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Does the thermometer show the wrong temperature? What is a thermometer? Water thermometers

Where do you take your temperature? Under your arm? In vain - it's not the best place. Experts from Örebro University (Sweden) were able to help us decide where to put the thermometer at the first symptoms of influenza and acute respiratory infections. During the study, they measured the temperature of volunteers in the armpit, mouth, ear, vagina and rectum. And who do you think won?

323 patients University clinic bravely endured the hardships of the experiment. As it turned out, not in vain. In the end, the word “shove” really turned out to be the most appropriate. Scientists have received convincing evidence that the most accurate result is obtained by measuring the temperature in the rectum.

According to scientists, the readings of ear thermometry are distorted by hair and earwax, it is quite difficult to hold the thermometer in the mouth correctly, and the result of axillary thermometry is affected by deodorant and clothing. But measuring degrees in the rectum may not be very convenient, but it is accurate.

Vaginal thermometry also gives the correct result, but statistics prevented this method from being called the most preferable.


Normal temperature readings

    02.08.2016 - 31.08.2020

    405d left.

    And so, here you go normal indicators temperature at in different ways measurements:

    • - oral - 35.7-37.3;
    • - rectal - 36.2-37.7,
    • - axillary (in the armpits) - 35.2-36.7.
    • - inguinal fold 36.3°-36.9°C.
    • - vagina - 36.7°-37.5°C

    Important: Oral and rectal temperature measurements are more accurate than armpit temperatures.

    The most familiar method of measurement, axillary, by the way, turned out to be the most inaccurate. The normal armpit temperature starts not from 36.6°, but from 36.3° C. Normally, the difference between the armpits is from 0.1 to 0.3° C. So it turns out that an error of 0.5° for axillary thermometry is common. And if the thermometer shows 36.9° for several days, but you actually have 37.4°, this can already be dangerous.

    Basic rules for measuring temperature


    If you are not ready to change your habits, then here you go 10 Basic Rules for Temperature Measurement.

    1. 1. The temperature in the room should be 18-25 degrees. If less, you first need to warm the thermometer in your palms for about half a minute.
    2. 2. Wipe the armpit with a napkin or dry towel. Doing so will significantly reduce the likelihood of the meter cooling due to sweat evaporation.
    3. 3. Don’t forget to shake the mercury thermometer or turn on the electronic one (Gamma, Omron, Microlife).
    4. 4. The metal tip of the electronic thermometer (or the mercury column of a regular one) should fall into the deepest point of the cavity, in close contact with the body. It is worth noting that the junction density must be maintained throughout the entire measurement period.
    5. 5. The temperature is not measured immediately after the walk, physical activity, a hearty lunch, hot tea, a warm bath and nervous overexcitation (for example, if the child cried for a long time). You need to wait 10-15 minutes.
    6. 6. During the measurement you cannot move, talk, eat or drink.
    7. 7. Measurement time for mercury thermometer - 6-10 minutes, electronic - 1-3 minutes. Remember: electronic thermometers are safer than mercury thermometers.
    8. 8. You need to take out the thermometer smoothly - due to friction with the skin, a few tenths of a degree may be added.
    9. 9. During illness, you need to measure your temperature in the morning (7-9 am) and in the evening (between 5 pm and 9 pm). It is important to do this at the same time, before taking antipyretic medications or 30-40 minutes after.
    10. 10. If the thermometer is used by all family members, it should be wiped with a disinfectant solution and wiped dry after each use.

    Question answer

    The therapist answers questions highest category Sulimanova Elena Petrovna

    Why do the readings of an electronic thermometer sometimes differ from those of a mercury thermometer?

    Because we are using the first one incorrectly. After the device beeps, you need to hold it for about a minute - then the result will be correct.

    How to properly hold a thermometer under your arm?

    The thermometer sensor must be positioned exactly in the middle of the armpit.

    To obtain an accurate result, the temperature sensor of the electronic thermometer should fit as tightly as possible to the skin under the armpit. The hand must be pressed tightly against the body until the measurement is completed.

    Under which armpit is it correct to measure the temperature?

    There is no difference, usually it is the armpit of the non-working arm, but I repeat, there is no difference. There is a slight difference when you measure your blood pressure.

    How to measure temperature without a thermometer?

    With lips, touching lips to the forehead of the sick person. If heat is really present, it will be simply impossible not to feel it in this situation. The lips, unlike the hand, with which you can also try to measure the temperature, are more sensitive.

    Another way to determine fever without a thermometer is to determine your pulse rate. According to medical research, when people's body temperature increases by 1 degree, their pulse is proportionally capable of increasing by approximately 10 beats per minute. Therefore, a high pulse rate may be a direct consequence of the patient's fever.

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.

Thermometers are well known to almost every person as tools that provide information about the temperature in a particular environment. Despite the simplicity of the task, manufacturers produce this device in different variations, differing in design and performance characteristics.

A modern thermometer is an ergonomic measuring device that presents the climatic indicators of the target environment in a user-friendly form. At least, this is the perception of their products that the developers of this device strive for.

General information about thermometers

Externally, most measuring instruments of this type are small devices, the filling of which is focused on recording a certain type of vibration of the sensitive element. Classic example is an oblong tube containing liquid enclosed in a glass body. People call it a thermometer. It can also be used in medical purposes, and for tracking outside temperature. In this case, the measurement principle is based on the ability of a liquid to expand under the influence of heat. It is also popular. This is also a compact device that records temperature readings using a sensitive element in the form of a sensor. Such models are inferior to mercury analogues due to the high degree of error, but they are completely safe and easy to use.

Classifications of thermometers

There are many parameters by which thermometers are divided, and the above representatives of this group of measuring instruments illustrate only two examples of their implementation. One of the main classifications is the division by work environment. On the market you can find thermometers aimed at making measurements in air, soil, water, living bodies, etc. Based on the principle of operation of the sensitive element, traditional liquid, electronic, gas and mechanical devices. More modern ones include infrared, digital and optical devices. It is important not to forget that measuring device must not only record values ​​in a certain way, but also provide them in one form or another. In this sense, a thermometer is a device that reflects indicators in the form of a scale or using an electronic display. Digital models are gradually replacing analogues with mechanically data presentation, but they lose in terms of accuracy of readings.

Water thermometers

Such models are called aquarium thermometers, with the help of which the user can evaluate the temperature regime in aquatic environment. Devices of this type are available in two versions. The more common water thermometer is a liquid-type device in which alcohol serves as an indicator instead of mercury. Since the measurement technique involves immersion in the middle layers of water, hazardous toxic substances are not used in liquid models.

The second version of water thermometers is a patch-on adhesive device. That is, it is not immersed directly in the medium, but is fixed on the wall of the tank. The measuring principle is based on the properties of some substances in a liquid to change their qualities depending on the intensity of heating. The adhesive water thermometer is provided with thermochemical paint, presented in the form of a temperature scale. The advantages of this type of device include mechanical stability, installation flexibility and safety. However, this thermometer is not capable of providing high measurement accuracy - especially if there are active heat sources near the water container.

Manometric thermometer

This is a separate group whose operating principle is associated with recording pressure indicators in a particular substance or environment. Actually, the change in pressure under the influence of temperature performs the function of a sensitive element. Another thing is that the pressure itself is recorded and converted to a temperature scale after being measured through a complex pressure gauge device. Typically, a system is used for this by combining an immersed sensing element, tubular spring and capillary wire. Depending on temperature fluctuations, the pressure in the target submerged object changes. The manometric thermometer reflects the slightest deviation in the indicator through a pointer mechanism. Depending on the type of working substance, gas, condensation and liquid devices are distinguished.

Multifunctional thermometers

In a sense, the above-mentioned manometric apparatus can also be included in this group of thermometers. It allows you to obtain not one, but several measured values ​​- in particular, pressure and temperature. However, pressure gauges most often use the principle of measuring pressure only as an auxiliary operation to record the main indicator in the form of temperature. Full-fledged multifunctional devices allow you to separately monitor several indicators, including pressure, humidity and even wind speed. This is a kind that provides a barometer, thermometer, hygrometer and other measuring components.

As a rule, such complexes are used by fishermen, travelers and employees of specialized enterprises whose work depends on external conditions. Stations are also mechanical and electronic, which determines their accuracy and ease of use.

Thermometer with remote sensor

Such devices provide for the presence of a special conductor through which information received through a sensitive sensor is transmitted. That is, the base of the device is a panel with an interface and a display through which the user learns about temperature indicators. And the sensor, in turn, can be placed directly in the target environment. Such models are usually used to determine temperature regime in the same aquariums or on the street. In this case, the thermometer with the sensor can also work via wireless communication. In this case, the sensor itself will be more massive, since its power supply will require a special niche for a battery or batteries.

@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: lighting, 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 electronic thermometer OK

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 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.

About removing spilled mercury from broken thermometer see article Demercurization

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.