Zero on the Faraday scale was equal to modern 32 degrees, and the temperature of the human body was equal to 96 degrees. In 1742, the physicist Celsius made the temperature of melting ice and boiling water the reference points, although initially zero on the scale corresponded to the boiling temperature of water, but then it became the same.

Liquid thermometers operate on the principle of changing the initial volume of liquid poured into the thermometer when changing ambient temperature. Most often, alcohol or mercury is poured into the thermometer flask. Pros mercury thermometer are high accuracy of temperature measurement, long service life, however, the temperature level takes a long time to set, mercury in a thermometer is a dangerous material, so using a mercury thermometer must be done as carefully as possible.
Optical thermometers record temperature based on the level of glow, spectrum and other indicators and are most often used in scientific research.

Mechanical thermometers operate on the principle of liquid thermometers, only the sensor is a spiral or metal tape.
Electrical - they work on the principle of changing the resistance level of the conductor when changing external temperature. Those electric thermometers that have a large range are based on thermocouples - when different metals interact, a contact potential difference arises, which depends on temperature. Electric thermometers have built-in additional memory and backlight functions, they are safe and quickly show results, but they can produce a small error, as a result of which the temperature must be measured several times.

An infrared thermometer measures temperature without direct interaction with a person or object, and is characterized by measurement accuracy and safety, as well as high speed actions - half a second. They are hygienic, work quickly (within 2-5 seconds) and help measure the temperature of children.

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It is known that hotter bodies conduct worse electricity than chilled ones. The reason for this is the so-called thermal resistance metals

What is thermal resistance

Thermal resistance is the resistance of a conductor (section of a circuit) due to the thermal movement of charge carriers. By charges here we must understand the electrons and ions contained in the substance. From the name it is clear that we are talking about the electrical phenomenon of resistance.

The essence of thermal resistance

The physical essence of thermal resistance lies in the dependence of electron mobility on the temperature of the substance (conductor). Let's figure out where this pattern comes from.

Conductivity in metals is provided by free electrons, which, under the influence of electric field acquire directional movement along the electric field lines. Thus, it is reasonable to ask: what can impede the movement of electrons? The metal contains an ionic crystal lattice, which, of course, slows down the transfer of charges from one end of the conductor to the other. It should be noted here that the ions crystal lattice are in oscillatory motion, therefore, they occupy a space limited not by their size, but by the amplitude of their oscillations. Now you need to think about increasing the temperature of the metal. The fact is that the essence of temperature is precisely the vibrations of the ions of the crystal lattice, as well as the thermal movement of free electrons. Thus, by increasing the temperature, we increase the amplitude of vibrations of the ions of the crystal lattice, and therefore create a greater obstacle to the directional movement of electrons. As a result, the resistance of the conductor increases.

On the other hand, as the temperature of the conductor increases, the thermal movement of electrons also increases. This means that their movement is becoming more chaotic than directed. The higher the temperature of the metal, the more degrees of freedom manifest themselves, the direction of which does not coincide with the direction of the electric field. This also causes a greater number of collisions of free electrons with ions of the crystal lattice. Thus, the thermal resistance of a conductor is determined not only by the thermal motion of free electrons, but also by the thermal vibrational motion of the ions of the crystal lattice, which becomes more and more noticeable as the temperature of the metal increases.

From all that has been said, we can conclude that the best conductors are “cold”. It is for this reason that superconductors, whose resistance is zero, contain extremely low temperatures, calculated in Kelvin units.

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Tip 3: Temperature sensor: operating principle and scope of application

Current equipment, automation and automotive industry are unlikely to do without any kind of controllers. This type of device also includes temperature sensors, the scope of which is unlimited.

Device

1. Thermal resistance sensor. Such devices operate on the principle of changing the electrical resistance of a conductor when temperature fluctuations occur. These sensors are easy to use, they are very reliable, sensitive, and more accurate.

2. Semiconductor thermal sensors are designed on the principle of responding to the transformation of the characteristics of a (p-n) junction under the influence of temperature. The series of such sensors is very simple in its design and has an excellent price-durability ratio.

3. Thermoelectric sensors, or thermocouples as they are also called. This type of sensor works on the effect of the temperature difference between a pair of conductors that are in different environments. Due to this, a pulse appears in the closed circuit of this pair of conductors; the sensors signal a change in temperature relative to each other. These devices do not provide the same accuracy as their counterparts described above, and are structurally more cumbersome.

4. Pyrometers. These are non-contact type sensors; they record the temperature near an object. This type of device has the big advantage that it can operate at a distance from the mechanism in which temperature readings need to be recorded.

5. Acoustic sensors. The operating principle is based on the change in the speed of sound in the atmosphere when the temperature of the environment in which the sensor is located changes. Such devices are used in environments where it is impossible to use contact sensors temperature.

6. Piezoelectric sensors. The meaning of the device is as follows: on quartz base, which the sensor itself consists of, delivers a certain series of pulses, thus, with a change in temperature, this material has a different expansion frequency.

Application

The thermometer is special device, designed to measure the current temperature of a specific medium upon contact with it.

Depending on the type and design, it allows you to determine temperature regime air, human body, soil, water and so on.

Modern thermometers are divided into several types. The gradation of devices depending on the scope of application looks like this:

• household;
• technical;
• research;
• meteorological and others.

There are also thermometers:

• mechanical;
• liquid;
• electronic;
• thermoelectric;
• infrared;
• gas.

Each of these devices has its own design, differs in operating principle and scope of application.

Principle of operation

Liquid thermometer

The liquid thermometer is based on an effect known as the expansion of liquid media when heated. Most often, such devices use alcohol or mercury. Although the latter is systematically abandoned due to the increased toxicity of this substance. But still, this process so it is not completely completed, since mercury provides better measurement accuracy, expanding according to a linear principle.

In meteorology, instruments filled with alcohol are often used. This is explained by the properties of mercury: at temperatures of +38 degrees and above, it begins to thicken. In turn, alcohol thermometers allow you to evaluate the temperature regime of a specific environment heated to 600 degrees. The measurement error does not exceed a fraction of one degree.

Mechanical thermometer

Mechanical thermometers are bimetallic or delatometric (rod, rod). The operating principle of such devices is based on the ability of metal bodies to expand when heated. They are highly reliable and accurate. The production cost of mechanical thermometers is relatively low.

These devices are used mainly in specific equipment: alarms, automatic temperature control systems.

Gas thermometer

The operating principle of the thermometer is based on the same properties as the devices described above. Except that in this case an inert gas is used. In fact, such a thermometer is an analogue of a pressure gauge, which is used to measure pressure. Gas appliances used for measuring high and low temperature environments (range is -271 - +1000 degrees). They provide relatively low accuracy, which is why they are abandoned for laboratory measurements.

Digital Thermometer

It is also called a resistance thermometer. The principle of operation of this device is based on changing the properties of a semiconductor built into the design of the device when the temperature increases or decreases. The dependence of both indicators is linear. That is, as the temperature increases, the resistance of the semiconductor increases, and vice versa. The level of the latter directly depends on the type of metal used in the manufacture of the device: platinum “works” at -200 - +750 degrees, copper at -50 - +180 degrees. Electric thermometers are rarely used, since it is very difficult to calibrate the scale during production.

Infrared thermometer

Also known as a pyrometer. It is a non-contact device. The pyrometer operates with temperatures from -100 to +1000 degrees. Its operating principle is based on measuring the absolute value of energy that a specific object emits. The maximum range at which a thermometer is capable of assessing temperature indicators depends on its optical resolution, the type of aiming device and other parameters. Pyrometers are characterized by increased safety and measurement accuracy.

Thermoelectric thermometer

The operation of a thermoelectric thermometer is based on the Seebeck effect, through which the potential difference is assessed when two semiconductors come into contact, resulting in the formation of an electric current. The temperature measurement range is -100 - +2000 degrees.

@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, then there is nothing to break in the mercury thermometer). 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 human body and displays it on a digital display, in a way familiar to us temperature range. 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 seek help from a specialized service center.

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 the sound signal of the device, and not on 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 what you need electronic thermometer you need to get everything you need 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 the battery in an electronic thermometer?

Usually in design electronic thermometer provided 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 shop or at a service center for repairing 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.

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 " Sound signal is not a measurement completion signal. This means your temperature rises, but only slightly. We recommend holding the thermometer after the signal 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 (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 this.

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.

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.