquid thermometers are used at enterprises in agriculture, petrochemical, chemical, mining and metallurgical industries, mechanical engineering, housing public utilities, transport, construction, medicine, in short, in all areas of life.

There are the following types of technical thermometers:

• technical liquid thermometers TTZh-M;
• bimetallic thermometers TB, TBT, TBI;
• agricultural thermometers TS-7-M1;
• maximum thermometers SP-83 M;
• low-degree thermometers for special chambers SP-100;
• special vibration-resistant thermometers SP-V;
• mercury thermometers, electric contact TPK;
• laboratory thermometers TLS;
• thermometers for petroleum products TN;
• thermometers for testing petroleum products TIN1, TIN2, TIN3, TIN4.