Classification of measuring instruments. Control and measuring instrument. Construction measuring tool

Test instruments and measurement technology

The simplest measuring instruments include a scale ruler, calipers, and bore gauge.

The scale ruler is intended for measuring flat surfaces, as well as for determining dimensions measured with a bore gauge or calipers. Scale rulers are manufactured in different lengths from 100 to 1000 mm. The scale division value is 0.5 or 1 mm; to facilitate counting, every 5 and 10 mm are marked with elongated strokes. The zero division of most rulers is applied at the left end. When measuring, the ruler is applied to the part being measured so that the zero line exactly coincides with the beginning of the line being measured. In Fig. Figure 13 shows how to measure using a scale bar.

Rice. 13. Techniques for measuring with a scale ruler

Calipers are used to measure the external dimensions of parts. The value measured by the calipers is then determined by placing the calipers on the scale ruler. Calipers, like the simplest bore gauge, are rarely used.

A bore gauge is used to measure the internal dimensions of parts. The measured value is also determined using a scale bar.

Vernier calipers belong to multidimensional sliding measuring instruments (Fig. 14, a). It is intended for measuring external and internal dimensions and markings.

Rice. 14. Vernier calipers (a), examples of measuring the size and reading measurements with an accuracy of 0.1 mm (b, c, d)

A caliper consists of a rod with jaws rigidly attached to it, a frame with jaws moving along the rod, a device for micrometric feed, consisting of a slider, a locking screw, a nut and a screw.

The frame is moved as follows. The engine 6 is secured with a locking screw, and the frame locking screw is released. After this, by rotating the nut, the screw and the frame associated with it are slowly moved. The caliper has a vernier.

Calipers are produced with a measurement accuracy of 0.1; 0.05 and 0.02 mm. The last two have a micrometric feed, allowing you to install the caliper with high precision. The leftmost strokes of the vernier and the rod are called zero and when the jaws are closed they coincide. To determine the size to be measured, with the jaws of the caliper apart, count the whole number of millimeters that the left zero vernier stroke has passed along the rod, and then find the vernier stroke that exactly coincides with any division of the rod scale. The ordinal number of this division determines the fractions of a millimeter that should be added to the whole number of millimeters. When measuring internal dimensions, the thickness of the jaws indicated on them should be added to the reading made on the main scale and vernier. Examples of readings are shown in Fig. 14, b, c, d.

A depth gauge (Fig. 15, a) is used to measure the depth of holes, grooves on shafts, etc. Measurement with a depth gauge is carried out in the same way as with a caliper.

A vernier gauge (Fig. 15, b) is used to measure the thickness of wheel teeth. A vernier gauge is a combined measuring instrument consisting of two fixed rods that form a single unit and two movable verniers. The vertical vernier is designed to set the height at which the tooth thickness should be measured, and the horizontal vernier is designed to measure the tooth thickness at a given height. The measurement accuracy of the caliper is 0.02 mm.

The micrometer is used to measure the external dimensions of parts with an accuracy of 0.01 mm. The most common are micrometers with the following measurement limits: from 0 to 25 mm, from 25 to 50 mm, from 50 to 75 mm and from 75 to 100 mm.

The micrometer (Fig. 16) has a bracket into which a hardened and ground heel is pressed, a micrometer screw, a stopper, a stem, a drum and a ratchet.

Rice. 15. Vernier depth gauge (a), caliper gauge (b):
1 - locking screw, 2 - slider, 3 - micrometer screw, 4 - nut

Rice. 16. Micrometer

The ratchet is connected to the drum by a ratchet, pressed by a spring, and 50 divisions are marked on the left end of the drum, which is beveled along the circumference. The micrometer screw has a thread with a pitch of 0.5 mm, therefore, for one revolution of the screw, its end moves by 0.5 mm, and when the drum is turned by one division, the screw moves by 0.01 mm. On the surface of the stem there are divisions with an axial stroke.

Rice. 17. Micrometric bore gauge (a), extension to it (b)

To measure a part, it is placed between the micrometer screw and the heel, after which the drum is turned using a ratchet and the screw is pulled out until it comes into contact with the part. When the screw rests on the part being measured, the ratchet will turn freely, and the screw and drum will stop. To determine the measured size, you need to count the number of millimeters on the stem scale, including the half-millimeter division passed by the reference stroke (0.5), and then look at what number on the beveled part of the drum coincides with the axial stroke of the stem. This number will correspond to hundredths of a millimeter, which must be added to the previous data.

Rice. 18. Micrometric depth gauge

Rice. 19. Squares

A micrometric bore gauge (Fig. 17) is used to determine the internal dimensions of parts with an accuracy of 0.01 mm. A micrometric bore gauge consists of a micrometric screw (Fig. 17, a), a drum, a sleeve with a locking screw, and a tip with a spherical measuring surface. There is also a spherical measuring surface on the right side of the micrometer screw. Dimensions are measured in the same way as when measuring with a micrometer.

The micrometer bore gauge has a set of extensions that extend the measurement range. At one end of the extension there is an internal thread (Fig. 17, b), and at the other end there is an external thread. The end of the extension with internal threads is screwed onto the bore gauge stem, and the end of the extension with external threads is used to screw an additional extension onto it in order to increase the measurement limits.

Rice. 20. Universal protractor of the Semenov system

Rice. 21. Goniometer UG-2

The micrometric depth gauge (Fig. 18) is used to measure blind holes and recesses with an accuracy of 0.01 mm. It consists of a base, a drum, a ratchet, a vernier, a stopper, and a measuring rod. The principle of measuring with a depth gauge and a micrometer is the same.

To measure angles, as well as determine the accuracy of filing planes along the “clearance”, squares and universal protractors are used. Squares (Fig. 19) are usually made of steel.

The UG-1 goniometer (Fig. 20) of the Semenov system is universal, designed for measuring external angles. It consists of a base on which there is a scale from 0 to 120°, rigidly connected to a ruler, a movable ruler, a clamp, a removable square, a vernier and a micrometric feed device.

The UG-2 protractor (Fig. 21) consists of a base, a base ruler, a sector, a square, a removable ruler, clamps and a vernier. This protractor can measure external and internal angles.

On the main scale of protractors, degrees are counted, and on the vernier scale, minutes.

Limit gauges for measuring holes are made in the form of double-sided cylinders (Fig. 22) and are called plug gauges, and for measuring shafts - in the form of one-sided and double-sided staples, called gauge gauges (Fig. 23, a, b). Limit gauges can determine the largest and smallest permissible dimensions of parts.

In extreme gauges, one side is called passable and the other is called nonpassable. The go-through side of the plug gauge is used to measure the smallest hole, and the no-go side is used to measure the largest. With a clamp gauge, on the contrary, the largest shaft size is determined by the go-through side, and the smallest by the non-go-through side. When measuring, the pass side of the gauge must pass freely into the hole or along the shaft under the influence of the weight of the gauge. The non-go side of the gauge should not go into the hole or along the shaft at all. If the non-passing side of the gauge passes, the part is rejected.

Radius templates are used to measure the radii of curvatures of products.

Such templates are made in the form of thin steel plates with convex or concave curves. The templates are stamped with numbers showing the size of the radius of curvature in millimeters.

Probes. To measure the size of the gaps between parts, feelers are used (Fig. 24), which are steel plates of various thicknesses. Each plate indicates its thickness in millimeters.

Thread control is carried out using thread plug gauges, threaded rings and templates.

Thread plug gauges (Fig. 25, a) are used to check the threads of nuts. They are made from tool steel and look like a bolt with a precise thread profile. The nut thread is checked by screwing it onto the go or non-go side of the plug gauge.

Threaded rings (Fig. 25, b) are used to check the threads of bolts and represent a nut with an exact thread profile. The bolt thread is checked by screwing it into the threaded ring. One ring is a pass-through gauge and the other is a non-go-through gauge.

The thread gauge (Fig. 26) is designed to check and determine the thread pitch on bolts, nuts and other parts. It is a set of steel plates - threaded templates with tooth profiles corresponding to the profiles of standard metric or inch threads. Thread gauges usually have a set of templates with metric threads on one end and inch threads on the other. Each template is marked with thread dimensions.

Rice. 22. Size control with a double-sided plug gauge

Rice. 23. Double-sided (a) and single-sided (b) staple gauges

Rice. 25. Threaded plugs (a) threaded ring (b)

To check the threads on a bolt or nut, you need to apply the thread gauge templates successively until you find a template whose teeth exactly match the threads of the part without clearance. The measured thread will correspond to the size of this template.

The indicator is designed to measure deviations of dimensions from the specified ones, as well as to detect the ovality and taper of shafts and holes. In the repair business, the dial indicator is most widely used, the structure of which is shown in Fig. 27.

The indicator body contains a mechanism consisting of gears, a rack, a spiral spring, a sleeve, a measuring rod with a tip, a speed indicator, and a scale with an arrow. The large scale of the indicator has 100 divisions, each of which corresponds to 0.01 mm. When the measuring rod moves by 0.01 mm, the arrow will move around the circle by one division of the large scale, and when the rod moves by 1 mm, the arrow will make one revolution. The indicator scale is set to the zero position by rotating it by the rim.

Before measuring the product, the indicator is fixed in the bracket of the universal stand (Fig. 28) so that the tip of the measuring rod touches the surface of the product being measured. Next, behind the rim 5, set the zero division of the scale against the arrow (Fig. 27). After this, the product or indicator is slowly moved. The amount of deviation is determined by the arrow readings on the indicator scale.

Rice. 24. Probes

Rice. 26. Thread gauge

Rice. 27. Dial indicator:
1 - measuring rod, 2 - sleeve, 3, 10, 11, 13 - gears, 4 - scale, 5 - rim, 6 - body, 7 - arrow, 8 - speed indicator, 9 - spiral spring, 12 - spring, 14 - measuring tip

Rice. 28. Indicator with universal stand:
1 - the indicator itself, 2 - articulated lever, 3 - stand, 4 - base

Rice. 29 Indicator bore gauge

An indicator bore gauge (Fig. 29) is used to measure the diameters of engine cylinders. A full turn of the indicator needle corresponds to a change in dimension A by 1 mm. Since the scale has 100 divisions, the scale division value is 0.01 mm. The indicator arrow is set to zero by turning the rim. The indicator comes with a set of interchangeable tips that allow you to measure cylinders of various diameters.

Optical measuring instruments. Measuring instruments based on optical measurement principles include optimeters, instrumental microscopes, and various measuring machines.

Pneumatic instruments are used to measure the external and internal surfaces of precision parts, as well as to determine the cleanliness of surface treatment. Pneumatic devices operate on compressed air, which is supplied by a compressor. The advantage of such devices is the simplicity of their design and maintenance.

Electrical measuring instruments make it possible to make measurements with high accuracy. Such devices are based on electrical contact, capacitive and inductive measurement methods.

Measurement errors and their causes. When measuring parts, there is always some difference between the actual size of the part and the size obtained as a result of measurement. The difference between the measured value and the actual value is called error or measurement error.

The main causes of measurement errors are the following:
– inaccurate installation of the measured part or measuring tool;
– errors when taking instrument readings, which arise in cases where observation when taking readings is carried out from the wrong angle of view. It is always necessary to observe in a direction perpendicular to the plane of the scale;
– violation of the temperature conditions under which measurements must be made. The state standard for measurement provides a normal temperature of 20 °C. In practice, the part being measured often has a lower temperature than the temperature of the measuring instrument; this also leads to errors, since it is known that metals change their dimensions when the temperature changes. When cooled they contract and when heated they expand. When heated by 1 °C over a length of 1 m, metals elongate by the following values ​​(mm): steel - 0.012, cast iron - 0.010, bronze - 0.018, brass - 0.019, aluminum - 0.024;
– the surface of the part being measured is dirty or dirty;
– measuring instrument;
– errors of the measuring instrument;
violation of the constancy of the measuring force for which the measuring instrument is designed.

Storage and care of measuring instruments. Measuring instruments are stored in dry, warm rooms. Do not store instruments in damp areas or in areas with sudden temperature fluctuations, as this will lead to corrosion of the instruments. Each tool should have its place.

The simplest tools are stored in cabinets, on racks or hung on the walls. Complex instruments, such as micrometers, calipers, gauges, etc., are stored in special cases.

To protect against corrosion, measuring instruments are lubricated with acid-free petroleum jelly or bone oil. For long-term storage, the instrument is wrapped in oiled paper to protect it from contamination and exposure to humid air. Before work, the measuring surfaces of the instrument are washed with gasoline and wiped with a clean cloth, and after finishing work they are wiped again, then lubricated and put in their place.

Measuring instruments must be checked regularly using precision test instruments.

TO Category: - Car maintenance

Modern production is unthinkable without measuring instruments; various types of them are used everywhere. With the help of monitoring the quality of products and various technological production processes. The measuring instrument is used in mechanical engineering, scientific laboratories, construction and in everyday life.

Measuring instruments are measuring instruments for providing results of measured physical quantities within a strict range. If a tool, in addition to physical parameters, allows you to determine whether the dimensions of an object are within acceptable values, then it is a control and measuring tool.

Measuring tools allow you to determine the geometric shape and size of an object, its density and elasticity, straightness and flatness.

Every measuring instrument has an error, because it is almost impossible to make an absolutely accurate measurement. The price of the instrument often depends on the value of this error. The smaller the error, the higher the cost of the product. But when using any tool, measurement error is possible. This occurs due to improper use of the tool, its malfunction or contamination. Errors also occur when the measured object is contaminated or when the temperature regime is not observed. To reduce the likelihood of error and reduce the error, you must follow the operating rules of the measuring instrument.

According to GOST, measuring instruments are divided into 8 groups:

• Smooth calibers
• Threaded gauges
• Complex and profile gauges
• Measures and calibration tools
• Vernier devices, tools and accessories
• Mechanical devices, tools and accessories
• Optomechanical and electromechanical devices, tools and accessories
• Pneumatic instruments and accessories

The first 3 groups refer to special types of measuring instruments, the next 5 to the universal type. Universal instruments are used to measure various linear parameters of a product, regardless of its configuration.

They include the following widely used types of measuring instruments:

1. Vernier tools, the operation of which is based on the use of a vernier, which allows you to count fractional divisions (vernier calipers - used for high-precision measurements of external and internal measurements, as well as the depth of holes, vernier depth gauge - needed to measure the depth of holes with high accuracy, caliper gage - used for marking parts, depth of grooves and recesses).
2. A level that allows you to measure the deviation of structural parts horizontally and vertically.
3. , which allows you to measure small sizes with high accuracy.
4. A bore gauge measures the size of holes, grooves and other internal surfaces.
5. Squares and protractors that allow you to visualize and measure angles.
6. Feeler gauges designed to control gaps between surfaces.
7. Templates, depending on the type, used to measure the radius of a surface or the pitch of a thread profile.

You can also add the usual rulers and tape measures to the universal measuring tools.
Specialized measuring tools include various gauges that are designed to check the correct size and shape of products and help determine that the products will fit together and the assembly will be correct. Calibers allow you to measure one specific size of a product. They do not measure the actual size, but allow you to check that the product has not gone beyond the boundaries indicated in the drawing.

Trading house "Kvalitet" will provide you with a wide range of all types of measuring equipment.

The correctness of the required dimensions and shape of parts during their manufacture is checked using a line (scale) measuring instrument, as well as straight edges, plates, etc.

Therefore, in addition to a standard set of working tools, a mechanic must have control and measuring tools. These include: scale ruler, tape measure, calipers and bore gauge, vernier calipers, square, measuring rod, protractor, protractor, straight edge, etc.

The scale bar has division lines located from each other at a distance of 1 mm, 0.5 mm and sometimes 0.25 mm. These divisions make up the measuring scale of the ruler. For the convenience of measuring dimensions, each half-centimeter scale division is marked with an elongated stroke, and each centimeter division with an even more elongated stroke, above which a number is placed indicating the number of centimeters from the beginning of the scale. A scale ruler is used to measure external and internal dimensions and distances with an accuracy of up to 0.5 mm, and with experience, up to 0.25 mm. Scale bars are made rigid or elastic with a scale length of 100, 150, 200, 300, 500, 750 and 1000 mm, a width of 10–25 mm and a thickness of 0.3–1.5 mm from carbon tool steel grades U7 or U8.

Measurement techniques using a scale bar are shown in Fig. 9.

Rice. 9. Scale metal rulers and methods of measuring them

The tape measure is a steel tape, on the surface of which there is a scale with a division value of 1 mm (Fig. 10). The tape is enclosed in a case and is pulled into it either by a spring (self-rolling tapes), or by rotating a handle (simple tapes), or pushed in manually (grooved tapes). Self-rolling and grooved tape measures are manufactured with scale lengths of 1 and 2 m, and simple ones with scale lengths of 2, 5, 10, 20, 30 and 50 m. Tapes are used to measure linear dimensions: length, width, height of parts and distances between their individual parts parts, as well as the lengths of arcs, circles and curves. When measuring the circumference of the cylinder, a steel tape measure is wrapped tightly around it. In this case, the scale division coinciding with the zero division indicates to us the length of the measured circumference. Such techniques are usually used when it is necessary to determine the length of the sweep or the diameter of a large cylinder, if direct measurement of it is difficult.

Rice. 10. Roulettes:

a – push-button self-collapsing, b – simple, c – grooved, manually pushed in

To transfer dimensions to a scale bar and control the dimensions of parts during their manufacture, calipers and bore gauges are used.

Calipers are used to measure the external dimensions of parts: diameters, lengths, thicknesses of shoulders, walls, etc. It consists of two legs 150–200 mm long, curved along a large radius, connected by a hinge (Fig. 11, A). When measuring, take the caliper by the hinge with your right hand and spread its legs so that their ends touch the part being tested and move along it with little effort. The size of the part is determined by placing the legs of the calipers on the scale ruler.

A spring caliper (Fig. 11, b) is more convenient; the legs of such a caliper tend to move apart under the pressure of the ring spring, but nut 2, screwed onto a clamping screw 3, mounted on one leg and freely passing through the other, prevents this. By rotating the nut 2 by screw 3 with fine threads, the legs are set to a size that cannot be changed arbitrarily. The measurement accuracy with calipers is 0.25 – 0.5 mm.

Rice. 11. Calipers and bore gauge. Measurement methods

It is made from carbon tool steel U7 or U8, and the measuring ends at a length of 15–20 mm are hardened.

The bore gauge is used to measure internal dimensions: diameter of holes, sizes of grooves, recesses, etc. In Fig. 11, a, b ordinary and spring bore gauges are shown. Unlike calipers, it has straight legs with bent jaws. The device of the bore gauge is similar to that of a caliper.

When measuring the diameter of a hole, the legs of the bore gauge are spread until they lightly touch the walls of the part and then inserted vertically into the hole. The measured size of the hole will correspond to the actual size only if the bore gauge is not skewed, that is, the line passing through the ends of the legs will be perpendicular to the axis of the hole. The size is measured using a measuring ruler; in this case, one leg of the inside gauge is supported by the plane to which the end face of the measuring ruler is pressed at a right angle, and the size is measured along it (Fig. 11, V). In Fig. 11, d shows the measurement of the spread of the legs of the caliper using a caliper. This ensures greater accuracy (up to ±0.1 mm) than when reading using a ruler.

Bore gauges are made from carbon tool steel U7 or U8 with hardening of the measuring ends at a length of 15–20 mm.

The measurement accuracy that can be obtained using a scale ruler, folding meter or tape measure does not always satisfy the requirements of modern mechanical engineering. Therefore, in the manufacture of critical machine parts, more advanced scale tools are used, which make it possible to determine dimensions with increased accuracy. These tools primarily include calipers.

Vernier calipers are used to measure both external and internal dimensions of parts (Fig. 12, a). It consists of a rod 8 and two pairs of jaws: lower 1 And 2 and upper 3 and 4. Sponges 1 And 4 made integral with frame 6 sliding along the rod. Using screw 5, the frame can be fixed in the required position on the rod. The lower jaws are used for measuring external dimensions, and the upper jaws are for internal measurements. Depth gauge 7 connected to the movable frame 6, moves along the groove of the rod 8 and is used to measure the depth of holes, grooves, recesses, etc. Whole millimeters are counted on the rod scale, and fractions of a millimeter are counted on the vernier scale 9, placed in the cutout of the frame 6 caliper.

The vernier scale has ten equal divisions over a length of 9 mm; thus, each division of the vernier scale is less than a division of the scale (ruler) by 0.1 mm. When measuring a part with a caliper, first count a whole number of millimeters on the rod on a scale, looking for it under the first stroke of the vernier, and then use the vernier to determine tenths of a millimeter. In this case, mark the division of the vernier, coinciding with the division on the rod. The ordinal number of this division shows tenths of a millimeter, which are added to the whole number of millimeters. In Fig. 12, b three positions of the vernier relative to the rod scale are shown, corresponding to the dimensions: 0.1; 0.5 and 25.6 mm.

Rice. 12. Vernier caliper with measurement accuracy of 0.1 mm

It is often necessary to manufacture parts whose surfaces meet at different angles. To measure these angles, squares, angle gauges, protractors, etc. are used. Squares and angle gauges are the most common tools for checking right angles. 90° steel squares come in a variety of sizes, solid or multi-piece (Figure 13).

Squares are manufactured in four accuracy classes: 0, 1, 2 and 3. The most accurate squares are class 0. Accurate squares with chamfers are called patterned (Fig. 13, A, b). To check right angles, a square is placed on the part being tested and the correct processing of the angle being checked is determined in the light. When checking the outer corner, the square is placed on the part with its inner part (Fig. 13, V), and when checking the inner corner - with the outer part. Having placed one side of the square on the machined side of the part, pressing it lightly, combine the other side of the square with the machined side of the part and judge by the resulting gap the accuracy of the right angle (Fig. 13, d). Sometimes the size of the lumen is determined using probes. It is necessary to ensure that the square is installed in a plane perpendicular to the line of intersection of the planes forming a right angle (Fig. 13, d). In inclined positions of the square (Fig. 13, e, g) Measurement errors are possible.

Rice. 13. Squares with an angle of 90° and methods of their use

Simple fry (Fig. 14, A) consists of a clip 1 and rulers 2 , hingedly fixed between two strips of the cage. The hinged fastening of the holder allows the ruler to occupy a position in relation to the holder at any angle. The mold is installed at the required angle according to the sample of the part or along the corner tiles. The required angle is fixed with a screw 3 with wing nut.

A simple small scale is used to measure (transfer) only one angle at a time.

The universal tool is used to simultaneously transfer two or three corners.

To measure or mark angles, to adjust small tools or determine the magnitude of angles transferred by them, goniometer tools with an independent angle are used. Such tools include protractors and protractors. Protractors are usually used to measure and mark angles on a plane. Goniometers are simple and universal.

Rice. 14. Simple malka and methods of its use

A simple protractor consists of a ruler 1 and protractor 2 (Fig. 15, a). When taking measurements, the goniometer is placed on the part so that the ruler 1 and bottom edge m protractor shelves 2 coincided with the sides of the measured part 3. The angle is determined by the pointer 4, moving along the protractor scale along with the ruler. A simple goniometer can measure angles with an accuracy of 0.5–1°.

Rice. 15. Goniometers: a – simple, b – optical

The optical protractor consists of a housing 1 (Fig. 15, b), in which a glass disk is fixed with a scale having divisions in degrees and minutes.

The price of small divisions is 10 ". The main (fixed) ruler 3 is rigidly attached to the body. On the disk 5 mounted magnifying glass 6, lever 4 and the movable ruler is strengthened 2 . Under the magnifying glass, parallel to the glass disk, there is a small glass plate on which is a pointer, clearly visible through the eyepiece of the magnifying glass. Ruler 2 can be moved longitudinally and using a lever 4 secure in the desired position. While turning the ruler 2 the disk will rotate in one direction or the other in the same direction 5 and magnifying glass 6. Thus, a certain position of the ruler will correspond to a very definite position of the disk and magnifying glass. Once they are secured with the clamping ring 7, observing through magnifying glass 6, read the inclinometer readings.

An optical inclinometer can measure angles from 0 to 180°. Permissible errors in optical inclinometer readings are ±5".

Straight edges are used to check planes for straightness. In the process of processing planes, rulers are most often used. They are divided into pattern rulers with a double-sided bevel, triangular and tetrahedral (Fig. 16, a).

Rice. 16. Pattern rulers: a – structural forms of rulers: double-sided, triangular, tetrahedral, b – method of applying a ruler

Pattern rulers are manufactured with high precision and have thin ribs with a radius of curvature of 0.1–0.2 mm, thanks to which it is possible to very accurately determine the deviation from straightness using the light slit method (through transmission). To do this, the ruler is installed with its edge on the surface of the part being checked against the light (Fig. 16, b). Any deviations from straightness will be noticeable between the ruler and the surface of the part. In good lighting, deviations from straightness of up to 0.005-0.002 mm can be detected. Pattern rulers are made from 25 to 500 mm in length from carbon tool or alloy steel with subsequent hardening.

Storage and care of measuring instruments. The accuracy and durability of the instrument depend not only on the quality of workmanship and skillful handling, but also on proper storage and care.

The simplest measuring tool is usually stored in a workbench drawer, where it is arranged in a certain order by tool type and size. Calipers and measuring rulers are stored in special cases with lockable lids. To protect instruments from rust, lubricate them with a thin layer of pure technical petroleum jelly, after wiping them well with a dry cloth. Before using the tool, remove the lubricant with a clean cloth or by washing it in gasoline. If rust stains appear on the instrument, it must be placed in kerosene for a day, then rinsed with gasoline, wiped dry and lubricated again.

Any production involves the use of them. They are also necessary in everyday life: you must admit, it is difficult to do without the simplest measuring instruments during repairs, such as a ruler, tape measure, calipers, etc. Let's talk about what measuring instruments and devices exist, what they are fundamental differences and where certain types are used.

General information and terms

A measuring device is a device with the help of which the value of a physical quantity is obtained in a given range, determined by the scale of the device. In addition, such a tool allows you to translate values, making them more understandable to the operator.

The control device is used to monitor the technological process. For example, this could be some kind of sensor installed in a heating furnace, air conditioner, heating equipment, and so on. Such a tool often determines properties. Currently, they produce a wide variety of devices, including both simple and complex ones. Some have found their application in one area, while others are used everywhere. To understand this issue in more detail, it is necessary to classify this tool.

Analog and digital

Instrumentation and instruments are divided into analog and digital. The second type is more popular, since various quantities, for example, current or voltage, are converted into numbers and displayed on the screen. This is very convenient and the only way to achieve high accuracy of readings. However, it is necessary to understand that any digital instrumentation includes an analog converter. The latter is a sensor that takes readings and sends the data to be converted into a digital code.

Analogue measuring and control instruments are simpler and more reliable, but at the same time less accurate. Moreover, they are mechanical and electronic. The latter differ in that they include amplifiers and value converters. They are preferable for a number of reasons.

Classification according to various criteria

Measuring instruments and devices are usually divided into groups depending on the method of providing information. Thus, there are recording and display instruments. The first are characterized by the fact that they are able to record readings in memory. Recording devices are often used that independently print data. The second group is intended exclusively for real-time monitoring, that is, while taking readings, the operator must be near the device. Also, control and measuring instruments are classified according to:

• direct action - one or more quantities are converted without comparison with the same quantity;
• comparative - a measuring instrument designed to compare the measured value with an already known one.

We have already figured out what types of devices there are in the form of readings (analog and digital). Measuring instruments and devices are also classified according to other parameters. For example, there are summing and integrating, stationary and switchboard, standardized and non-standardized devices.

Measuring locksmith tools

We encounter such devices most often. The accuracy of the work is important here, and since a mechanical tool is used (for the most part), it is possible to achieve an error of 0.1 to 0.005 mm. Any unacceptable error leads to the need for regrinding or even replacement of the part or the entire assembly. That is why, when fitting a shaft to a bushing, a mechanic uses more precise tools rather than rulers.

The most popular plumbing measuring equipment is a caliper. But even such a relatively accurate device does not guarantee a 100% result. This is why experienced locksmiths always take a large number of measurements, after which they select If more accurate readings are required, they use a micrometer. It allows measurements down to hundredths of millimeters. However, many people think that this instrument is capable of measuring down to microns, which is not entirely true. And it is unlikely that such precision will be required when carrying out simple plumbing work at home.

About protractors and probes

It is impossible not to talk about such a popular and effective tool as a protractor. From the name you can understand that it is used if you need to accurately measure the angles of parts. The device consists of a half-disk with a marked scale. It has a ruler with a movable sector on which a vernier scale is applied. A locking screw is used to secure the movable sector of the ruler to the half-disk. The measurement process itself is quite simple. First, you need to attach the part to be measured with one edge to the ruler. In this case, the ruler is shifted so that a uniform gap is formed between the edges of the part and the rulers. After this, the sector is secured with a locking screw. First of all, readings are taken from the main ruler, and then from the vernier.

Often a feeler gauge is used to measure the gap. It is a simple set of plates fixed at one point. Each plate has its own thickness, which we know. By installing more or fewer plates, you can measure the gap quite accurately. In principle, all these measuring instruments are manual, but they are quite effective and it is hardly possible to replace them. Now let's move on.

A little history

It should be noted when considering measuring instruments: their types are very diverse. We have already studied the basic instruments, and now I would like to talk about a little about other instruments. For example, an acetometer is used to measure strength. This device is capable of determining the amount of free acetic acid in a solution, and was invented by Otto and was used throughout the 19th and 20th centuries. The acetometer itself is similar to a thermometer and consists of a 30x15cm glass tube. There is also a special scale that allows you to determine the required parameter. However, today there are more advanced and accurate methods for determining the chemical composition of a liquid.

Barometers and ammeters

But almost every one of us is familiar with these tools from school, technical school or university. For example, a barometer is used to measure atmospheric pressure. Today liquid and mechanical barometers are used. The first ones can be called professional, since their design is somewhat more complex and the readings are more accurate. Weather stations use mercury barometers because they are the most accurate and reliable. Mechanical options are good for their simplicity and reliability, but they are gradually being replaced by digital devices.

Instruments and measuring instruments such as ammeters are also familiar to everyone. They are needed to measure current in amperes. The scale of modern instruments is graded in different ways: microamperes, kiloamperes, milliamperes, etc. They always try to connect ammeters in series: this is necessary to lower the resistance, which will increase the accuracy of the readings taken.

Conclusion

So we talked to you about what control and measuring tools are. As you can see, everyone is different from each other and has completely different scope of application. Some are used in meteorology, others in mechanical engineering, and still others in the chemical industry. Nevertheless, they have the same goal - to measure readings, record them and control quality. For this purpose it is advisable to use precise measuring instruments. But this parameter also makes the device more complex, and the measurement process depends on more factors.

The measuring tool is used to determine the parameters of parts. Experts distinguish between universal, scale, precision, and scaleless control and measuring instruments and devices.

Ruler, meter, protractor - these are the main universal units designed to determine various parameters (length, width). If it is necessary to measure individual elements of a part, then additional construction tools are used (thicknesser, calipers, bore gauge). The choice of device depends on the type of work to be done. Experts distinguish the following types of measuring instruments:

• workers (used in workshops);
• control (check working devices).

When carrying out measuring work, you can get an inaccurate result. This is due to the imperfection of marking tools and the measuring method used. The deviation of the obtained value from the actual value is an accurate measurement, and the magnitude of the deviation is the degree of accuracy of the measurement.

To obtain reliable results, it is recommended to use high-quality testing and measuring instruments. A steel ruler can be used to determine very short lengths. This device allows you to obtain a measurement accuracy of 0.25-0.5 mm.

If it is necessary to measure a long distance, then use a steel or wooden hand-held measuring tool. Steel meters are presented in the form of tape measures. Unfortunately, the hinge joint of such devices quickly becomes loose. In this case, the measuring instrument will need to be repaired. Experts recommend measuring parts using a tape measure (length 1-2 m).

To accurately determine the length or diameter, use a caliper or caliper gauge. This measuring and marking tool consists of a rod, movable and fixed jaws, and a slider. If necessary, you can use a caliper with a depth gauge. The last part of the tool is located on the jaw frame.

Specifications

A micrometer is used to carry out measuring work with an accuracy of up to 0.01 mm. By rotating the sleeve, the spindle is set to the required value. A division scale is provided on the tube and sleeve. A micrometer gauge is used to determine the diameter of the hole. Experts include the following main parts of the device:

• sleeve;
• tip;
• tube with division scale.

Tools for marking and measuring angles include a protractor. Such a device is made with or without a vernier. The angle is measured with an accuracy of 2 degrees. A carpenter's tool for measuring angles consists of a half-disk with a ruler and a square. The devices of the Caliber plant are an arc with a degree scale along which a vernier and a plate move. The last part is equipped with a holder with which the square and ruler are fixed. The degree scale is designed for 130 degrees. Carpentry tools are used to mark angles from 0 to 320 degrees (while maintaining an accuracy of 2 degrees). To calculate the angle, take into account which divisions the zero is located between.

Bore gauge and caliper are auxiliary marking tools that are used to determine various quantities by transferring the size from the measuring device to the product, or vice versa. A caliper is a carpenter's marking tool. Its legs are connected to each other by hinges.

A surface thicknesser is a precision measuring device that is used when drawing parallel lines on a part or to mark and measure inaccessible parts of a part using other devices. The device stand is mounted on a special stand.

Additional devices

To determine the thread pitch, experts advise using a set of thread gauges. You will first need to select the comb profile to the angle of the thread profile. If necessary, additionally measure the outer diameter of the product. To do this, use a caliper. If the data obtained coincides, then the number of threads or pitch is determined correctly. To make accurate measurements, an instrumental microscope is used.

• functionality (calculation of room area, built-in calculator, measurement memory);
• reliability;
• repair;
• high measurement accuracy (1.5-2 mm);
• long distance measurement (up to 200 m).

The laser tape measure is equipped with an optical or digital sight, level and inclinometer. For carrying out measuring work, experts recommend using only serviceable devices. If necessary, the controller of measuring instruments and special tools will calibrate and check the technological equipment of the measuring instruments. Experts identify the following methods for checking marking tools:

• without using comparison tools;
• comparison of the used unit with a model analogue using a comparator;
• direct and indirect measurement.

Initial verification is carried out after production and repair of the device.

Each instrument in use undergoes periodic verification.

To confirm the suitability of the product, an extraordinary verification is carried out.

To control the quality of the primary or periodic methodology, inspection verification is performed. This procedure is carried out by state supervision or departmental control.

If necessary, the measuring instrument is repaired. To control a measuring instrument for its suitability for use in world practice, calibration is used. In a special laboratory, measuring instruments are calibrated to determine and confirm their characteristics and functions. The result obtained is certified by the appropriate sign (it is applied to the measuring device) or by a certificate and an entry in the operational documentation.