Presentation on the topic "pressure gauge". Pressure Gauges Piston Liquid Pump

Slide 1

Slide 2

* Atmosphere (Greek “atmos” - steam, air and “sphere” - ball) is the air shell surrounding the Earth. The atmosphere extends to a height of several thousand kilometers from the Earth's surface. The surface of the Earth is the bottom of the ocean of air. The surface of the Earth and all bodies on it experience pressure from the entire thickness of air. This pressure is called atmospheric pressure.

Slide 3

* Proof of existence atmospheric pressure. The existence of atmospheric pressure can explain many phenomena that we encounter in life. Let's look at some of them. The figure shows a glass tube, inside of which there is a piston that fits tightly to the walls of the tube. The end of the tube is lowered into the water. If you lift the piston, then water will rise behind it. This happens because when the piston rises, an airless space is formed between it and the water. Water rises into this space under pressure from outside air following the piston.

Slide 4

* In 1654, Otto Guericke in the city of Magdeburg, in order to prove the existence of atmospheric pressure, performed such an experiment. He pumped the air out of the cavity between the two metal hemispheres folded together. The pressure of the atmosphere pressed the hemispheres so tightly against each other that eight pairs of horses could not tear them apart.

Slide 5

*Torricelli experience. Atmospheric pressure was first measured by the Italian scientist Evangelista Torricelli in the experiment that bears his name. The pressure of a column of mercury 1 mm high is equal to: 1 mm Hg = 133.3 Pa 1 hPa (hectopascal) = 100 Pa.

Slide 6

* Torricelli noticed that the height of the mercury column in the tube changes, and these changes in atmospheric pressure are somehow related to the weather. If you attach a vertical scale to a tube of mercury, you get the simplest mercury barometer (Greek “baros” - heaviness, “metreo” - measure) - a device for measuring atmospheric pressure. Conclusion:

Slide 7

* Students write in their notebook: The unit of atmospheric pressure is 1 mm Hg. Art. Relationship between Pa and mm. Hg P= ρgh = 13,600 kg/m3 9.8 N/kg 0.001 m = 133.3 Pa 1 kPa = 1000 Pa 1 hPa = 100 Pa 760 mmHg ≈ 101 300 Pa ≈ 1013 hPa Units of atmospheric pressure.

Slide 8

Atmospheric pressure in wildlife Flies and tree frogs can stay on window glass thanks to tiny suction cups in which a vacuum is created and atmospheric pressure holds the suction cup on the glass. Sticky fish have a suction surface consisting of a series of folds that form deep “pockets.” When you try to tear the suction cup away from the surface to which it is stuck, the depth of the pockets increases, the pressure in them decreases, and then the external pressure presses the suction cup even harder. *

Slide 9

* The elephant uses atmospheric pressure whenever it wants to drink. His neck is short, and he cannot bend his head into the water, but only lowers his trunk and draws in air. Under the influence of atmospheric pressure, the trunk fills with water, then the elephant bends it and pours water into its mouth. The suction effect of the swamp is explained by the fact that when you raise your leg, a rarefied space is formed under it. The excess of atmospheric pressure in this case can reach 1000 N/per foot area of an adult. However, the hooves of artiodactyl animals, when pulled out of a quagmire, allow air to pass through their incision into the resulting rarefied space. The pressure from above and below the hoof is equalized, and the leg is removed without much difficulty.

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 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.

Class: 7

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

Lesson objectives:

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.
Educational: The ability to listen to each other and adequately evaluate answers.
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.

frame
corrugated box
glass
scale
spring plate
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: Atmospheric 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 more pressure produces 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

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

Slide 2

What is a pressure gauge

Pressure gauge (from Greek word“manos” - rare, loose, rarefied and “metreo” - measuring) - a device that measures pressure greater or less than atmospheric pressure.

Slide 3

What types of pressure gauges are there?

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 (the lower the number, the more accurate the device).

Slide 4

Types of pressure gauges

Slide 5

Accuracy classes

Accuracy class is the main metrological characteristic of a device, which determines the permissible values of the main and additional errors, affecting the measurement accuracy.
For pointer instruments, it is customary to indicate the accuracy class, written in the form of a number.

Slide 6

General technical pressure gauge

Designed for measuring liquids, gases and vapors that are not aggressive to copper alloys.

Slide 7

Electric contact pressure gauge

They have the ability to adjust the measured medium due to the presence of an electric contact mechanism.

Slide 8

Types of special pressure gauges

oxygen;
acetylenic;
ammonia.

Slide 9

Special oxygen pressure gauge

Oxygen ones must be degreased, since sometimes even slight contamination of the mechanism upon contact with pure oxygen can lead to an explosion. They are often produced in blue cases with the symbol O2 (oxygen) on the dial.

Slide 10

Special acetylene pressure gauge

Acetylene does not allow copper alloys in the manufacture of the measuring mechanism, since upon contact with acetylene there is a danger of the formation of explosive acetylene copper.

Slide 11

Special ammonia pressure gauge

Ammonia must be corrosion-resistant.

Slide 12

Recording pressure gauge

Pressure gauges in a housing, with a mechanism that allows you to reproduce the operating graph of the pressure gauge on chart paper.

Slide 13

How does a liquid pressure gauge work?

To understand how a pressure gauge works, it can be connected by a rubber tube to a round flat box, one side of which is covered with rubber film. If you lightly press the film with your finger, the liquid level in the pressure gauge elbow connected to the box will decrease, and in the other elbow it will increase.

Slide 14

What parts does the pressure gauge consist of?

A pressure gauge consists of a two-legged glass tube into which some liquid is poured. The liquid is installed in both elbows at the same level, since only atmospheric pressure acts on its surface in the vessel elbows.

Slide 15

Pressure gauge value

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

Slide 16

Test based on presentation material

What does a pressure gauge measure?
What kind of pressure gauge does not exist?
What does a general technical pressure gauge measure?
What are devices for measuring pressures greater or less than atmospheric pressure called?
How many elbows are there in a pressure gauge?

Municipal autonomous educational institution

"Lyceum No. 7" Berdsk

Pressure gauges Piston liquid pump Hydraulic Press

7th grade

Physics teacher I.V.Toropchina

Pressure gauges

To measure more or less

atmospheric pressure is used pressure gauges

(from Greek "manos" - loose, "metreo" - I measure).

There are pressure gauges liquid and metal .

Liquid pressure gauge

The liquid pressure gauge consists of a double-bend glass tube,

into which some liquid is poured. With flexible

tubes, one of the pressure gauge elbows is connected to a round flat

a box covered with rubber film.

Liquid pressure gauge

The operation of the pressure gauge is based on comparing the pressure in a closed

knee with external pressure in the open knee. The deeper

immerse the box in liquid, the larger it becomes

the difference in the heights of the liquid columns in the pressure gauge elbows, and thus

more pressure is produced by the liquid.

Metal pressure gauge

Using a metal pressure gauge

measure blood pressure compressed air and other gases.

1.A metal tube bent into an arc

2. Arrow

3.Zubchatka

4. Crane

5. Lever

Metal pressure gauge device

The end of the tube communicates with the help of tap 4 with the vessel in which the pressure is measured.

As the pressure increases, the tube

unbends. Closed movement

its end using lever 5 and

teeth 3 are transmitted to the arrow

2, moving near the instrument scale.

When the pressure decreases, the tube

(due to its elasticity)

returns to its original position, and

arrow - to zero division

scales.

Application of pressure gauges

Pressure gauges are used in all cases where

need to know, control and regulate

pressure. Most often, pressure gauges are used in

thermal power engineering, chemical, petrochemical

enterprises, food industry enterprises.

Pressure gauge for measurement blood pressure called: tonometer

Piston Liquid Pump

The action of piston liquid pumps is based

on the fact that under the influence of atmospheric pressure

the water in the tube rises behind the piston .

Piston liquid pump design

1 – piston 2 – 2 – valves

Pump operating principle

When the piston moves up water, under the influence of atmospheric pressure, enters the pipe, lifts the lower valve and moves behind the piston. When the piston moves down The water under the piston presses on the bottom valve and it closes.

Pump operating principle

At the same time, under water pressure, the valve inside opens

piston, and water passes into the space above the piston. At

subsequent upward movement of the piston, the

the water above it, which is poured into the barrel. Behind the piston

a new portion of water rises, which upon subsequent lowering of the piston

will be above him, etc.

How does it work piston pump with an air chamber?

1-piston

2-suction valve

3-discharge valve

4-air chamber

5-handle

Mechanisms that operate using some kind of liquid are called hydraulic (Greek “hydro” - water, liquid).

Main part hydraulic machine There are two cylinders of different diameters, equipped with pistons and connected by a tube.
The space under the pistons and the tube are filled with liquid (usually mineral oil).
The heights of the liquid columns in both cylinders are the same as long as no forces act on the pistons.

Hydraulic machine formula

Let us denote the forces acting on the pistons - F 1 And F 2 , piston areas - S 1 And S 2 .

Then the pressure under the small piston is: p 1 = F 1 S 1 , and under the big one: p 2 = F 2 S 2 .
According to Pascal's law, pressure is transmitted equally in all directions by a fluid, therefore p 1 = p 2 Substituting the corresponding values, we get