Why does a person need measurements? Measurements are one of the most important things in... Why do you need to measure blood pressure?

Metrology - the science of measurements

Metrology is the science of measurements, methods and means of ensuring their unity and ways of achieving the required accuracy.
This is a science that deals with establishing units of measurement of various physical quantities and reproducing their standards, developing methods for measuring physical quantities, as well as analyzing the accuracy of measurements and investigating and eliminating the causes of errors in measurements.

In practical life, people deal with measurements everywhere. Measurements of such quantities as length, volume, weight, time, etc. are encountered at every step and have been known since time immemorial. Of course, the methods and means of measuring these quantities in ancient times were primitive and imperfect, however, without them it is impossible to imagine the evolution of Homo sapiens .

The importance of measurements in modern society is great. They serve not only as the basis of scientific and technical knowledge, but are of paramount importance for accounting of material resources and planning, for domestic and foreign trade, for ensuring product quality, interchangeability of components and parts and improving technology, for ensuring labor safety and other types of human activity.

Metrology is of great importance for the progress of natural and technical sciences, since increasing the accuracy of measurements is one of the means of improving the ways of human knowledge of nature, discoveries and practical application of precise knowledge.
To ensure scientific and technological progress, metrology must be ahead of other areas of science and technology in its development, because for each of them, accurate measurements are one of the main ways to improve them.

Objectives of the science of metrology

Since metrology studies methods and means of measuring physical quantities with the maximum degree of accuracy, its tasks and goals follow from the very definition of science. However, given the enormous importance of metrology as a science for scientific and technological progress and the evolution of human society, all terms and definitions of metrology, including its goals and objectives, are standardized through regulatory documents - GOST ov.
So, the main tasks of metrology (according to GOST 16263-70) are:

establishment of units of physical quantities, state standards and standard measuring instruments;
development of theory, methods and means of measurement and control;
ensuring uniformity of measurements and uniform measuring instruments;
development of methods for assessing errors, the state of measuring and control equipment;
development of methods for transferring unit sizes from standards or reference measuring instruments to working measuring instruments.

Brief history of the development of metrology

The need for measurements has arisen since time immemorial. For this purpose, improvised means were primarily used.
For example, the unit of weight of precious stones is the carat, which translated from the languages of the ancient southeast means “bean seed”, “pea”; unit of pharmaceutical weight is gran, which translated from Latin, French, English, Spanish means “grain”.

Many measures were of anthropometric origin or were related to a person’s specific work activity.
So, in Kievan Rus they used vershok - the length of the phalanx of the index finger; span - the distance between the ends of the outstretched thumb and index fingers; elbow - the distance from the elbow to the end of the middle finger; fathom - from “to reach”, “to reach”, i.e. you can reach it; oblique fathom - the limit of what can be reached: the distance from the sole of the left foot to the end of the middle finger of the right hand extended upward; verst - from “turn”, “turning” the plow back, the length of the furrow.

The ancient Babylonians established the year, month, hour. Subsequently, 1/86400 of the average period of revolution of the Earth around its axis was called a second.
In Babylon in the 2nd century. BC e. time was measured in minutes. Mina equaled the period of time (equal to approximately two astronomical hours), during which a “mine” of water flowed from the water clock adopted in Babylon, the mass of which was about 500 d. Then the mine shrank and turned into the familiar minute.
Over time, water clocks gave way to sand clocks and then to more complex pendulum mechanisms.

The most important metrological document in Russia is the Dvina Charter of Ivan the Terrible (1550). It regulates the rules for storing and transferring the size of a new measure of bulk solids - octopus. Its copper copies were sent throughout the cities for the safekeeping of elected people - elders, sotskys, tselovalniks. From these measures it was necessary to make branded wooden copies for city measurers, and from those, in turn, wooden copies for use in everyday life.

The metrological reform of Peter I allowed English measures to be used in Russia, which became especially widespread in the navy and shipbuilding - feet, inches.
In 1736, by decision of the Senate, the Commission of Weights and Measures was formed under the chairmanship of the chief director of the Mint, Count M.G. Golovkin. The commission included an outstanding scientist of the 18th century, a contemporary of M.V. Lomonosov, Leonhard Euler, who made an invaluable contribution to the development of many sciences.
As initial measures, the commission produced a copper arshin and a wooden fathom; a bucket from the Moscow Kamennomostsky drinking yard was taken as the measure of substances. The most important step that summed up the work of the commission was the creation of the Russian reference pound.

The idea of constructing a measurement system on a decimal basis belongs to the French astronomer G. Mouton, who lived in the 17th century. Later it was proposed to adopt one forty millionth of the earth's meridian as a unit of length. On the basis of a single unit - the meter - the entire system, called metric, was built.

In Russia, the decree “On the System of Russian Weights and Measures” (1835) approved the standards of length and mass - the platinum fathom and the platinum pound.
In accordance with the International Metrological Convention, signed in 1875, Russia received platinum-iridium mass unit standards № 12 And 26 and standards of units of length № 11 And 28 , which were delivered to the new building of the Depot of Exemplary Weights and Measures.
In 1892, D.I. was appointed manager of the Depot. Mendeleev, which in 1893 he transformed into the Main Chamber of Weights and Measures - one of the world's first metrological research institutions.

The metric system in Russia was introduced in 1918 by the decree of the Council of People's Commissars “On the introduction of the International Metric System of Weights and Measures.” The further development of metrology in Russia is associated with the creation of a system and bodies of standardization services.

The development of natural sciences led to the emergence of more and more new measuring instruments, and they, in turn, stimulated the development of sciences, becoming an increasingly powerful means of their advancement.

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The merits of physics cannot be overestimated. Being a science that studies the most general and fundamental laws of the world around us, it has changed human life beyond recognition. Once upon a time, the terms “” and “” were synonymous, since both disciplines were aimed at understanding the universe and the laws that govern it. But later, with the beginning of scientific research, physics became a separate scientific field. So what did she give to humanity? To answer this question, just look around. Thanks to the discovery and study of electricity, people use artificial lighting, and their lives are made easier by countless electrical devices. Physicists' research into electrical discharges led to the discovery. It is thanks to physical research that people all over the world use the Internet and cell phones. Once upon a time, scientists were sure that vehicles heavier than air could not fly; it seemed natural and obvious. But Montgolfier, the inventors of the hot air balloon, and after them the Wright brothers, who created the first one, proved these claims to be unfounded. It is thanks to humanity that the power of steam has been put to its service. The appearance of steam engines, and with them steam locomotives and steamships, gave a powerful impetus to. Thanks to the tamed power of steam, people were able to use mechanisms in plants and factories that not only made work easier, but also increased its productivity tens, hundreds of times. Without this science, space flights would not have been possible. Thanks to Isaac Newton's discovery of the law of universal gravitation, it became possible to calculate the force required to launch a spacecraft into Earth orbit. Knowledge of the laws of celestial mechanics allows automatic interplanetary stations launched from Earth to successfully reach other planets, covering millions of kilometers and accurately reaching their intended target. It can be said without exaggeration that the knowledge acquired by physicists over centuries of scientific development is present in any area of human activity. Take a look at what surrounds you now - the achievements of physics played a crucial role in the production of all the objects around you. Nowadays, this is actively developing, a truly mysterious direction has appeared in it, like quantum physics. Discoveries made in this area can change a person's life beyond recognition.

Sources:

is physics necessary?

In the era of industrial and technological progress, philosophy has faded into the background; not every person can clearly answer the question of what kind of science it is and what it does. People are busy with pressing problems; they are of little interest in philosophical categories divorced from life. Does this mean that philosophy has lost its relevance and is no longer needed?

Philosophy is defined as a science that studies the root causes and beginnings of all things. In this sense, it is one of the most important sciences for humans, since it tries to find an answer to the question of the reason for human existence. Why does a person live, why was he given this life? The answer to this question also determines the paths that a person chooses.

Being a truly comprehensive science, philosophy includes a variety of disciplines and tries to find answers to questions that are important for human existence - is there a God, what is good and evil, questions of old age and death, the possibility of objective knowledge of reality, etc. and so on. We can say that natural sciences provide an answer to the question “how?”, while philosophy tries to find an answer to the question “why?”

It is believed that the term “philosophy” itself was coined by Pythagoras; translated from Greek it means “love of wisdom.” It should be noted that, unlike other sciences, in philosophy no one obliges anyone to base their reasoning on the experience of predecessors. Freedom, including freedom of thought, is one of the key concepts for the philosopher.

Philosophy arose independently in Ancient China, Ancient India and Ancient Greece, from where it began to spread throughout the world. The classification of currently existing philosophical disciplines and trends is quite complex and not always unambiguous. General philosophical disciplines include metaphilosophy, or philosophy of philosophy. There are philosophical disciplines that study ways of knowing: logic, theory of knowledge, philosophy of science. Theoretical philosophy includes ontology, metaphysics, philosophical anthropology, philosophy of nature, natural theology, philosophy of spirit, philosophy of consciousness, social philosophy, philosophy of history, philosophy of language. Practical philosophy, sometimes called philosophy of life (axiology), includes ethics, aesthetics, praxeology (philosophy of activity), social philosophy, geophilosophy, philosophy of religion, law, education, history, politics, economics, technology, ecology. There are other areas of philosophy; you can get acquainted with the full list by looking at specialized philosophical literature.

Despite the fact that the new century seems to leave little room for philosophy, its practical significance does not decrease in the least - humanity is still looking for answers to the questions of existence that concern it. And the answer to these questions determines which path human civilization will take in its development.

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Discipline in a broad concept is following established rules and regulations. In production, these regulations and regime restrictions are determined by an officially approved document - “Internal Regulations”. The employee becomes acquainted with them when applying for a job and, by signing an employment contract, he formally undertakes to fulfill them.

Ideally, in an enterprise where “iron” discipline is established, all employees strictly and precisely observe the order, work schedule and rules established by laws, by-laws and local acts, regulations, instructions and orders for the organization, and also strictly follow the orders of managers. It’s clear that you won’t even find such discipline now. But how necessary is it for?

The discipline is designed to ensure unity and continuity in work and technological processes, which is reflected in the quality of products produced and services provided. It is discipline that makes the production behavior of employees predictable, amenable to planning and forecasting. This allows for interaction not only at the level of ordinary performers, but also between departments of the enterprise as a whole. The efficiency of labor depends on it, and, therefore, its quantitative and qualitative indicators.

There are objective and subjective aspects of the discipline. Objective ones find expression in the system of established norms and rules that operates at the enterprise. Subjective ones represent the desire of each employee to fulfill them. The task of management is to create conditions in the company where the requirements of discipline would be placed above the interests of individual members of the workforce. In this case, there is no need to exercise control and restraining functions on the part of management - the team itself mobilizes to fight mismanagement, bureaucracy, absenteeism and other phenomena that interfere with normal work.

You should not expect employees to comply with discipline standards when the management of the enterprise itself constantly violates it, unreasonably involving them in unscheduled and emergency work, work after hours and on weekends. In this case, employees will quite rightly believe that labor discipline on a regular working day can be violated, since they work after hours. If you are a manager, then start fulfilling the requirements of discipline from yourself. Only in this case will you be able to demand this from your subordinates and avoid sabotage.

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It would seem that the fewer words in a language, the easier it is to communicate. Why “invent” such different words to denote essentially the same object or phenomenon, i.e. ? But upon careful consideration, it becomes clear that synonyms carry a number of absolutely necessary functions.

Richness of speech

In the essays of younger schoolchildren, you can often find text with approximately the following content: “The forest was very beautiful. Beautiful flowers and trees grew there. It was such beauty! This happens because the child’s vocabulary is still quite small, and he has not learned to use synonyms. In adult speech, especially written speech, such repetitions are considered a lexical error. Synonyms allow you to diversify your speech and enrich it.

Shades of meaning

Each of the synonyms, although expressing a similar meaning, gives it its own special shade of meaning. Thus, in the synonymous series “unique - amazing - impressive”, the word “amazing” means an object that primarily causes surprise, “unique” - an object that is not like the others, one of a kind, and “impressive” - making a strong impression, but this impression may be something other than simple surprise, and this object may also be similar to similar ones, i.e. not to be “unique”.

Emotionally expressive coloring of speech

The synonymous series contains words that have different expressive and emotional meanings. Thus, “eyes” is a neutral word, denoting the human organ of vision; “eyes” - a word belonging to the book style, also means eyes, but, as a rule, large and beautiful. But the word “burkaly” also means large eyes, but not distinguished by beauty, rather ugly. This word carries a negative assessment and belongs to the colloquial style. Another colloquial word “zenki” also means ugly eyes, but small in size.

Clarifying the meaning

Most borrowed words have an analogy in Russian. They can be used to clarify the meaning of terms and other special words of foreign origin that may not be clear to a wide range of readers: “Preventive measures will be taken, i.e. preventive measures"

Paradoxically, synonyms can also express opposite shades of meaning. Thus, in Pushkin’s “Eugene Onegin” the phrase “Tatyana looks and does not see” occurs, and this is not perceived as a contradiction, because “to look” is “to direct one’s gaze in a certain direction,” and “to see” is “to perceive and comprehend what appears before your eyes.” In the same way, the phrases “equal, but not the same”, “not just think, but reflect”, etc. do not cause rejection.

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Physics is a science that studies the fundamental laws of the material world, describing with the help of laws the properties and movement of matter, natural phenomena and its structure.

Science begins from then
how they begin to measure...
D. I. Mendeleev

Think about the words of a famous scientist. From them the role of measurements in any science, and especially in physics, is clear. But, in addition, measurements are important in practical life. Can you imagine your life without measuring time, mass, length, car speed, electricity consumption, etc.?

How to measure a physical quantity? Measuring instruments are used for this purpose. Some of them you already know. These are different types of rulers, watches, thermometers, scales, protractors (Fig. 20), etc.

Rice. 20

There are measuring instruments digital And scale. In digital instruments, the measurement result is determined by numbers. These are an electronic watch (Fig. 21), a thermometer (Fig. 22), an electricity meter (Fig. 23), etc.

Rice. 21

Rice. 22

Rice. 23

A ruler, a clock, a household thermometer, a scale, a protractor (see Fig. 20) are scale instruments. They have a scale. It determines the measurement result. The entire scale is lined with strokes into divisions (Fig. 24). One division is not one stroke (as students sometimes mistakenly believe). This is the space between the two nearest strokes. In Figure 25, there are two divisions between the numbers 10 and 20, and there are 3 strokes. The instruments that we will use in laboratory work are mainly scale ones.

Rice. 24

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To measure a physical quantity means to compare it with a homogeneous quantity taken as a unit.

For example, to measure the length of a straight line segment between points A and B, you need to apply a ruler and use the scale (Fig. 26) to determine how many millimeters fit between points A and B. The homogeneous value with which the length of the segment AB was compared was a length equal to 1 mm.

Rice. 26

If a physical quantity is measured directly by taking data from the instrument scale, then such a measurement is called direct.

For example, by applying a ruler to a block in different places, we will determine its length a (Fig. 27, a), width b and height c. We determined the value of length, width, height directly by taking a reading from the ruler scale. From Figure 27, b it follows: a = 28 mm. This is a direct measurement.

Rice. 27

How to determine the volume of a block?

It is necessary to carry out direct measurements of its length a, width b and height c, and then using the formula

V = a. b. c

calculate the volume of the block.

In this case, we say that the volume of the bar was determined by the formula, that is, indirectly, and the measurement of the volume is called an indirect measurement.

Rice. 28

Think and answer

Figure 28 shows several measuring instruments.
1. What are these measuring instruments called?
2. Which ones are digital?
3. What physical quantity does each device measure?
4. What is the homogeneous value on the scale of each device presented in Figure 28, with which the measured value is compared?
Resolve the dispute.
Tanya and Petya solve the problem: “Use a ruler to determine the thickness of one sheet of a book containing 300 pages. The thickness of all sheets is 3 cm.” Petya claims that this can be done by directly measuring the thickness of the sheet with a ruler. Tanya believes that determining the thickness of a sheet is an indirect measurement.
What do you think? Justify your answer.

Interesting to know!

While studying the structure of the human body and the functioning of its organs, scientists also take many measurements. It turns out that a person whose mass is approximately 70 kg has about 6 liters of blood. The human heart in a calm state contracts 60-80 times per minute. During one contraction it releases an average of 60 cm 3 of blood, about 4 liters per minute, about 6-7 tons per day, more than 2000 tons per year. So our heart is a big worker!

A person’s blood passes through the kidneys 360 times a day, purifying them of harmful substances. The total length of the renal blood vessels is 18 km. By leading a healthy lifestyle, we help our body work without failures!

Homework

Rice. 29

List in your notebook the measuring instruments that you have in your apartment (house). Sort them into groups:
1) digital; 2) scale.
Check the validity of the rule of Leonardo da Vinci (Fig. 29) - a brilliant Italian artist, mathematician, astronomer, and engineer. For this:
1. measure your height: ask someone to use a triangle (Fig. 30) to put a small line on the door frame with a pencil; measure the distance from the floor to the marked line;
2. measure the distance along a horizontal straight line between the ends of your fingers (Fig. 31);
3. compare the value obtained in point b) with your height; for most people these values are equal, which was first noted by Leonardo da Vinci.

Rice. thirty

Rice. 31

Why does a person need measurements?

Measurement is one of the most important things in modern life. But not always

it was like this. When a primitive man killed a bear in an unequal duel, he, of course, rejoiced if it turned out to be big enough. This promised a well-fed life for him and the entire tribe for a long time. But he did not drag the bear carcass to the scales: at that time there were no scales. There was no particular need for measurements when a person made a stone axe: there were no technical specifications for such axes and everything was determined by the size of a suitable stone that could be found. Everything was done by eye, as the master’s instincts suggested.

Later, people began to live in large groups. The exchange of goods began, which later turned into trade, and the first states arose. Then the need for measurements arose. The royal arctic foxes had to know the area of each peasant's field. This determined how much grain he should give to the king. It was necessary to measure the harvest from each field, and when selling flax meat, wine and other liquids, the volume of goods sold. When they started building ships, it was necessary to outline the correct dimensions in advance: otherwise the ship would have sunk. And, of course, the ancient builders of pyramids, palaces and temples could not do without measurements; they still amaze us with their proportionality and beauty.

ANCIENT RUSSIAN MEASURES.

The Russian people created their own system of measures. Monuments of the 10th century speak not only of the existence of a system of measures in Kievan Rus, but also of state supervision over their correctness. This supervision was entrusted to the clergy. One of the charters of Prince Vladimir Svyatoslavovich says:

“...from time immemorial it was established and entrusted to the bishops of the city and everywhere all sorts of measures and measures and weights... to observe without dirty tricks, neither to multiply nor to diminish...” (... it has long been established and entrusted to bishops to monitor the correctness of measures.. .do not allow them to be diminished or increased...). This need for supervision was caused by the needs of trade both within the country and with the countries of the West (Byzantium, Rome, and later German cities) and the East (Central Asia, Persia, India). Markets took place on the church square, in the church there were chests for storing agreements on trade transactions, the correct scales and measures were located at the churches, and goods were stored in the basements of the churches. The weighings were carried out in the presence of representatives of the clergy, who received a fee for this in favor of the church

Length measures

The oldest of them are cubit and fathom. We do not know the exact original length of either measure; a certain Englishman who traveled around Russia in 1554 testifies that a Russian cubit was equal to half an English yard. According to the "Trading Book" compiled for

Familiarize yourself with the structure and principle of operation of an aneroid barometer and teach how to use it.

To promote the development of the ability to connect natural phenomena with physical laws.

Continue to form ideas about atmospheric pressure and the connection between atmospheric pressure and altitude above sea level.

Continue to cultivate an attentive, friendly attitude towards participants in the educational process, personal responsibility for the implementation of collective work, an understanding of the need to take care of the cleanliness of the atmospheric air and comply with the rules of environmental protection, and the acquisition of everyday skills.

Imagine a sealed cylinder filled with air, with a piston installed on top. If you start to press on the piston, the volume of air in the cylinder will begin to decrease, air molecules will begin to collide with each other and with the piston more and more intensely, and the pressure of compressed air on the piston will increase.

If the piston is now sharply released, the compressed air will sharply push it upward. This will happen because, with a constant area of the piston, the force acting on the piston from the compressed air will increase. The area of the piston remained unchanged, but the force exerted by the gas molecules increased, and the pressure increased accordingly.

Or another example. A man stands on the ground, stands with both feet. In this position, a person is comfortable and does not experience any discomfort. But what happens if this person decides to stand on one leg? He will bend one of his legs at the knee, and will now rest on the ground with only one foot. In this position, a person will feel a certain discomfort, because the pressure on the foot has increased, approximately 2 times. Why? Because the area through which gravity now presses a person to the ground has decreased by 2 times. Here is an example of what pressure is and how easily it can be detected in everyday life.

Pressure in physics

From the point of view of physics, pressure is a physical quantity that is numerically equal to the force acting perpendicular to a surface per unit area of a given surface. Therefore, to determine the pressure at a certain point on the surface, the normal component of the force applied to the surface is divided by the area of the small surface element on which this force acts. And in order to determine the average pressure over the entire area, the normal component of the force acting on the surface must be divided by the total area of this surface.

Pascal (Pa)

Pressure is measured in the SI system in pascals (Pa). This unit of measurement of pressure got its name in honor of the French mathematician, physicist and writer Blaise Pascal, the author of the fundamental law of hydrostatics - Pascal's Law, which states that the pressure exerted on a liquid or gas is transmitted to any point without changes in all directions. The pressure unit "pascal" was first introduced into circulation in France in 1961, according to the decree on units, three centuries after the death of the scientist.

One pascal is equal to the pressure caused by a force of one newton, uniformly distributed, and directed perpendicular to a surface of one square meter.

Pascals measure not only mechanical pressure (mechanical stress), but also elastic modulus, Young's modulus, bulk modulus, yield strength, proportional limit, tensile strength, shear strength, sound pressure and osmotic pressure. Traditionally, it is in pascals that the most important mechanical characteristics of materials in strength materials are expressed.

Technical atmosphere (at), physical (atm), kilogram-force per square centimeter (kgf/cm2)

In addition to pascal, other (non-system) units are also used to measure pressure. One such unit is the “atmosphere” (at). The pressure of one atmosphere is approximately equal to the atmospheric pressure on the surface of the Earth at ocean level. Today, “atmosphere” refers to the technical atmosphere (at).

Technical atmosphere (at) is the pressure produced by one kilogram-force (kgf) distributed evenly over an area of one square centimeter. And one kilogram-force, in turn, is equal to the force of gravity acting on a body weighing one kilogram under conditions of gravitational acceleration equal to 9.80665 m/s2. One kilogram-force is thus equal to 9.80665 newton, and 1 atmosphere turns out to be equal to exactly 98066.5 Pa. 1 at = 98066.5 Pa.

For example, the pressure in car tires is measured in atmospheres; for example, the recommended tire pressure for the GAZ-2217 passenger bus is 3 atmospheres.

There is also a “physical atmosphere” (atm), defined as the pressure of a column of mercury, 760 mm high, at its base, given that the density of mercury is 13595.04 kg/m3, at a temperature of 0 ° C and under conditions of gravity acceleration equal to 9, 80665 m/s2. So it turns out that 1 atm = 1.033233 atm = 101,325 Pa.

As for kilogram-force per square centimeter (kgf/cm2), this extra-systemic unit of pressure is equal to normal atmospheric pressure with good accuracy, which is sometimes convenient for assessing various effects.

Bar (bar), barium

The off-system unit "bar" is equal to approximately one atmosphere, but is more accurate - exactly 100,000 Pa. In the CGS system, 1 bar is equal to 1,000,000 dynes/cm2. Previously, the name “bar” was given to a unit now called “barium” and equal to 0.1 Pa or in the CGS system 1 barium = 1 dyne/cm2. The word "bar", "barium" and "barometer" all come from the same Greek word for "gravity".

The unit mbar (millibar), equal to 0.001 bar, is often used to measure atmospheric pressure in meteorology. And to measure pressure on planets where the atmosphere is very rarefied - μbar (microbar), equal to 0.000001 bar. On technical pressure gauges, most often the scale is graduated in bars.

Millimeter of mercury (mmHg), millimeter of water (mmHg)

The non-system unit of measurement “millimeter of mercury” is equal to 101325/760 = 133.3223684 Pa. It is designated “mmHg”, but is sometimes denoted “torr” - in honor of the Italian physicist, Galileo’s student, Evangelista Torricelli, the author of the concept of atmospheric pressure.

The unit was formed in connection with the convenient method of measuring atmospheric pressure with a barometer, in which the mercury column is in equilibrium under the influence of atmospheric pressure. Mercury has a high density of about 13600 kg/m3 and is characterized by a low saturated vapor pressure at room temperature, which is why mercury was chosen for barometers at one time.

At sea level, the atmospheric pressure is approximately 760 mm Hg, it is this value that is now considered normal atmospheric pressure, equal to 101325 Pa or one physical atmosphere, 1 atm. That is, 1 millimeter of mercury is equal to 101325/760 pascal.

Pressure is measured in millimeters of mercury in medicine, meteorology, and aviation navigation. In medicine, blood pressure is measured in mmHg; in vacuum technology, blood pressure measuring instruments are calibrated in mmHg, along with bars. Sometimes they even simply write 25 microns, meaning microns of mercury when we are talking about evacuation, and pressure measurements are carried out with vacuum gauges.

In some cases, millimeters of water column are used, and then 13.59 mm water column = 1 mm Hg. Sometimes this is more appropriate and convenient. A millimeter of water column, like a millimeter of mercury, is a non-systemic unit, equal in turn to the hydrostatic pressure of 1 mm of a water column, which this column exerts on a flat base at a water column temperature of 4 ° C.

Comments

The problem of arterial hypertension has become one of the most pressing in modern medicine. A large number of people suffer from high blood pressure (BP). Heart attack, stroke, blindness, kidney failure - all these are formidable complications of hypertension, the result of improper treatment or its absence at all. There is only one way to avoid dangerous complications - maintaining a constant normal level of blood pressure with the help of modern high-quality medications.

The selection of medications is the responsibility of the doctor. The patient is required to understand the need for treatment, follow the doctor’s recommendations and, most importantly, constant self-monitoring.

Every patient suffering from hypertension should regularly measure and record their blood pressure and keep a diary of their well-being. This will help the doctor evaluate the effectiveness of treatment, adequately select the dose of the drug, assess the risk of possible complications and effectively prevent them.

At the same time, it is important to measure pressure and know its average daily level at home, because pressure figures obtained at a doctor’s appointment are often overestimated: the patient is worried, tired, sitting in line, forgot to take medicine and for many other reasons. And, conversely, situations may arise at home that cause a sharp increase in blood pressure: stress, physical activity, etc.

Therefore, every hypertensive person should be able to measure blood pressure at home in a calm, familiar environment in order to have an idea of the true level of pressure.

HOW TO CORRECTLY MEASURE PRESSURE?

When measuring blood pressure, you must adhere to some rules:

Measure your blood pressure in a quiet environment at a comfortable temperature, no earlier than 1 - 2 hours after eating, no earlier than 1 hour after smoking or drinking coffee. Sit comfortably against the back of a chair without crossing your legs. The arm should be bare, and the rest of the clothing should not be narrow or tight. Do not talk, this may affect the accuracy of the blood pressure measurement.

The cuff must have a length and width appropriate to the size of the hand. If the shoulder circumference exceeds 32 cm or the shoulder has a cone-shaped shape, which makes it difficult to apply the cuff correctly, a special cuff is required, because the use of a narrow or short cuff leads to a significant overestimation of blood pressure values.

Place the cuff so that its bottom edge is 2.5 cm above the edge of the cubital fossa. Do not squeeze it too tightly - your finger should fit freely between the shoulder and the cuff. Place the stethoscope where you can best hear the brachial artery pulsation just above the cubital fossa. The membrane of the stethoscope should fit snugly against the skin. But do not press too hard to avoid additional compression of the brachial artery. The stethoscope should not touch the tonometer tubes so that sounds from contact with them do not interfere with the measurement.

Place the stethoscope at the level of the subject's heart or at the level of his 4th rib. Pump air into the cuff vigorously; slow inflation increases pain and worsens the quality of sound perception. Release the air from the cuff slowly - 2 mmHg. Art. per second; The slower the air is released, the higher the quality of the measurement.

Repeated blood pressure measurement is possible 1 - 2 minutes after the air has completely left the cuff. Blood pressure can fluctuate from minute to minute, so the average of two or more measurements more accurately reflects the true intra-arterial pressure. SYSTOLIC AND DIASTOLIC PRESSURE

To determine pressure parameters, it is necessary to correctly evaluate the sounds that are heard “in a stethoscope.”

Systolic pressure is determined by the nearest scale division at which the first consecutive tones become audible. In case of severe rhythm disturbances, for accuracy it is necessary to take several measurements in a row.

Diastolic pressure is determined either by a sharp decrease in the volume of tones, or by their complete cessation. Zero pressure effect, i.e. continuous up to 0 tones, can be observed in some pathological conditions (thyrotoxicosis, heart defects), pregnancy, and in children. When diastolic pressure is above 90 mmHg. Art. it is necessary to continue measuring blood pressure for another 40 mmHg. Art. after the disappearance of the last tone, in order to avoid falsely elevated diastolic pressure values due to the phenomena of “auscultatory failure” - temporary cessation of sounds.

Often, to obtain a more accurate result, it is necessary to measure the pressure several times in a row, and sometimes to calculate the average value, which more accurately corresponds to the true intra-arterial pressure.

HOW TO MEASURE PRESSURE?

Doctors and patients use various types of tonometers to measure blood pressure. Tonometers are distinguished according to several criteria:

According to the location of the cuff: “shoulder” tonometers are in the lead - the cuff is placed on the shoulder. This position of the cuff allows you to obtain the most accurate measurement result. Numerous studies have shown that all other positions (“cuff on the wrist”, “cuff on the finger”) can produce significant discrepancies with the true pressure. The result of measurements with a wrist device is very dependent on the position of the cuff relative to the heart at the time of measurement and, most importantly, on the measurement algorithm used in a particular device. When using finger tonometers, the result may even depend on the temperature of the finger and other parameters. Such tonometers cannot be recommended for use.

Pointer or digital - depending on the type of determination of measurement results. The digital tonometer has a small screen on which pulse, pressure and some other parameters are displayed. A dial tonometer has a dial and a needle, and the measurement result is recorded by the researcher himself.

The tonometer can be mechanical, semi-automatic or fully automatic, depending on the type of air injection device and measurement method. WHICH TONOMETER TO CHOOSE?

Each tonometer has its own characteristics, advantages and disadvantages. Therefore, if you decide to buy a tonometer, pay attention to the features of each of them.

Cuff: Should fit your arm. A standard cuff is designed for a hand with a circumference of 22 - 32 cm. If you have a large hand, you need to purchase a larger cuff. Small children's cuffs are available for measuring blood pressure in children. In special cases (congenital defects), thigh pressure cuffs are required.
It is better if the cuff is made of nylon and equipped with a metal ring, which greatly facilitates the process of attaching the cuff to the shoulder when measuring pressure independently. The inner chamber must be made using seamless technology or have a special shape, which provides the cuff with strength and makes the measurement more comfortable.

Phonendoscope: Usually a phonendoscope comes with a tonometer. Pay attention to its quality. For home blood pressure measurements, it is convenient when the tonometer is equipped with a built-in phonendoscope. This is a great convenience, since in this case the phonendoscope does not need to be held in your hands. In addition, there is no need to worry about its correct location, which can be a serious problem when measuring independently and lacking sufficient experience.

Pressure gauge: a pressure gauge for a mechanical tonometer should have bright, clear divisions, sometimes they are even luminous, which is convenient when measuring in a dark room or at night. It is better if the pressure gauge is equipped with a metal case; such a pressure gauge is more durable.

It is very convenient when the pressure gauge is combined with a bulb - an air injection element. This facilitates the process of measuring pressure, allows the pressure gauge to be positioned correctly relative to the patient, and increases the accuracy of the result obtained.

Pear: as mentioned above, it is good if the bulb is combined with a pressure gauge. A high-quality bulb is equipped with a metal screw. In addition, if you are left-handed, please note that pears are adapted for use with the right or left hand.

Display: When choosing a tonometer, the size of the display matters. There are small displays where only one parameter is displayed - for example, the last blood pressure measurement. On the large display you can see the result of measuring pressure and pulse, a color pressure scale, the average pressure value from the last few measurements, an arrhythmia indicator, and a battery charge indicator.

Additional functions: the automatic blood pressure monitor can be equipped with such convenient functions as:
arrhythmia indicator - if the heart rhythm is abnormal, you will see a mark on the display or hear a sound signal. The presence of arrhythmia distorts the correct determination of blood pressure, especially with a single measurement. In this case, it is recommended to measure the pressure several times and determine the average value. Special algorithms of some devices allow accurate measurements to be made despite rhythm disturbances;
memory for the last few measurements. Depending on the type of tonometer, it may have the function of storing the last several measurements from 1 to 90. You can view your data, find out the latest pressure numbers, create a pressure graph, calculate the average value;
automatic calculation of average pressure; sound notification;
function of accelerated pressure measurement without loss of measurement accuracy; there are family models in which separate functional buttons provide the ability for two people to use the tonometer independently, with separate memory for the last measurements;
convenient models that provide the ability to operate both from batteries and from a general electrical network. At home, this not only increases the convenience of measurement, but also reduces the cost of using the device;
There are models of tonometers equipped with a printer for printing the latest blood pressure readings from memory, as well as devices compatible with a computer.

Thus, a mechanical tonometer provides higher quality measurements in experienced hands, in a researcher with good hearing and vision, who is able to correctly and accurately follow all the rules for measuring blood pressure. In addition, a mechanical tonometer is significantly cheaper.

An electronic (automatic or semi-automatic) tonometer is good for home blood pressure measurement and can be recommended for people who do not have the skills to measure blood pressure by auscultation, as well as for patients with reduced hearing, vision, or reaction, because does not require the measurer to directly participate in the measurement. It is impossible not to appreciate the usefulness of such functions as automatic air inflation, accelerated measurement, memory of measurement results, calculation of average blood pressure, arrhythmia indicator and special cuffs that eliminate pain during measurement.

However, the accuracy of electronic tonometers is not always the same. Preference should be given to clinically proven devices, i.e. those that have been tested according to world-renowned protocols (BHS, AAMI, International Protocol).

Sources Magazine “CONSUMER. Expertise and Tests", 38’2004, Maria Sasonko apteka.potrebitel.ru/data/7/67/54.shtml