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Pressure measuring instruments presentation. Instruments for measuring pressure. Electrical contact pressure gauges DM2005 signaling pressure gauge, explosion-proof

Instruments for measuring atmospheric pressure

Physics Presentation

7th grade

Sharonova S.M.


Pressure - This physical quantity, showing effective force per unit surface area perpendicular to that surface. Pressure is defined as P = F / S, where P is pressure, F is pressure force, S is surface area. From this formula it is clear that pressure depends on the surface area of ​​the body acting with a certain force. The smaller the surface area, the more pressure.

The unit of measurement for pressure is newton per square meter(H/m2). We can also convert pressure units N/m2 to pascals, a unit of measurement named after the French scientist Blaise Pascal, who developed the so-called Pascal's Law.

1 N/m2 = 1 Pa.


Torricelli. His mercury tube was the first barometer.

The cup barometer is an improved version of the Torricelli barometer.

For scientific and everyday purposes, you need to be able to measure atmospheric pressure. For this there are special devices- barometers. The very first device for measuring atmospheric pressure was invented...


No matter what size cup of mercury you take, no matter what diameter the tube is, the mercury will always rise to the same height - 760 mm. The barometric tube can be given different shape, only one thing is important, one end of the tube must be closed so that there is no air from above.

You can fill the tube with any liquid other than mercury, but you must remember to change its length.

Water barometers were built by Pascal (Rouen, 1646) ...

... and Otto von Guericke (Magdeburg, 1660)


The largest water barometer, 12 m high, was constructed in 1987 by Bert Bolle, curator of the Barometer Museum in Martensdijk, the Netherlands, where it is installed.

Mercury barometers provide accurate readings but require great care when handling them. The modern barometer is made liquidless!


It's called an aneroid barometer. Metal barometers are less accurate, but not as bulky or fragile.

Internal structure of an aneroid.


This barometer is called a barometric altimeter or altimeter.

An aneroid barometer is a very sensitive instrument. For example, going up to the top floor of 9 storey building, due to the difference in atmospheric pressure on different heights we will detect a decrease in atmospheric pressure of 2-3 mmHg. Art.

A barometer can be used to determine the flight altitude of an aircraft.


The idea of ​​Pascal's experiment formed the basis for the design of the altimeter. It determines the altitude above sea level by changes in atmospheric pressure.

When observing the weather in meteorology, if it is necessary to record fluctuations in atmospheric pressure over a certain period of time, they use recorder- barograph.



To measure pressure, different units are used: mm of mercury, physical atmospheres,

in the SI system

Pascals.

All living organisms are adapted to live at certain values ​​of atmospheric pressure. Humans and most animals do not tolerate high altitude conditions well, but some birds reach significant heights in flight. The condor bird can rise to a height of up to 9000m, mountain jackdaws - up to 8200m, vultures and hawks - up to 6000-7000m, eagle - up to 5000m, other birds stay at an altitude of no more than 4000m.


The largest water barometer, 12 m high, was constructed in 1987 by Bert Bolle, curator of the Barometer Museum in Martensdijk, the Netherlands, where it is installed.

Can a person produce a pressure of 1000 atm? Yes, by sticking a needle into the fabric!

Remember the experience of Otto von Guericke - 1654 in the city of Magdeburg. It turns out that " Magdeburg hemispheres“every person has: the heads of the femurs are held in the pelvic joint by atmospheric pressure.

How can a driver help a friend and pour gasoline from his car into the gas tank of another? There is such a simple device - a siphon. Its work is based on the action of atmospheric pressure.

The structure of the Earth's atmosphere resembles a multi-story building.


  • The first “floor” is the troposphere: up to 11 km high at sea level, it contains 4/5 of the mass of all air, the temperature drops with height, and clouds form here.
  • The second “floor” is the stratosphere: up to 55 km above sea level, contains 1/5 of all air, the kingdom of cold with a temperature of about minus 40 degrees Celsius, the ozone layer is located here.
  • The third “floor” is the mesosphere: up to 200 km above sea level, the air is very rarefied, the pressure is 1/25000 of normal atmospheric pressure.
  • The fourth “floor” is the thermosphere: unprecedented heat of about 1000-2000 degrees Celsius, air density is extremely low, falling meteors ignite here.
  • The fifth “floor” is the exosphere: the outer shell of the atmosphere, up to 600 km high, the strongest air rarefaction; even higher, signs of air particles can be traced to an altitude of more than 1000 km.


ABOUT STRANGE FISH - STICKED

This fish sticks to the shark with such force that it is impossible to tear it off. This live hook is still used in Australia to catch sharks and large fish, and in South America– turtles. With the help of stick fish, fish weighing up to 18 kg are caught. There are metal vacuum lifting devices. These suction cups are metal or rubber bowls similar to Magndeburg hemispheres with a diameter of 50 to 600 mm; they can lift loads weighing up to 700 kg. By attaching several suction cups to an object, you can lift a load weighing up to 10 tons!

IN Lately in medicine they began to use a “liquid scalpel”, i.e. tissue incision during surgery is carried out with a thin stream of saline solution under a pressure of about 120 atmospheres.


LET'S THINK ABOUT "5"?

1. What is the difference between the change in air density with height and the density of water at different sea depths? 2. Which barometer is more sensitive: mercury or oil? Why? 3. Is it possible to measure the pressure on board? space station a mercury barometer, or an aneroid?

4. What type of barometer should be used to measure internal pressure spaceship when it is moving with the engine off? Why?


  • Option 7-3-1
  • 1. Determine the area of ​​one tractor caterpillar, which, with a mass of 3880 kg, exerts a pressure on the ground of 4 N/sq.cm? 2. For a smaller piston hydraulic machine area 5 sq.cm. a force of 2500 N acts. What load is lifted by the machine with a large piston whose area is 200 sq.cm? 3. What pressure does a layer of kerosene 0.6 meters high exert on the bottom of the vessel? 4. With what force does the air press on a table with an area of ​​0.7 square meters? Why do we not experience the action of this force when we lift the table? 5. Water is poured into one elbow of communicating vessels to a height of 10 cm; to what height should mercury be poured into the other elbow in order to achieve equilibrium of the liquids in the vessel’s elbows?
  • Everyone decides their own option

Option 7-3-2.

1. What pressure does it exert on the ground? Brick wall 2.5 meters high?

2. The pump pumps oil into Hydraulic Press under pressure 30 N/sq.cm. With what force does the press compress the pressed part if the area of ​​the press piston is 0.08 sq.m.?

H. The tank with kerosene has a side hole, closed with a plug with an area of ​​8 sq. cm. What force must keep the plug from flying out if the hole is at a depth of 1.8 meters?

4. Determine with what force the atmosphere presses on window glass area 1.5 sq.m. Why doesn’t the glass shatter into pieces from such terrible force?

5. Water is poured into one elbow of communicating vessels to a height

6 cm. To what height should you pour kerosene into the other elbow to achieve equilibrium of liquids in the legs of the vessel?

Option 7-3-3.

1. A tractor having a support area of ​​two tracks of 2.4 sq.m. produces a pressure on the ground equal to 5 N/cm2. Determine the mass of the tractor.

2. The area of ​​small piston of hydraulic machine is 10 times less area second piston. What force must be applied to the large piston to keep a 1 kg load on the small piston in balance?

3. The pipe can withstand pressure of 500,000 N/sq.m. To what height can water be supplied through this pipe?

4. With what force does the atmosphere press on a person whose skin surface area is 2 square meters? Why does a person not notice the effect of this force on himself?

5. In communicating vessels of the same shape there are 10 cubic meters. cm of water and 10 cc. kerosene. What is the difference in fluid levels in the right and left vessels?

Option 7-3-4.

1. Find the area of ​​the piston, which, under pressure on it compressed air 48 N/sq.cm. develops a force of 120,000 N.

2. A cubic vessel with a volume of 1 cubic meter. filled with water. Determine the pressure at the bottom of the vessel.

H. In a cylinder under a piston with an area of ​​0.1 sq.m. there are 9 kg of water. What is the pressure on the bottom of the cylinder if a 1 kg weight is placed on the piston in stages?

4. Air pressure at an altitude of 10 km is 26000 Pa. With what force does the air in an airplane squeeze out a window glass with an area of ​​800 sq. cm?

5. There are 10 cubic cm in communicating vessels of the same shape. water and 3 cc. mercury What is the difference in fluid levels in the right and left vessels?

Option 7-3-5.

1. What should be the area of ​​the skis so that a person weighing 70 kg exerts a pressure of no more than 0.5 N/cm2 on the snow?

2. Hydraulic machine piston with an area of ​​2 cm2. is lowered by a force of 150 N. What is the weight of the load lifted by the second piston of area 8 cm2?

H. The fountain's water rises to a height of 5 m. What is the water pressure in the pipe supplying water to the fountain?

4. What force of atmospheric pressure acts on a notebook sheet with an area of ​​350 sq. cm? Why doesn't this sheet tear under the influence of such enormous force?

5. On one side of the communicating vessels, water was poured to a height of 4 cm, and on the other, an unknown liquid was poured, which needed to be poured to a height of 5 cm before reaching equilibrium in the communicating vessels. What kind of liquid is this?


Answers

task\option

7 - 3 - 1

7 - 3 - 2

7 - 3 - 3

7 - 3 - 4

7 - 3 - 5

density 800 kg/m 3, most likely it is kerosene


Atmospheric Barometer – a physical instrument for measuring atmospheric pressure. Normal atmospheric pressure is the pressure that is balanced by a column of mercury 760 mm high at a temperature of 0 °C. deterioration A decrease in atmospheric pressure portends worsening weather. 12 m As you rise above the Earth's surface, atmospheric pressure decreases by approximately 1 mm Hg. Art. for every 12 m of rise. decreaseThe decrease in pressure is accompanied by a decrease in the density of the atmosphere, and it gradually moves into outer space. 3




5 Liquid pressure gauge 1 – double-jointed glass tube 2 – rubber tube 3 – round flat box covered with rubber film Action of liquid U- shaped pressure gauges based on comparing the pressure in a closed knee with the external pressure in an open one.




7 Tubular pressure gauge 1 - tube 2 - arrow 3 - gears 4 - inlet valve 5 - lever 3 In a tubular pressure gauge, the pointer arrow is connected to a tube bent in the shape of an arc. As the pressure inside the tube increases, it straightens and the pointer arrow rotates.


The most common are pressure gauges with tubular spring. If you create pressure in a curved tube, the cross-section of which is shown in Figure 11, then such a tube will bend by an amount proportional to the pressure. The end of the tube, moving, will pull rack and will rotate the axis on which the arrow is mounted. Such pressure gauges are used up to 1016 thousand atmospheres.




10 Pressure gauge with Bourdon tubular spring are designed for measuring pressure of non-aggressive copper alloys (ammonia, alkali and saline solutions), non-crystallizing media of liquids, gas and steam. 1 bar = Pa (pascals) There are two well-known units for measuring pressure - psi and bar. While psi is still used in the US, the metric unit bar is the generally accepted one. Bar is often replaced by pascals and kilopascals because these units are more convenient. There are many other units of measurement, but they are used in highly specialized areas. 1 psi (1 pound per square inch) = Pa 1 pound per square inch. inch = Pa 1 atmosphere = Pa


11 Use of pressure gauges Measuring blood pressureblood pressure Checking tire pressure Measuring pressure in the fuel system of carscars Measuring pressure in a gas welding cylinder gas welding Monitoring the pressure in a scuba tank scuba tank Measuring pressure and vacuum diesel fuel, water, gases and water vapor, oxygen, freons on ships. on ships. Control of foam pressure in pumped portable fire extinguishers Fire extinguishers Control of pressure in power and brake systems and installations of rolling stock Measuring and adjusting the compressed air pressure of a spray gun. Heating system pressure control






14 Pressure regulator with pressure gauge is designed for precise measurement and adjusting the compressed air pressure at the spray gun inlet. 1 bar = pascals (Pa) 1 psi = Pa




16 Pressure gauge for checking tire pressure 1 atmosphere = Pa








24 The cylinder pressure indicator, as well as the depth gauge, uses the Bourdon tube principle. The pressure gauge readings should be clearly visible under all conditions. The pressure gauge is connected to the first stage gearbox from the side high pressure. Pressure gauge, depth gauge and compass


26 A pressure gauge is a physical device for measuring pressure inside closed vessels. Typically, a pressure gauge measures the difference between the pressure in a vessel and atmospheric pressure. The pressure of a gas in a closed container increases as the density or temperature of the gas increases. The state of gas at low pressure is called vacuum. Conclusions:


Presentation on the topic "Pressure gauges" in physics in powerpoint format. The purpose of this presentation for 7th grade schoolchildren is to give an idea of ​​the structure and operating principles of liquid and metal pressure gauges, and to consider their use in various fields. Author of the presentation: physics teacher, Marianna Sergeevna Gagarina.

Fragments from the presentation

Test

  1. Which scientist proposed a way to measure atmospheric pressure?
  2. What letter represents atmospheric pressure?
  3. What is the unit of atmospheric pressure?
  4. What is the name of the device for measuring atmospheric pressure?
  5. What is the value of normal atmospheric pressure?
  6. What is the name of the altitude measuring device used in aviation?

Pressure gauges– instruments for measuring pressures greater or less than atmospheric pressure (from the Greek “manos” - rare, loose and “metreo” - I measure.

Pressure gauges are:
  • liquid
  • metal

Liquid pressure gauge

  • A liquid pressure gauge consists of a two-legged glass tube into which some liquid is poured.
  • Design and principle of operation of an open liquid pressure gauge

Metal pressure gauge device

  • Metal tube bent into an arc
  • Lever arm
  • Toothwort
  • Arrow

Pressure gauges are used in all cases where it is necessary to know, control and regulate pressure. Most often, pressure gauges are used in heat power engineering, chemical and petrochemical enterprises, and food industry enterprises.

Sphygmomanometer (tonometer)- measuring device blood pressure. It consists of a cuff that is placed on the patient's arm, a device for inflating air into the cuff, and a pressure gauge that measures the air pressure in the cuff. Also, the sphygmomanometer is equipped with either a stethoscope or electronic device, registering air pulsations in the cuff.

Consolidation

  • What devices did we meet today?
  • Why are the fluid levels in both elbows the same in an open pressure gauge?
  • Why do the liquid levels in the pressure gauge elbows change when the box is immersed in water?
  • How can you use a liquid pressure gauge to show that at the same depth the pressure is the same in all directions?
  • How does a metal pressure gauge work?
  • In what units is the scale of a metal pressure gauge calibrated?

Class: 7

Goals: Introduction to the operation and design of aneroid barometer and pressure gauges.

Lesson objectives:

  1. Educational:
    • Deeper study of the subject based on modern technologies and visibility.
    • Familiarity with instruments for measuring pressure, the structure, operating principle of these devices and their use in life.
    • Strengthening the understanding of the fact that atmospheric pressure decreases with altitude.
  2. Educational: The ability to listen to each other and adequately evaluate answers.
  3. Educational:
    • Development of skills to generalize and draw conclusions.
    • Development of the skill of independent search for knowledge and its practical application.

Lesson equipment.

  • Multimedia computer with PowerPoint.
  • Presentation “Aneroid barometer and pressure gauges” Appendix.
  • Instruments: aneroid barometer, liquid and metal pressure gauges.

To create presentations, we used textbook materials and information obtained on the Internet on the website www.fizika.ru, in particular, there were pictures taken and inserted into the presentation.

During the classes

1. Organizational moment.

2. Stage: repetition.

Teacher: Hello guys!

Today we have a presentation lesson. In previous lessons, you were convinced that atmospheric pressure exists, and you learned that atmospheric pressure can be measured using a device invented by the Italian scientist Evangelista Torricelli.

3. Stage: Aneroid barometer.

And now we will find out how the aneroid barometer works.

What is an aneroid barometer and what is it intended for?

In practice, an aneroid barometer is used to measure atmospheric pressure. It is called liquid-free because it does not contain mercury.

Now let’s find out how this device works.

  1. frame
  2. corrugated box
  3. glass
  4. scale
  5. spring plate
  6. arrow

Open the textbook on page 105 and read about the device.

Now look at the side view and try to name the parts of the device.

Student:

  • metal box with a wavy surface.
  • Spring.
  • Transmission mechanism
  • Pointer arrow.

Will the barometer show the same pressure on the first and second floors of our school?

Student: The pressure on the first floor will be higher than on the second floor.

Teacher: Why do you think?

Student: With altitude, pressure decreases.

For every 12 m rise, the pressure decreases by 1 mmHg. Art. Therefore, they can be called altimeters.

Teacher: What pressure do we consider normal? And what does it equal?

Student: Atmosphere pressure, equal to the pressure of a column of mercury 760 mm high at a temperature of 0°C, is callednormal atmospheric pressure. Normal atmospheric pressure is 101,300 Pa=1013 hPa.

Teacher: Guys, look at the scale of the aneroid barometer. State the measuring limit of the device.

Student: 720mmHg. – 780mmHg

Teacher: What is the division price of the device?

Student: 1mmHg.

Teacher: Close your eyes, listen to me and imagine what I will talk about. I will ask you riddles, the one who knows the answer will tell you the answer.

First - shine
Behind the shine is a crackling sound,
Behind the crackling is a splash.
(Lightning, thunder, rain)

Fluffy cotton wool
Floating somewhere.
The lower the wool,
The closer the rain comes.
(Cloud)

Colored rocker
Hanging over the forest.
(Rainbow)

White smoke pulled at the forelock,
The oak tree shook on the field.
He knocked on the gate.
Hey, open up! Who's there?
(Wind)

Flies - is silent,
Lying down - silent.
When he dies, then he will roar.
(Snow)

He will tell everyone
Although without a tongue,
When it's clear
And when there are clouds.
(Barometer)

Teacher: What do these riddles have in common?

Student: We are talking about atmospheric phenomena.

Teacher: Everything that was discussed in the riddles exists on earth only because the earth has an atmosphere. But in solar system not all planets have an atmosphere.

Space painted in black color,
Because there is no atmosphere
There is neither night nor day,
There is no earthly blue here,
The views here are strange and wonderful,
And the stars are all visible at once,
Both the Sun and the Moon.
V. P. Lepilov, Astrakhan.

4. Stage: Pressure gauges.

Teacher: Let's move on to the second part of the lesson. Pressure gauges.

Pressure gauges are used to measure pressures greater or less than atmospheric pressure.

There are 2 types of pressure gauges: liquid and metal. Let's consider the device of a liquid pressure gauge.

  • Double bend glass tube.
  • Rubber tube.
  • Scale.

Operating principle of a liquid pressure gauge.

The deeper the box is immersed in the liquid, the greater the difference in the heights of the liquid columns in the pressure gauge elbows becomes, and, consequently, the greater the pressure produced by the liquid.

Teacher: Open your textbook to page 109 and read about the construction of a metal pressure gauge. And tell us the principle of its operation.

Student: As the pressure increases, the tube straightens.

When the pressure decreases, the tube, due to its elasticity, returns to previous position, and the arrow goes to zero division scales.

5. Stage – Consolidation.

Teacher: A Now let's check how you have mastered the topic. Prepare pieces of paper, sign and number them from 1 to 10. Write only the end of the sentence.

Conceptual dictation.

1. A metal barometer, translated from Greek as liquid-free, is called.... ...aneroid

  1. The number 2 in the figure indicates... corrugated box
  2. The number 4 in the figure indicates... scale
  3. Atmospheric pressure equal to the pressure of a column of mercury 760 mm high at a temperature of 0°C is called... normal
  4. Atmospheric pressure decreases by 1 mm for each rise... 12 m
  5. A device for measuring pressures greater or less than atmospheric pressure is called... pressure gauge
  6. In the vessel in Figure B the pressure is ... atmospheric less
  7. The pressure gauge in the figure is called... metal
  8. Number 1 in the figure indicates... Metal tube
  9. The number 3 in the figure indicates... arrow

At the end of the lesson, the pieces of paper are collected and a self-test is carried out using ready-made answers on the screen. Who answered 5? At 4?

6. Stage – Lesson summary.

Teacher: So, guys, we got acquainted with devices for measuring pressure. Name these devices?

Student: Barometer and pressure gauge.

Teacher: Choose two of the 4 proposed words that relate to barometers.

Student: Aneroid and Torricelli

Teacher: . Which one do you think is more convenient to use? Why?

Student: Barometer- aneroid.

Teacher: What pressure gauges do you know?

Student: Liquid and metallic.

Teacher: Which one is more practical to use? Why? Where in your life have you seen the use of pressure gauges?

Student: Measuring pressure when filling gas cylinders in the press.

This concludes the lesson. Thank you everyone for your work, everyone who answered correctly today will receive a grade - excellent, the rest of the grades will be clarified after checking the dictation.

Pressure gauge

A pressure gauge is a device that measures the pressure of a liquid or gas.

Principle of operation

The principle of operation of the pressure gauge is based on balancing the measured pressure by the force of elastic deformation of a tubular spring or a more sensitive two-plate membrane, one end of which is sealed in a holder, and the other is connected through a rod to a tribic-sector mechanism that converts the linear movement of the elastic sensing element into a circular movement of the indicating arrow. .

Types of pressure gauges

Depending on the design and sensitivity of the element, there are liquid, deadweight, and deformation pressure gauges (with a tubular spring or membrane). Pressure gauges are divided into accuracy classes: 0.15; 0.25; 0.4; 0.6; 1.0; 1.5; 2.5; 4.0 (than less number, the more accurate the device).

Types of pressure gauges

By purpose, pressure gauges can be divided into technical - general technical, electrical contact, special, recorder, railway, vibration-resistant (glycerin-filled), ship and reference (analog). General technical: designed for measuring liquids, gases and vapors that are not aggressive to copper alloys. Electrical contact: the design has special groups of electrical contacts (usually 2). One group of contacts corresponds to the minimum set pressure, the second group - to the maximum. Task values ​​may vary service personnel. The minimum pressure group can be included in electrical circuit position control or minimum pressure alarm. The same is true for the maximum pressure group. In some cases, both groups may be involved. Both the minimum and maximum groups can be set to the minimum or maximum (respectively) value of the pressure gauge scale and not be used. Electrical contact pressure gauges, as a rule, should not be used as instruments for taking readings due to the fact that the indicating arrow, when mechanically interacting with one of the contact groups, may not accurately indicate the pressure value - a noticeable error arises. A particularly popular device in this group can be called EKM 1U, although it has long been discontinued. To work in conditions of possible contamination with flammable gases, it is necessary to use explosion-proof electric contact pressure gauges. Special: oxygen - must be degreased, since sometimes even slight contamination of the mechanism in contact with pure oxygen can lead to an explosion. Often available in cases blue color with the designation on the dial O2 (oxygen); acetylene - copper alloys are not allowed in the manufacture of the measuring mechanism, since upon contact with acetylene there is a danger of the formation of explosive acetylene copper; ammonia - must be corrosion-resistant.

Reference: having a higher accuracy class (0.15; 0.25; 0.4), these devices are used to test other pressure gauges. In most cases, such devices are installed on deadweight piston pressure gauges or some other installations capable of developing the required pressure. Ship pressure gauges are intended for use in river and marine fleets. Railway: intended for use in railway transport. Self-recording: pressure gauges in a housing, with a mechanism that allows you to reproduce the operating graph of the pressure gauge on chart paper.

Application of pressure gauges Pressure gauges are used in all cases where it is necessary to know, control and regulate pressure. Most often, pressure gauges are used in heat power engineering, chemical and petrochemical enterprises, and food industry enterprises.