Dictionary of measuring instruments. What can be measured with a multimeter Which can be measured

It's hard to believe, but the height of the tree was determined using a very long measuring tape; however, there are much more simple methods determining the height of trees. Although these methods do not always measure height to the nearest centimeter (or inch), they are quite reliable and can measure any type of height. tall objects, such as telegraph poles, buildings, and even a magical tree grown from a bean seed: any object can be measured as long as its top is visible.

Steps

Using a Sheet of Paper

This method allows you to find the height of a tree without resorting to mathematical calculations. All you need is a piece of paper and a measuring tape. No calculations required; however, if you want to know how this method works, you will need a little knowledge of basic trigonometry.

• The section "Using a Clinometer or Theodolite" provides all the mathematical calculations and explanations, but they are not necessary to find the height of a tree using this method.

1. Fold a piece of paper diagonally to form a triangle. If the sheet is not square, but rectangular, you need to make a square out of it. Fold a piece of paper at the corner, matching two adjacent edges to form a triangle, then cut off the excess edge protruding from underneath it. As a result, you will get the required triangle.

   • The triangle will have one right angle (90 degrees) and two acute angles of 45 degrees.

2. Bring the triangle to one eye. Hold the sheet vertically so that the right angle (90º) is placed at the bottom and facing away from you. One of the short sides (leg) should be located horizontally (parallel to the ground), the second - vertically (from bottom to top). Position the triangle so that when you lift your eyes up, you can look along its long side.

   • Long side right triangle, along which your gaze is directed, is called the hypotenuse.

3. Move away from the tree until you see that its top coincides with the apex of the triangle (its upper acute corner). Close one eye while looking with the other along the long side of the triangle until the top of the tree appears above it. Make sure that your gaze, directed along the long side of the triangle, falls on the very top of the tree.

   Mark the appropriate spot on the ground and measure the distance from it to the base of the tree. This is what will happen almost full height of the tree. Your height should be added to the resulting value, since you looked at the tree not from the ground itself, but from the height of your eyes. Now you have found relatively exact height tree!

   • The principle on which this method is based is detailed below in the section “Using a clinometer or theodolite”. This method does not require any calculations, since it uses the simple fact that the tangent of an angle is 45º degrees (that's what sharp corners in our paper triangle) is equal to 1. Thus, we can write the following equality: (height of the tree) / (distance from the tree) = 1. Multiplying both sides of the equality by (distance from the tree), we get: height of the tree = distance from the tree.

Using a pencil (assistant required)

1. This method can be used as an alternative to the previous one (shadow comparison). Although the present method is less accurate, it can be used in cases where it is not possible to find the height of a tree by comparing the lengths of shadows, for example on a cloudy day. Plus, if you have a measuring tape, you can do without mathematical calculations. Otherwise, if you don't find a tape measure, some simple calculations will be required.

   Stand far enough away from the tree so that you can see the entire tree, from base to top, without tilting or raising your head. For greater measurement accuracy, your feet should be level with the base of the tree, neither higher nor lower than it. Stand so that nothing blocks or blocks the tree from you.

   Take a pencil in your hand and hold it out in front of you. Instead of a pencil, you can use another small straight object, such as a stick or ruler. Taking the pencil in your hand, straighten it so that the pencil is directly in front of you (between you and the tree).

   Close one eye and move the pencil until the tip aligns with the top of the tree. In this case, it is better to hold the pencil with the sharpened end up. It is necessary that the top edge of the pencil obscures the top of the tree from you, while you look at the tree “through” the pencil.

   Move your thumb along the pencil until the tip of your finger aligns with the base of the wood. Holding the pencil so that its top end is aligned with the top of the tree (see step 3), move thumb along the pencil to the place where you can see the base of the tree coming out of the ground (as before, while looking “through” the pencil at the tree with one eye). Now the pencil "covers" the full height of the tree, from its base to the top.

   Turn your hand so that the pencil is positioned horizontally (along the earth's surface). As you do this, keep your arm extended in front of you and make sure your thumb is still pointing toward the base of the tree.

   Ask your assistant to stand so that you can see him or her “on” the tip of the pencil. That is, your friend should stand in such a way that his feet “coincide” with the top of the pencil. In this case, the assistant should position himself at the same distance from you as the tree, no closer and no further. You and your assistant will be separated from each other by some distance (depending on the height of the tree), so you can communicate with him through gestures (using your second hand, which does not have a pencil), showing him where to move (further or closer, right or left ).

   If you have a tape measure with you, measure the distance between your assistant and the tree. Ask a friend to stay put, or mark the spot with a branch or rock. Then use a tape measure to measure the distance from this place to the base of the tree. This distance will be equal to the height of the tree.

   If you don't have a measuring tape handy, mark the height of your helper and the height of the tree on a pencil. Make a scratch or other mark on the pencil in the place where your thumb was located, thereby recording the height of the tree from your vantage point. Then, just as before with the tree, move the pencil so that it partially obscures your assistant, aligning the top of the pencil with the assistant's head, and the thumb resting on the pencil with his feet. Again, mark the position of your thumb on the pencil.

2. Calculate the height of the tree by finding a measuring tape. To do this, you will need to measure the distance between the tip of the pencil and the marks made on it, as well as the height of your assistant; This can be done at home without returning to the tree. Scale the lines on the pencil according to the height of your assistant. For example, if your friend's height mark is 5 centimeters (2 inches) from the tip of the pencil, and the tree height mark is 17.5 centimeters (7 inches) from the tip of the pencil, then the tree is 3.5 times taller than your friend. since 17.5 cm / 5 cm = 3.5 (7 inches / 2 inches = 3.5). Let's say your friend is 180 centimeters (6 feet) tall, then the height of the tree is 180 cm x 3.5 = 630 cm (6 x 3.5 = 21 feet).

   • Note: If you have a measuring tape with you when you are near a tree, there is no need to do any calculations. Read the above step “if you have a tape measure with you” carefully.

Using a clinometer or theodolite

1. This method allows you to obtain more accurate results. Although the above methods are quite reliable, with a little more advanced calculations and special tools you can get more accurate results. This is not as difficult as it seems at first glance: you only need a calculator with a function for calculating tangent, as well as a simple plastic protractor, a straw and a thread, with which you can make a clinometer yourself. A clinometer, or inclinometer, allows you to measure the inclination of objects, and in our case, the angle between you and the top of the tree. For this purpose, a more complex and precise instrument is used, called a theodolite, which includes a telescope or laser.

   • In the “Using a Sheet of Paper” method, a paper triangle serves as a clinometer. This method, in addition to greater accuracy, allows you to determine the height of a tree from any distance instead of approaching the tree or moving away from it, trying to align a sheet of paper with the tree.

2. Measure the distance to the observation point. Stand with your back to the tree and move away from it to a place that is level with its base, from where the top of the tree is clearly visible. At the same time, walk along a straight line, using a tape measure to measure the distance traveled from the tree. The distance from the tree can be arbitrary, but for this method It is best if it is 1-1.5 times the height of the tree.

   Now you know the height of the tree. Since the clinometer or theodolite was not located on the ground, but at the level of your eyes, to find the total height of the tree, you should add your height to the previously calculated value. To get more accurate results, you can measure the distance from your feet to your eyes and add it rather than full height from the feet to the top of the head.

   • If you are using a stationary theodolite, it is not your height that should be added, but the distance from the theodolite eyepiece to the ground.

• Many trees do not grow strictly vertically; their trunks are inclined. Using the elevation angle method, you can adapt it to sloping trees by measuring the distance between you and a point on the ground directly below the top of the tree (not between you and the base of the tree).
• You can improve the accuracy of the pencil method and elevation angle calculations by taking multiple measurements with different points around the tree.
• This could be a fun activity for students in grades 4 through 7.
• For more accurate calculations when using the shadow method, instead of a person’s height, you can take something whose length you know exactly (for example, a meter ruler or other straight long object).
• Be careful with units of measurement (multiply meters by meters or centimeters by centimeters).
• You can easily make a simple clinometer using a protractor. You will find instructions in this article.

Warnings

• The above methods do not work if the tree grows on a slope. In such cases, specialists use electronic theodolites, which are usually quite expensive.
• Although the elevation angle methods at correct use will give you results accurate to half a meter or a meter; they can easily be mistaken, especially if the tree is tilted or grows on a slope. If you need high precision, turn to the services of an aerial platform.

What does it mean to measure a physical quantity? What is a unit of physical quantity called? Here you will find answers to these very important questions.

1. Let's find out what is called a physical quantity

For a long time, people have used their characteristics to more accurately describe certain events, phenomena, properties of bodies and substances. For example, when comparing the bodies that surround us, we say that the book is smaller than bookshelf, and the horse is larger than the cat. This means that the volume of the horse is greater than the volume of the cat, and the volume of the book is less than the volume of the cabinet.

Volume is an example of a physical quantity that characterizes the general property of bodies to occupy one or another part of space (Fig. 1.15, a). In this case, the numerical value of the volume of each of the bodies is individual.

Rice. 1.15 To characterize the property of bodies to occupy one or another part of space, we use the physical quantity volume (o, b), to characterize movement - speed (b, c)

A general characteristic of many material objects or phenomena, which can acquire individual meaning for each of them, is called physical quantity.

Another example of a physical quantity is the familiar concept of “speed”. All moving bodies change their position in space over time, but the speed of this change is different for each body (Fig. 1.15, b, c). Thus, in one flight, an airplane manages to change its position in space by 250 m, a car by 25 m, a person by I m, and a turtle by only a few centimeters. That's why physicists say that speed is a physical quantity that characterizes the speed of movement.

It is not difficult to guess that volume and speed are not all the physical quantities that physics operates with. Mass, density, force, temperature, pressure, voltage, illumination - this is only a small part of the physical quantities that you will become familiar with while studying physics.

2. Find out what it means to measure a physical quantity

In order to quantitatively describe the properties of any material object or physical phenomenon, it is necessary to establish the value of the physical quantity that characterizes this object or phenomenon.

The value of physical quantities is obtained by measurements (Fig. 1.16-1.19) or calculations.

Rice. 1.16. “There are 5 minutes left before the train departs,” you measure the time with excitement.

Rice. 1.17 “I bought a kilogram of apples,” says mom about her mass measurements

Rice. 1.18. “Dress warmly, it’s cooler outside today,” your grandmother says after measuring the air temperature outside.

Rice. 1.19. “My blood pressure has risen again,” a woman complains after measuring her blood pressure.

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

Rice. 1.20 If a grandmother and grandson measure distance in steps, they will always get different results

Let's give an example from fiction: “After walking three hundred paces along the river bank, the small detachment entered the arches of a dense forest, along the winding paths of which they had to wander for ten days.” (J. Verne “The Fifteen-Year-Old Captain”)

Rice. 1.21.

The heroes of the novel by J. Verne measured the distance traveled, comparing it with the step, that is, the unit of measurement was the step. There were three hundred such steps. As a result of the measurement, a numerical value (three hundred) of a physical quantity (path) in selected units (steps) was obtained.

Obviously, the choice of such a unit does not allow comparing the measurement results obtained different people, since everyone’s step length is different (Fig. 1.20). Therefore, for the sake of convenience and accuracy, people long ago began to agree to measure the same physical quantity with the same units. Nowadays, in most countries of the world, the law adopted in 1960 is in force. International system units of measurement, which is called the “System International” (SI) (Fig. 1.21).

In this system, the unit of length is the meter (m), time - the second (s); Volume is measured in cubic meters (m3), and speed is measured in meters per second (m/s). You will learn about other SI units later.

3. Remember multiples and submultiples

From a mathematics course you know that to abbreviate the notation of large and small values different sizes use multiples and submultiples.

Multiples are units that are 10, 100, 1000 or more times larger than the base units. Sub-multiple units are units that are 10, 100, 1000 or more times smaller than the main ones.

Prefixes are used to write multiples and submultiples. For example, units of length that are multiples of one meter are a kilometer (1000 m), a decameter (10 m).

Units of length subordinate to one meter are decimeter (0.1 m), centimeter (0.01 m), micrometer (0.000001 m), and so on.

The table shows the most commonly used prefixes.

4. Getting to know the measuring instruments

Scientists measure physical quantities using measuring instruments. The simplest of them - a ruler, a tape measure - are used to measure the distance and linear dimensions of the body. You are also well aware of such measuring instruments as a watch - a device for measuring time, a protractor - a device for measuring angles on a plane, a thermometer - a device for measuring temperature, and some others (Fig. 1.22, p. 20). You still have to get acquainted with many measuring instruments.

Majority measuring instruments have a scale that allows for measurement. In addition to the scale, the device indicates the units in which the value measured by this device is expressed*.

On the scale you can set the two most important characteristics device: measurement limits and division value.

Measurement limits- this is the largest and smallest value physical quantities that can be measured by this device.

Nowadays, electronic measuring instruments are widely used, in which the value of the measured quantities is displayed on the screen in the form of numbers. Measurement limits and units are determined from the device passport or are set with a special switch on the device panel.

Rice. 1.22. Measuring instruments

Division price- this is the value of the smallest scale division of the measuring device.

For example, the upper measurement limit of a medical thermometer (Fig. 1.23) is 42 °C, the lower one is 34 °C, and the scale division of this thermometer is 0.1 °C.

We remind you: to determine the price of a scale division of any device, it is necessary to divide the difference of any two values ​​indicated on the scale by the number of divisions between them.

Rice. 1.23. Medical thermometer

• Let's sum it up

A general characteristic of material objects or phenomena, which can acquire individual meaning for each of them, is called a physical quantity.

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

As a result of measurements, we obtain the value of physical quantities.

When talking about the value of a physical quantity, you should indicate its numerical value and unit.

Measuring instruments are used to measure physical quantities.

To reduce the recording of numerical values ​​of large and small physical quantities, multiple and submultiple units are used. They are formed using prefixes.

• Security questions

1. Define a physical quantity. How do you understand it?
2. What does it mean to measure a physical quantity?

3. What is meant by the value of a physical quantity?

4. Name all the physical quantities mentioned in the excerpt from J. Verne’s novel given in the text of the paragraph. What is their numerical value? units of measurement?

5. What prefixes are used to form submultiple units? multiple units?

6. What characteristics of the device can be set using the scale?

7. What is the division price called?

• Exercises

1. Name the physical quantities known to you. Specify the units of these quantities. What instruments are used to measure them?

2. In Fig. Figure 1.22 shows some measuring instruments. Is it possible, using only a drawing, to determine the price of division of the scales of these instruments? Justify your answer.

3. Express the following physical quantities in meters: 145 mm; 1.5 km; 2 km 32 m.

4. Write down the following values ​​of physical quantities using multiples or submultiples: 0.0000075 m - diameter of red blood cells; 5,900,000,000,000 m - the radius of the orbit of the planet Pluto; 6,400,000 m is the radius of planet Earth.

5 Determine the measurement limits and the price of division of the scales of the instruments that you have at home.

6. Remember the definition of a physical quantity and prove that length is a physical quantity.

• Physics and technology in Ukraine
  

One of the outstanding physicists of our time - Lev Davidovich Landau (1908-1968) - demonstrated his abilities while still studying at high school. After graduating from university, he interned with one of the creators of quantum physics, Niels Bohr. Already at the age of 25, he headed the theoretical department of the Ukrainian Institute of Physics and Technology and the department of theoretical physics at Kharkov University. Like most outstanding theoretical physicists, Landau had an extraordinary breadth of scientific interests. Nuclear physics, plasma physics, the theory of superfluidity of liquid helium, the theory of superconductivity - Landau made significant contributions to all these areas of physics. For work in physics low temperatures he was awarded the Nobel Prize.

Physics. 7th grade: Textbook / F. Ya. Bozhinova, N. M. Kiryukhin, E. A. Kiryukhina. - X.: Publishing house "Ranok", 2007. - 192 p.: ill.

Lesson content lesson notes and supporting frame lesson presentation interactive technologies accelerator teaching methods Practice tests, testing online tasks and exercises homework workshops and trainings questions for class discussions Illustrations video and audio materials photographs, pictures, graphs, tables, diagrams, comics, parables, sayings, crosswords, anecdotes, jokes, quotes Add-ons abstracts cheat sheets tips for the curious articles (MAN) literature basic and additional dictionary of terms Improving textbooks and lessons correcting errors in the textbook, replacing outdated knowledge with new ones Only for teachers calendar plans training programs methodological recommendations

Vernier calipers are a very popular measuring tool. The design of the caliper is quite simple, so almost anyone can use it without much effort. preliminary preparation. It can be used to measure both external and internal dimensions. various parts, as well as the depth of the holes in them. Despite simple design, this instrument has different accuracy classes and can give readings with an accuracy of 0.1 to 0.01 mm. It received its name based on the main design detail. Thanks to its design, the caliper is rightfully considered one of the most versatile measuring instruments.

Using a caliper, you can measure both the external and internal dimensions of various parts, as well as the depth of the holes in them.

Fundamental design characteristics of a caliper

A vernier tool in principle, and a caliper in in this case, has as its main part a retractable rod with a measuring scale. This scale is divided into divisions of 1 mm, and its total length in the protozoa household model ShTs-1 ranges from 15 to 25 cm. There are also models of larger sizes, but they are used only on industrial enterprises and are much less common. It is this rod that determines the maximum value that this particular model of caliper can measure.

The ShTsTs digital caliper has a digital display mounted on a movable frame.

A special design feature of it is the presence of such a device as a vernier. This is an auxiliary scale that is movable relative to the main ruler. It helps to correctly determine the number of division shares on this ruler. The divisions on the vernier scale, also known as “vernier”, are a certain fraction smaller than the divisions of the main ruler. There can be 10 of them for a model with an accuracy of up to 0.1 mm, or 20 for models with an accuracy of up to 0.05 mm. The principle of operation of a vernier is based on the fact that it is much easier to determine by eye the coincidence of divisions than the relative location of one division between two others.

If it is necessary to measure external surfaces, such as the cross-section of a wire, large jaws are simply placed on both sides of the internal surfaces. The wire is clamped between them, and the zero division of the scale of the moving frame gives an indication on the main scale of the rod. Small jaws are shaped like scissor blades, which helps measure the diameter of a pipe or other hole on a scale without additional calculations. They have external working surfaces, having the profile of a sharpened blade, so they can measure such an indicator as the thread pitch.

Components and Applications

The tool consists of a fixed base and retractable fittings. They are made of tool steel. The caliper includes the following components:

1. The main rod on which all movable fittings are attached. The main scale is located on it.
2. A movable frame with a screw lock and pressed by an internal spring plate. There is a vernier scale on it. It can be applied directly to it, or it can be on a plate secured with screws. This allows you to adjust it relative to the scale on the bar.
3. Sponges for measuring external surfaces, or large sponges. One of them is mounted on a fixed rod, and the other on a movable frame. The ends have narrow surfaces, which gives additional features for measurement.
4. Measuring sponges internal surfaces, or small sponges. They are located according to the same principle opposite the previous ones along the central axis.
5. Ruler for measuring depths. Attached to a movable frame.

The ruler for measuring depth is mounted on a movable frame and moves along a groove made in the plane of the rod. It can also be used to measure internal grooves and shoulder distances. The rod is placed on its end perpendicular to the object being measured. The ruler extends until it rests on the bottom. To measure conical holes its end has a slight sharpening. After receiving the measurement result, it is recommended to fix the position of the instrument with a locking screw, and only then take readings.

Types of caliper designs and their markings

Along with the simplest mechanical model, the structure of which is discussed above, there are others. They can be divided into 4 main types, having 8 standard sizes. Their designs, as well as their purpose, have some differences. In addition to the double-sided caliper ShTs-1 discussed above, there is a one-sided version ShTsT-1. It has jaws on only one side and a ruler for measuring depths. Although it has a mechanical device, like ShTs-1, the material for its manufacture is hard, high-alloy steel. Such a tool helps to determine the external linear dimensions and depth of holes during abrasive action on the object being measured.

The instrument, called ShTs-2, is equipped with a double-sided design, but the jaws for measuring internal and external surfaces are combined, and have, respectively, flat surfaces on the inside and cylindrical surfaces on the outside. Opposite them are jaws of the same size for measuring external dimensions, which have sharpened edges. This allows you to not only measure, but also mark on the surface of the part being measured. In addition, this model has an auxiliary micrometer feed frame, which allows you to take readings with great accuracy.

The ShTs-3 caliper differs from the previous model only in its one-sided design. Its pair of jaws are designed to measure both internal and external dimensions. This model is designed to measure the largest sizes, so it is also quite large. And what larger sizes measuring device, the greater the resulting measurement error. Therefore, in addition to the designs described above, calipers are divided according to the indicators with which readings are taken.

According to this principle, they are divided into vernier ones, in which the readings are calculated independently based on the movement of the frame, into dial and digital ones. Dials marked ShTsK use the same mechanical principle. On the frame there is a digital scale connected to the rod by a gear transmission. Whole millimeters are read by the position of the edge of the frame, and their fractions are narrower by the dial. Such a caliper has a higher accuracy class than a vernier caliper and can be up to 0.01 mm. However, it is very vulnerable to mechanical damage and contamination of the rack from the parts being measured.

Turning production, installation of various pipeline systems, screw connections and other structures requiring increased precision.

At the same time, thanks to the design, almost everyone can use it. The ShTsTs digital caliper has a digital display mounted on a movable frame. A reading device is built into the frame, indicating the distance between the measuring jaws. There are buttons on the display that allow you to control them. The accuracy of such a device is 0.01 mm and allows you to measure the smallest parts, in particular, control threads. However, all the disadvantages electronic devices inherent in this instrument as well. Changes in rod parameters due to temperature changes immediately affect the display readings.

At the dawn of the development of knowledge about electricity, it was enough to operate with such concepts as voltage, conductor resistance, and current strength. Accordingly, voltmeters, ohmmeters, and ammeters were used to measure these quantities.

Modern electrical appliances are high-tech devices that incorporate many engineering solutions in their design, including various electronic modules. To debug or repair systems using these modules, it is necessary to measure many parameters related to the operation of the devices, for which a variety of instrumentation is used.

The simplest and most accessible device used for these purposes is a multimeter.

Purpose and types

The purpose of the device is guessed from the name. “Multi” is a prefix in compound words, meaning “many.” "Metreo" is translated from Greek language how to "measure". It turns out that a multimeter is a device that can measure many different parameters. Of course, almost all measured parameters are related to electricity in one way or another.

It is impossible to measure, for example, a person’s blood pressure or air humidity with a multimeter, but using some models, you can measure the temperature of an object, liquid or gas.

By design, the following types of multimeters are distinguished:

1. analog;
2. digital.

Analog ones, which previously appeared in use, are noticeably inferior to digital ones in the accuracy of measurements and the number of measured parameters. They require additional setup and preparation before taking the actual measurement.

The design of devices may contain elements whose operation is based on the use of the phenomenon of magnetism.

The accuracy of analog devices is highly dependent on the presence of magnetic fields in the measurement area, humidity and temperature environment. The readings on such devices are read from a scale that is multifunctional.

Digital multimeters are much easier to use than analog ones, they have a wider range of functions and measurement limits, but they are also more expensive. The readings are displayed as digital information on a liquid crystal display. Very often the display is backlit for ease of use of the multimeter in low light conditions.

Application

There are times when a person, being a professional in some field not related to electricity, has absolutely no idea why a multimeter is needed. This is possible because until recently, literally a couple of decades ago, these devices were produced only in analog versions and were quite expensive.

They were used mainly by professional electricians, they were cumbersome, and sometimes required the use of an additional power source.

Recently, multimeters have been made compact, inexpensive, and have become much easier to use. Any zealous owner now has at least the simplest model from a large family of these devices.

After all, if the cause of a malfunction of any household appliance is established, then eliminating it may be within the power of an ordinary person who does not have the professional knowledge and skills of an electrician. Moreover, often, having such a useful measuring device at hand, its owner does not always use all the functions of the multimeter.

The multimeter is used when repairing electrical appliances, debugging circuits, and electronic devices. In daily life, it can be used in electrical repair household appliances, electrical parts of cars, motorcycles, troubleshooting electrical networks, wiring, repairing radio equipment. The scope of application is very wide.

What parameters does it measure?

How is the same device used in seemingly different situations?

It's very simple. IN electrical devices There are necessarily many elements - electric motors, radio components, switches, inductors, microcircuits, relays and other components. Their operation is necessarily associated with the presence of electricity, which is characterized by such parameters as voltage and current.

All types of multimeters can be used when measuring AC and DC voltage, the resistance of a conductor or section of a circuit, and the current strength in a section of a circuit with the load turned on.

A digital multimeter also provides the ability to measure the capacitance of capacitors.

Using a multimeter, you can check the health of diodes and transistors. Many models can measure frequency. Some types of multimeters have temperature sensors.

When servicing household appliances, the use of a multimeter is usually based on the need to check whether there is current or not. That is, the supply cables and cords are checked for breaks, as well as connectors electrical circuits for contact. In this case, the multimeter is used as an ohmmeter.

Checking transformers and electric motors

Sometimes it becomes necessary to check the input and output voltage on power supply transformers. To measure these parameters, you must use the device as a voltmeter, making the appropriate settings.

Many household machines contain electric motors, and if the motor does not turn on, you have to check the presence of supply voltage at the terminals.

If no faults are found in the supply circuit, it is necessary to check the serviceability of the rotor and stator of the motor. To do this, you can check the integrity of the winding wires and the presence of an interturn short circuit.

The multimeter is used both as a voltmeter and an ohmmeter.

Checking relays and electronic circuits

Sometimes you have to check automation elements - relays and electronic units. The relay is checked, as a rule, for the value of the opening current, for which a corresponding load is connected to the circuit, and a multimeter operating in ammeter mode is connected in series with it.

In control units, the voltage on the corresponding contacts or the resistance between certain pairs of contacts is checked in accordance with their functional purpose.

The performance of individual elements is checked using a multimeter electrical diagrams, for example, semiconductor devices (transistors, thyristors), capacitors.

To do this, the parts are desoldered from the boards and inserted into special connectors on the device body. Such functions are usually available in digital multimeters.

Application in motorcycle and automotive equipment

When servicing automobiles and motorcycles (motorcycles also include various garden machines with engines internal combustion And boat motors and other similar equipment) using a multimeter, you can check the serviceability of generators, starters, and batteries.

In all these cases, a multimeter is used to obtain voltage and current data. Measurements can be carried out in various modes operation of the units being tested.

In internal combustion engines, the ignition system is checked. To do this, candles can be rung and the resistance of the insulators is checked. Ignition coils are tested.

If any systems fail, the wiring in the vehicles is checked for breaks or short circuit, drive motors.

Using a multimeter, you can determine, for example, whether the spiral in an incandescent lamp is intact without removing the lamp from the headlight unit. To do this, just disconnect the headlight power connector and you can measure the lamp resistance, and then the supply voltage.

As a result, it can be determined whether the lamp really needs to be changed or whether it is necessary to look for an open circuit. In the latest car models, this is very important, since to replace a lamp sometimes you have to disassemble almost the entire front trim.

Checking the electrical wiring

When installing new or repairing old wiring, there is always a need to test the cables, as well as check the functionality of electrical installation products and circuit breakers. All these operations can also be successfully carried out using a multimeter.

Correct use of a multimeter, this universal measuring instrument with many functions and capabilities, helps to significantly improve the operating conditions of equipment.

A multimeter helps to timely identify the need for its repair, while increasing maximum term operation. This ultimately allows owners to avoid extra costs for repairs and renovations.

During production construction work or minor repairs often require measuring tools. Usually they are rulers or tape measures. But when measuring pipe diameter or hole depth, these tools are not suitable. For such purposes, more precise measuring instruments are used - calipers.

This device is universal. It can be used to measure the external and internal dimensions of parts. Calipers have gained wide popularity in everyday life, as they have a simple design and are easy to use. Using such a device, you can quickly and easily take measurements with high accuracy.

Vernier caliper device

1 — Sponges for internal measurements
2 — Sponges for external measurements
3 - Clamping screw
4 - Movable frame
5 - Vernier
6 - Rod
7 — Bar scale
8 - Depth gauge

All instruments similar to calipers have a measuring rod, which is how the device got its name. There is a main scale on the rod, which is necessary when measuring first.

A movable frame with a printed scale can move along the bar. The scale on the rod is called a vernier, which has more precise markings in fractions of divisions. This provides increased measurement accuracy. The degree of accuracy of a caliper, depending on the design, can reach hundredths of a millimeter.

Calipers have two types of jaws:

• To measure internal dimensions.
• For measuring external dimensions.

There is also another measuring element of the device, which is called a depth gauge. It can be used to measure hole depth and other dimensions.

Digital calipers are designed in a similar way. However, instead of a vernier, a digital scale is used, which increases the ease of use and measurement accuracy of the device.

1 - Clamping screw
2 - Battery
3 - Roller length change
4 - Reset
5 - On/Off
6 - Switch mm/inches

Like all measuring instruments, digital instruments are equipped with a scale with a division value of 0.01 mm. The permissible error is considered to be a deviation of the measurement result down or up by 10%. In industry, all measuring instruments are subject to metrological control every six months.

The retail chain sells calipers packaged in a case. When purchasing a tool, it is recommended to inspect the measuring jaws. They should be smooth, and there should be no gap when they are compressed.

The vernier scale should be in the zero position when the jaws are closed. The lines marking the scale divisions along the vernier must be clearly marked. The kit of the device must include a passport with a mark on the accuracy verification performed.

Types and features

Main types of calipers:

There are several subtypes of different calipers depending on the size, design features and operating principle.

ШЦ-I

This is the simplest and most popular model of the device, which is widely used in industrial production. It is called "Columbian" after the name of the manufacturer's company, which produced the instrument in wartime(Columbus).

The device can measure internal and external dimensions and depth. The measurement interval is from 0 to 150 mm. The measurement accuracy reaches 0.02 mm.

SCC-I

This digital measuring tool model has a similar design to the classic caliper. Measurement interval 0-150 mm. One of its advantages can be called more high accuracy when measuring due to the presence of a digital indicator.

The convenience of using such a digital device is that the indicator can be reset to zero at any measurement point. You can also easily switch from metric to inch with just one button.

When purchasing a digital model, you need to pay attention to the presence of zero readings when the jaws are closed, and also when the locking screw is tightened, the numbers on the display should not jump.

ShTsK-I

In this design of the caliper there is a rotary indicator with a round scale, the division value of which is 0.02 mm. These calipers are convenient to use for frequent measurements in production. The indicator arrow is clearly visible for quick control of the result; it does not have jumps, unlike digital models. This device is especially convenient to use in the technical control department for measurements of similar standard sizes.

ШЦ-II

Such rulers are used for measuring internal and external dimensions, as well as for marking parts before processing. Therefore, their jaws have attachments made of hard alloy to protect them from rapid wear. The measurement interval of the ShTs-II series of devices is in the range of 0-250 mm and the measurement accuracy is 0.02 mm.

ШЦ-IIIand SCC-III

Large parts are most often measured with this model of instrument, since its measurement accuracy is higher than other models and is 0.02 mm for mechanical instruments, and 0.01 mm for digital instruments.

The largest dimension to measure is 500mm. The jaws in such models are directed downwards and can have a length of up to 300 mm. This makes it possible to measure parts over a wide range.

Special purpose calipers

Let us briefly consider several specialized models of calipers designed for special types works Such devices appear quite rarely in the retail chain.

• SHCT– used for measuring pipes, it is called a pipe caliper.
• SHTSTSV— for measuring internal dimensions, has a digital display.
• SHTSCN– similar to the previous device, used to measure external dimensions.
• SHCCU— universal digital meter, the kit includes a set of attachments for hard-to-reach measurements: center-to-center distances, pipe walls, external and internal dimensions, etc.
• SHCD– a device for measuring the thickness of brake discs and parts with various protrusions.
• SHTSCP— Vernier calipers are used to measure the tread depth of car tires.
• SHTSTM– calipers designed specifically for measuring center-to-center distances.

Rules for using calipers

• Check the tool. To do this, bring the caliper jaws together and check the accuracy of their closure for the presence of clearance between them.
• Take the tool in right hand, and the measured part in the left hand.
• To measure external size parts, it is necessary to separate the lower jaws of the tool and place the part being tested between them. You should be careful when doing this, as the edges of the jaws are sharp and you can get injured if you handle the tool carelessly.
• Squeeze the jaws of the caliper until they come into contact with the part. If the material used to make the part has a soft structure, then strong compression of the jaws will lead to inaccurate measurements. Therefore, the jaws must be squeezed carefully, only until they come into contact with the surface of the part. To move the caliper frame, use your thumb.
• Check the position of the jaws relative to the part. They must be at an equal distance from the edges of the part; tool distortions are not allowed.
• Secure the screw intended for clamping the movable frame. This allows you to maintain the position of the frame for accurate measurement results. It is advisable to tighten the screw with your thumb and index finger, while at the same time holding the instrument in one position with the same hand so as not to move it to ensure measurement accuracy.
• Put the part aside, and take the fixed caliper without the part to take the measurement results.
• The instrument reading stage is very important, since inaccuracy in measurement can lead to serious consequences in production.

Place the caliper directly in front of your eyes.

1 — Bar scale
2 - 21 divisions
3 — Vernier scale

— The figure shows the measurement procedure. On the left are jaws for external measurements with the part being measured, and on the right are scales: vernier and main. Their divisions will determine the measurement result.
- First you need to count the number of whole millimeters. To do this, you need to find the division on the rod scale that is closest to the vernier zero. This division is indicated by the first upper red arrow. In our case, this value is 13 mm. This value must be remembered or written down.
— Next you need to calculate fractions of a millimeter. To do this, you need to find a division on the vernier scale that coincides with the division on the rod scale. This division in the figure is shown by the second red arrow.
- Next, you need to determine the division number in order, for our case it turns out to be 21.
— Then you need to multiply this number by the value of the vernier scale division. In our example, the division value is 0.01 mm.
- Now it is necessary to calculate the exact value of the measurement determined by the caliper. To do this, you need to add the whole number with fractions of a millimeter. The result is 13.21 mm.

• When finished using the tool, clean it, loosen the screw, close the jaws and put it in the case. If the instrument will be stored for a long time, it is recommended to treat it with an anti-corrosion solution.

If you have a dial or digital caliper, the measurement process becomes much easier, since nothing needs to be calculated, the finished result will be visible on the display or dial.