DIY electronic caliper repair

The main defects of a vernier tool, which can be eliminated during repair, are errors in vernier divisions, curvature of the rod guide rib, pitching and skewing of the frame, non-parallelism of the measuring surfaces, their damage, wear of the base, etc.

Checking the correctness of the ribs of the rod and measuring planes of the jaws is carried out using blocks of end measures clamped between the measuring planes when moving the frame every 10 mm of the rod length. In any position of the frame on the rod, the pressure force of the measuring planes on the block must be the same over the entire plane of the measure. If the touch of the measuring planes with any block for sharp and blunt jaws is different in different positions of the frame, this means that the rod is bent. If, at any position of the frame, the solution of sharp sponges is less than the solution of blunt ones, or vice versa, then the jaws of the caliper are faulty.

To fix the barbell, its working edge is checked for paint on a test plate, and the bulges are removed with a personal file or debugging. Then the second edge of the bar is made strictly parallel to the working edge, also using a file or finishing. After that, the measuring planes of the jaws are fine-tuned.

To fine-tune them, the caliper is fixed in a vice with lead jaws (Fig. 177, a). Lapping is carried out with a cast iron lapping (Fig. 177, b). The lap is clamped between the jaws, for which the frame is brought close to the lap and the micrometric feed of the frame is fixed. The lap should effortlessly move back and forth between the jaws.

FIG. 177.
Finishing the caliper jaws.

The misalignment of the jaws is not difficult to establish. To do this, it is enough to clamp the block of end measures between the jaws and if one of the sides of the block moves away from one of the lateral sides of the jaws, then the skew is established. The misalignment of the working planes of the jaws with respect to the rod is corrected by grinding on a surface grinding machine. After grinding, sharp and dull sponges are polished with a coarse GOI paste at the same time and polished with glass laps with a thin paste. The lapping of the jaws is considered complete if the lapping passes with the same force at both ends.

After finishing the jaws, check the coincidence of the zero division of the rod with the zero division of the vernier. To do this, the jaws are tightly shifted and clamped on the movable frame of the caliper. After making sure that there is no gap between the jaws, release the screws holding the frame with the vernier. Then the frame with the vernier is moved to one side or the other in such a way that the first and last divisions of the vernier exactly coincide with the first and other corresponding divisions of the bar. Also pay attention to the fact that the second and third risks from the beginning of the vernier are located equally with the second and third risks from the end of the vernier in relation to the corresponding risks on the bar. After that, the screws are fixed and, having checked again the coincidence of the divisions, the installation of the vernier is considered complete. In the event that when installing the vernier it is not possible to move it due to the gap in the screw holes, the holes are expanded using a file.

Very often the caliper jaws break. When correcting this defect, one of the three decisions shown in FIG. 178: shorten the length of the jaws (Fig. 178, a), remove one pair of jaws (Fig. 178.6) or make a cutout to insert a new jaw (Fig. 178, c). Sometimes a new one is welded in place of a broken sponge.

FIG. 178.
Repair and restoration of caliper jaws.

Correction of defects in lightweight calipers is carried out mainly by straightening with subsequent fine-tuning of the measuring planes. So, if even with the wear of the working surfaces of the jaws, the zero stroke of the vernier does not coincide with the zero stroke of the rod, then after finishing the measuring planes this error will be even greater.

Therefore, it is corrected by straightening. The stationary sponge is placed on a hardened block, fixed in a vice, and hit on it in place a (Fig. 179) so that its nose moves down. The blows are made on both sides of the caliper. The same is done with the sponge of the movable frame, hitting it in place b. The sharp ends of the jaws are straightened in places a and b.

FIG. 179.
Repair of a lightweight caliper (arrows show the places of impacts during straightening).

After straightening, the measuring planes are cut and brought to coincide with the divisions of the rod and the vernier, and finally the nicks are cleaned and all planes are polished with fine sandpaper.

Correction of the base of the height gauge is carried out by lapping on a lapping plate using grinding powders.

About two months ago I bought a caliper, but I was not happy for long.
Became buggy:

- you stand out as it should be “0”, and then if you move the slider several times from minimum to maximum and back, then “0” gets lost, moreover, negative values ​​appear;

- sometimes auto power off does not work.

Who can meet with such a defect and will tell you how to treat it.

But the main thing you did not see, namely, negative values ​​do not exist in linear dimensions.

Thanks also for the button - I explained, but again I did not see that in my post I directly indicate that I am setting “0”, this action consists of two operations: - first you bring the lips down to “0”, and then, if necessary, you hammer on the ZERO button.

You say: “There is no need to“ drive the engine from minimum to maximum and back ”several times, and then to establish a malfunction. Negative values ​​appear after 2-3 movements.

How can there be no negative ones with a linear one ?! Look, even in the photo above.

How does the sensor work on the subject? can kakraz through a quick "insertion" is buggy? The device is not designed for measuring amplitude values. Dertur too quickly - the sensor forgave with a mistake. After all, the report is not based on the absolute value of the distance, but, for sure, according to the number of sensor pulses with a bristle from zero.
You can clean the working element of the sensor. Although, IMHO, you are simply not using it for its intended purpose.

So weakly strain the pumpkin, where are they found in nature, can you tell me?

Write that some kind of capacitive dependence. this infa is visible on the photo.

According to TD, the speed of movement of the engine is 1.5 m / s

Yes, in the main, nails have to be hammered into a concrete wall

It's still tight with the entity: as an option, write with an error of more than + - 0.1 mm, remove the slider, and blow it with clean compressed air.

In the limit, everything converges, the bar shows minus 10 mm, and this value is variable.

But what is a slider is a mystery to me

This device is used to measure internal and external measurements, as well as between the surfaces of parts, it is used to measure the depth of holes and protrusions. An electronic caliper has a very useful function compared to a mechanical caliper - it adjusts to zero at any point on the scale, so you can observe deviations in each area of ​​the size. That is, you can set it to zero in a size of, say, 21.55 mm, and count the length from it.

In modern high-precision mechanical production, you cannot do without this convenient tool, where the measuring range is universal. In heavy and light industry, construction, and in all other branches of technical life, it is no longer possible to imagine work without using a digital caliper. If necessary, a computer can be connected to the ESH, to which all data will be displayed during the dimensional control.For this, the digital caliper has a special connector:

The digital vernier caliper has a resolution of 10 microns with an accuracy of 30 microns. This accuracy is achieved by using capacitive sensors. Capacitive sensors are very linear and protected from mechanical and electronic interference. However, they are sensitive to liquids. Accidentally trapped liquid will unbalance the measuring bridges of the plates and increase the capacity.

To begin with, we will work on this measuring device and see how it works from the inside.

The principle of its operation is a capacitive digital vernier, here is the technical documentation about its work. The digital caliper is based on a capacitive matrix - an encoder.

An electronic vernier caliper uses multiple plates to form a capacitive array that can accurately sense movement. There is a stator and a slider ("rotor") plate. The stator is in a metal ruler. And the movable part with the LCD screen has a slider.

The stator template is fabricated into a top layer of copper standard glass epoxy laminate and glued to a stainless steel caliper bar. The slider pattern, shown similarly fabricated on a PC laminate, drives a 100 kHz signal across the sin / cos plate of the stator electrodes and picks up an alternating voltage across the two center pickup plates that describe the sin (displacement) and cos (displacement) signals.

As you will see in this article, modifying an electronic digital caliper is a very simple procedure, but it must be done carefully so as not to damage the instrument. The design of the electronic caliper provides 4 special contacts. These contacts, for example, can be used to connect an external power supply, monitor functions, etc.

The pin assignments are as follows (from left to right): negative terminal, data, clock and positive terminal.

To activate the hidden options of the electronic digital caliper, you must connect pins 2 and 4 together.

There may be some differences between different electronic calipers, but in general they are modified in the same way.

The first step in reworking is finding the screws holding the case together. On our caliper, they are located under a plastic sticker. Their location can be seen in the photograph.

After opening the plastic case containing the PCB, display, and some metal parts, you need to unscrew a few screws to remove the PCB.

Take extra care when handling the printed circuit board and display.

The display is connected to the printed circuit board via a conductive rubber gasket. Be careful not to disconnect the display from the board as this will make it difficult to align the connections during assembly. And if the location is incorrect, the display may turn off spontaneously and strange characters may appear on it.

After removing the printed circuit board of the electronic caliper, we get access to the necessary contacts.

Now you can solder 2 thin wires (the thinner the better). Solder one to pin number 2 and the other to pin number 4.

The best way to short-circuit these terminals is to use a micro button, such as from an old computer mouse. The pins of the button must be bent at an angle of 90 º (as in the picture) so that it fits snugly into the slot and, therefore, is firmly held in place.

After soldering the wires, the assembly of the electronic digital caliper is carried out in the reverse order. After assembly, the soldered wires should stick out from the socket.

After that, we solder the button and place it in the slot.

Since the legs of the button have been pre-bent, they spring the button and it is held firmly in place. This is what it looks like.

By pressing a new button, we get access to some modes that were previously not available.

When the button is pressed for the first time, the electronic vernier caliper enters the fast reading mode (FT), when the “ZERO” button is pressed, we can freeze the measured value (H).

When the button is pressed again, the electronic vernier caliper enters the MIN mode. In this mode, the display shows the smallest measured value.

If you press the "ZERO" button again, we will again switch to the mode of fixing the measured value (H).

When the button is pressed again, the electronic vernier caliper will enter the maximum value (MAX) mode. In this mode, the display shows the highest measured value.

If you press the "ZERO" button again, we will again switch to the mode of fixing the measured value (H).

The electronic digital caliper modified in this way reveals all its functionality and capabilities.

It just so happened (at least for the author) that the accuracy of measurements is made: with a ruler up to centimeters and a half, calipers up to millimeters, but tenths and hundredths of a millimeter are "caught" exclusively with a micrometer. What prevents to use a vernier caliper to measure tenths of a millimeter, because it is for this, and is intended, "offhand" will be difficult to answer. Often, even those who know the device of this measuring tool will be careful to indicate the size fixed with a caliper with an accuracy of ten - because the scale (vernier) is small in nature, "responsible" for determining tenths of a millimeter. I admit that it is for this reason that some of the calipers began to be produced equipped with a dial scale and even equipped with an electronic display (electronic).

And what prevents you from upgrading an existing caliper and thereby bringing the accuracy of its measurements closer to the measurements of a dial and electronic measuring instrument, for example, equipping it with a magnifying glass? He sat down to the computer and began to draw the device that had already visited the imagination.

The sketch was made in a section, where the number:

• 1 - the caliper bar is marked
• 2 - movable caliper frame
• 3 - holder frame, it is installed on a movable frame
• 4 - screw securing the frame to the frame
• 5 - the screw securing the frame with the magnifying glass to the frame
• 6 - magnifying glass frame
• 7 - the spring pressing the frame to the head of the fastening screw
• 8 - magnifying glass

In accordance with the finished sketch, I collected the most suitable components of the future holder "by bottom".

In a textolite cube (in the past, some part of the housing of an electronic device, and in the future, the holder's frame), using a file, I increased the existing groove to the size corresponding to the movable frame of the caliper and drilled a 3 mm hole in the center for the fastening screw.

On the side there is a M4 threaded hole for the screw for attaching the frame with a magnifying glass. With the end of the production of the bed, time-consuming operations requiring precision and careful adjustment are completed.

A frame was made from a piece of soft plastic (in addition to the existing one). Two holes have been drilled in the plastic plate. The smaller one is for the frame fastening screw, the larger one is for the already existing frame (into which it is screwed along the thread, which makes it possible to adjust the sharpness).

The device is assembled according to the drawing. I did not specially cut the thread in the additional frame, it was made by the thread of the old (metal) frame when screwing in for the first time. For this, a soft plastic plate was selected, and the hole was made 0.5 mm less than necessary. It is clearly seen that the risks of vernier (the name of the scale for determining tenths of a mm) are increased to the size of a more comfortable observation. This makes it possible to confidently determine the measured size with an accuracy of "ten".And even more - now you can easily distinguish a wire with a size of 0.85 mm from 0.80 mm by means of measurement.

1. count the number of whole millimeters, for this they find on the bar scale the stroke closest to the left to the zero stroke of the vernier;
2. count fractions of a millimeter, for this, on the vernier scale, find the stroke closest to the zero division and coinciding with the stroke of the barbell scale - its serial number will mean the number of tenths of a millimeter;
3. add the number of whole millimeters and fractions.

The fixture is easy to install and remove and can only be used when needed. Project author - Babay iz barnaula.

Vernier tool malfunctions and checks.

The most typical malfunctions of vernier tools, as a result of which the accuracy of the readings is disturbed, are: wear of the measuring surfaces and dullness of the sharp ends of the jaws; wear and deformation of the working surfaces of the rods and the frame; skew of the main frame; incorrect installation of vernier; loosening of the spring; wear of the thread of the screw and nut of micrometric feed and a number of others. p The readings of vernier tools with a readout value and 0.05 mm are checked using end measures of length of the 2nd accuracy class (6th grade), and with a readout value of 0.1 mm - by means of end measures of length of the 3rd class.

The misalignment of the movable jaw is relatively motionless, and is also detected using a gauge block.

Having established a limit measure in two extreme positions, readings are taken and, by their difference, the value of the non-parallelism of the measuring surfaces caused by the skew of the movable jaw is judged.

The wear of the measuring surfaces is determined by the value of the discrepancy between the zero lines of the scales of the rod and the vernier with tightly shifted jaws. For vernier tools with a reading value of 0.02 and 0.05 mm, the gap between the measuring surfaces should not exceed 0.003 mm, and for vernier tools with a reading value of 0.1 mm - 0.006 mm. In fig. 79.6 shows how with the help of gage blocks and a curvature ruler it is possible to determine the size of the gap between the measuring surfaces by eye.

The scheme for checking the wear of the working surfaces of the sponge for internal measurements is shown in Fig. 1, f. A limit measure is placed between the jaws for external measurements, and then, using another vernier tool, the distance between the jaws for internal measurements is checked. This distance must be equal to the size of the gauge block.

The rod wear is set with a curved ruler to the gleam.

Repair of caliper tools. The wear of the working surfaces of the vernier tools is eliminated by straightening the jaws with their subsequent finishing. Defects of the measuring surfaces of the jaws are also eliminated by straightening and the coincidence of the zero lines of the scales is achieved. After straightening, they begin to fine-tune the measuring surfaces of the posts with plane-parallel laps, for which the caliper is fixed in a vice, the lap is placed between the jaws, and the frame is shifted until the jaws come into contact with the lap. In this position, the Frame is fixed with a locking screw and, by moving the pri-r between the jaws with little effort, the surfaces are fine-tuned from the side of both sharp and blunt jaws until flatness, parallelism and the same size of the solution of both sides are achieved.

The straightness of the measuring surfaces is checked with a curved ruler, and the parallelism of the frame jaws to the rod jaws and the dimensions between them are controlled by end measures, while the force with which the measure is introduced between the jaws should be the same for both sides. By inserting a gage block not from the end of the jaws, but from the side along the entire plane and at the same time slightly turning it, you can determine the degree of parallelism of the surfaces. If the tile is held up by the ends of the jaws, freely rotating further along the entire surface, or has a gap in front, then the jaws are not parallel.

The outer surfaces of the blunt jaws are brought to parallelism.The size of the jaws must be an integer number of millimeters with tenths (for example, 9.8 mm). After finishing the jaws, the vernier is set to zero bar division. To do this, the jaws are shifted until the measuring planes touch and the movable frame is clamped. Then the vernier is moved until the first and last divisions coincide, while its scales must exactly coincide with the first and corresponding divisions of the bar. In this position, the vernier is fixed.

When repairing a large number of calipers, the finishing of the measuring surfaces can be mechanized. The mechanized debugging scheme is shown in Fig. 2, b. A complex zigzag movement during mechanical finishing is the result of two movements: a horizontal reciprocating movement of the lap 1 (at i = 400 d.strokes / min and a stroke length of 23 mm) and a vertical translational movement of the caliper 2 (the movement of periodic feed 5 = 1, 5-3 m / dv. Stroke. Lap). To ensure the quality of finishing, both movements are coordinated with each other. The caliper gains vertical movement only when the lap moves. At the half stroke of the lap at maximum speed, a small vertical feed is also communicated to the vernier caliper. At the extreme points of the lap path, where its speed is zero, the vertical feed of the caliper stops. The finishing pressure should be P — 2—3 kg / cm2.

When mechanically fine-tuning the caliper jaws, cast iron laps are used, caricatured with M20 micropowder.

Repair of lightweight calipers in case of jaw breakage is carried out in the following order. After the vacation in the salt bath, the worn or broken end of the sponge is cut off. Then, in the thickened part of the leg, a slot is cut with a disk cutter, the width of which is equal to the thickness of the sponge. A new sponge blank is inserted into the groove of the leg and two or three holes are drilled together, then both parts are riveted. The sponges are filed to the specified size and hardened. After cleaning, their measuring surfaces are fine-tuned.

If both jaws break, the entire upper leg is replaced with a new one. To do this, rivets are knocked out and the broken leg is removed from the bar. In the workpiece of the new leg, a rectangular window is milled and sawed, in shape and size equal to the end of the rod. Then a leg is put on the bar, the perpendicularity of its position relative to the edges of the bar is verified, holes are drilled elsewhere and the leg is riveted. The sponges are sawed off so that their configuration and dimensions correspond to the shape of the frame jaws, and then they are adjusted.

The broken sponges of the frame are replaced with new ones, for which, after knocking out the rivets and removing the unusable sponge, a blank of a new sponge is riveted in its place, filing it, hardening and finishing.

Repairing broken jaws of calipers with a stamped bar is somewhat more difficult, since the entire bar, together with the jaws, has the same thickness and it is impossible to insert a new jaw. Riveting overlays does not always provide sufficient bond strength. Welding can be used, but it is best to replace the entire top of the boom with a new stem.

For this purpose, after annealing and cutting off the jaws, the end of the ruler is milled or sawed off by hand so that shoulders are formed on the edges of the ruler, against which the leg rests. When filing the measuring planes of the jaws of the leg, it is necessary to ensure that the zero division of the vernier of the frame roughly coincides with the zero division of the scale on the ruler, since with a significant displacement of the vernier, too much metal will have to be removed at its end, which will worsen the quality of the repair.

Deformation of the rod can be caused by curvature or uneven wear of its working surface. The curvature of the rod is eliminated by straightening by bending in a vice with three narrow brass spacers.

Uneven wear of the rod is eliminated by filing and lapping on a lapping plate, controlling the straightness with a curved ruler or the paint method. Dents and nicks are cleaned with a velvet file, a touchstone and fine sandpaper with oil.

To eliminate the misalignment of the vernier with the ruler scale, it is rearranged. If the end of the vernier rests against the wall of the frame window and cannot be moved, then it is filed. At the same time, the holes for the screws are sawn, after which, by rearranging the vernier, they fix it in the correct position.

Repair of other universal measuring instruments (goniometers, height-gauges and vertical-gauge-binometers) is similar to the repair of calipers.

The main defects of the depth gauge can be the non-straightness of the reference surface, the lack of perpendicularity of the ruler relative to the reference plane and incorrect installation of the vernier.

To ensure the straightness of the reference plane of the body and the end of the ruler, they are brought together on the plate. Having extended the ruler above the plane of the body, using a curved square, check its perpendicularity relative to the reference plane.

Repair of a vernier is done in the same way as a vernier caliper. When the ruler is set to a certain size, its end is aligned with the plane of the depth gauge. In this position, the zero division of the vernier is aligned with the zero division of the ruler scale or with the division corresponding to the height of the set of gauge blocks, after which the vernier is fastened with screws.

Message # 1 KimIV »08 Oct 2015, 09:40

Product from friendly China via eBay. In the garage, I use only it for almost all measurements. Conveniently, you do not need to peer into the risks of the measuring and vernier scales, as in a vernier caliper.

On the reverse side there is some apparently useful sign

There are all the same jaws for both external and internal measurements and a depth gauge ruler.

Although the readings are accurate to a hundred square meters, I have taught myself not to pay attention to the rightmost figure, or rather to round it to ten at once. It is better to measure hundredths all the same with a micrometer. And this bar even has a passport accuracy of 3-4 hundred parts, so there is no point in catching hundreds.

Message # 2 ROW »13 Oct 2015, 10:50

The caliper can be attributed to the field of universal modern devices that have an electronic calculating device for taking readings and a digital display for displaying it. This technique, despite its relatively high cost, is a good substitute for mechanical counterparts in mechanical engineering and tool production, as well as among professionals in the private sector. They are found in repair shops and other places where there is a need to measure parts with high accuracy. Despite the fact that the micrometer has a higher accuracy class, due to the large limitations on the measuring range and less ease of use, it has not found such widespread use.

photo: electronic vernier caliper (digital) ШЦЦ

An electronic caliper can be used to obtain the outer and inner dimensions of products, and if an electronic caliper with a depth gauge, then the depth of some holes can be determined. The measuring range can be from the limit of 125 mm and more, depending on the model. As a rule, in these parameters, they completely coincide with a standard mechanical caliper. Some models are used for marking parts for technical work.

As with standard models, the digital caliper uses a direct measurement method. Thus, you can get the most accurate value of the dimensions of the workpiece clamped into the part. To obtain an accurate value for the desired type of measurement, the device has three monitoring systems. The first are the sponges for determining the external dimensions of the part.During the measurement, they clamp it, fixing it in one position, which requires some effort, and the digital display gives the measured value. The second system is jaws for measuring internal dimensions. Their measuring surfaces are located on the other side and to measure them it is necessary to spread them all the way to the surface of the walls of the workpiece in order to obtain the actual value of the dimensions. The third system is the depth gauge, which is designed to plunge into parts. This is a metal rod, the end of which must rest against the bottom to determine the depth of the product.

It should be noted right away that all systems move simultaneously and in direct proportion to the scale value. Electronic caliper can measure values ​​with an accuracy of 0.1; 0.05 and 0.01 mm, depending on the specific model. In any case, the results are displayed instantly, so you do not need to calculate everything on the Vernier scale for a long time. These products are manufactured in accordance with GOST 166-89.

The undoubted advantage is that the dial caliper immediately displays the values ​​obtained. In the production area, this is an irreplaceable property, since the speed of work there is of great importance. It also makes the work environment easier for beginners as there is no need to learn further how to use a mechanical caliper. Due to the presence of several measuring systems, the device can be used in completely different areas, since few other devices are capable of simultaneously measuring depth, internal and external dimensions, especially with such a high accuracy class. Product dimensions are usually relatively small, which is reflected in its weight. Thus, when using in hard-to-reach places, there is no inconvenience. The electronic vernier caliper has some additional functions, such as "remembering the last data", "converting values ​​from the metric system to inch and vice versa", "connecting to external devices for data transmission" and so on.

The operation of an electronic caliper depends on a power source, which can sometimes make the device ineffective at the most inopportune moment. Also, the cost of the tool is much higher than that of mechanical counterparts, which translates them into a sphere of predominantly professional use. Electronic vernier caliper 150 mm is very sensitive to vibrations, mechanical shock, drops and high humidity, since all this affects the operation of the electronic reading device, which may fail. Software glitches can also render the instrument inoperable.

photo: device of digital caliper ШЦЦ

The basic elements of the device are the same as those found in standard mechanical models, but there are still a few electronic parts. In general, Electronic Vernier Caliper 150 consists of:

• Sponges for external measurements control;
• Sponges for control of internal measurements;
• Tool bar;
• Movable frame;
• Battery;
• Length change roller;
• Zero key;
• Off / on;
• Switching mm / inch

The presence of buttons on a digital device and additional functions depends on a specific model, since some of them have modules for wireless data transmission, and there are also corresponding interfaces for connecting to a computer. Otherwise, the basic details are almost the same in all models.

The principle of operation of the device is based on the use of digital vernier. It uses a capacitive matrix with an encoder. In other words, two standard capacitors are used here, which are connected in series, with the top plate acting as a common electrode. Several plates are used here to form a capacitive array. This helps to accurately feel all movements of the sensor. The slider acts as a rotor.The stator is located in a metal ruler. On the movable part there is a screen with a slider.

In practical application, the ShTsTs caliper is not much different from other types, since here it is required to move the jaws from the zero position to the limit in order to fix the position of the part, applying some effort for the accuracy of the readings. The distance separating the position when it is abutted against the surface of the measurement part will be its size.

During the production work for the release of parts, constant control over the dimensions of the final products is required. If the ramps should be recorded in tenths and hundredths of a millimeter, then an electronic caliper will be indispensable. To operate it in the best possible way, it requires knowledge of the basic details as well as the principle behind the calculations. This is what will be discussed in the article, as well as tips for buying the best unit.

At first glance, a caliper seems to be both simple and complex at the same time. It looks a bit like a regular ruler, but has a few shifting parts. This makes the caliper suitable not only for checking the length of the workpiece, but also its diameter. Which is very important in the turning business. In addition, at one of the ends of the caliper there is a stem, which is recessed into the hole, which makes it possible to determine its depth. The caliper got its name due to the presence of a graduated ruler, which is called a barbell, and also due to the jaws, which, if necessary, can be used to describe a circle. The division on the ruler of the caliper is the same as on the lathe and is equal to 1 mm. The total length of the caliper can vary and ranges from 15 to 50 centimeters or more.

The said jaws of the caliper are at the end opposite the end of the scale from the depth gauge. They are located on either side of the bar. The purpose of some on a caliper is to measure the external, and others - the internal diameter of the parts. When measurements with a caliper have to be carried out in poor lighting or in a hard-to-reach place, then the clamp will help a lot. It is usually located on the movable frame of the caliper and is a small bolt. When tightening it, the caliper frame remains in place until it loosened up. This functionality of the caliper is especially useful if you need to transfer the dimensions from one structure to the drawing.

Everything would be simple if diameters and other quantities were always whole numbers. But most of them have a decimal remainder. To calculate the size to tenths and hundredths, there is another scale. It is called the vernier caliper scale. It is usually located on the movable frame of the caliper. On calipers, which are used for simple calculations in everyday life or in labor lessons, the vernier scale does not exceed the length of 1 cm and 9 mm. To navigate along the scale, it is necessary to move the jaws or drown the depth gauge into the required part, fix the actual size on a large scale, and then see which of the vernier divisions forms a straight line with a large scale or exactly coincides with the lower scale of the device.

Until a certain point, several types of calipers were available on the free market. Today they can be purchased in three types. Each of them has its own characteristics and methods of implementation. There are eight main groups depending on the size. It is better to purchase a caliper with a factory passport, which will indicate possible errors and methods of calibration. According to the method of determining the size of the decimal part, calipers are divided into:

• with vernier scale or SHTs;
• with a dial scale or SCCK;
• with electronic digital scale SCCTs.

The differences lie not only in the scale used, but also in the presence or absence of certain elements in the design, for example, those in which the main nodes are present are called universal. There are devices that can only measure the outer diameter. Their jaws are hard-alloyed, so they do not wear out as quickly as ordinary ones. They are designated STTs-1. There is also a vernier caliper available on the market with a lower margin of error and additional adjustment of the hundredth scale. It is designated ШЦ-2.

If you are just starting to master the process of measuring with a caliper, then the digital version can help out. Its advantage is also a high speed of measurements. The bottom line is that after converging the jaws on the parts, the final digit is instantly displayed on the digital display. There is no need to look closely at the vernier scale. As a rule, such instruments come with a full range of features, which includes reversible jaws, as well as a depth gauge. The presence of the display practically does not increase the final weight in any way. The module is not heavier than the additional scale that is present on the standard version. Advanced versions of this type of caliper have additional I / O ports, as well as a built-in converter. You can transfer the obtained values ​​to an external medium or PC with a few touches.

The electronic part of the caliper needs power. Most often, this role is played by a CR2032 battery. Although the consumption is minimal and one charge is enough for a long time, an unpleasant incident can happen and the device will sit down at the wrong time when it is necessary to take measurements. Another disadvantage is that microcircuits and electronic sensors do not tolerate vibration and shock. This means that the inaccuracy of the caliper can increase if handled carelessly. The contacts of the electrical part undergo an oxidation process from moisture, which easily disables the electronic caliper. In some cases, the converter may not work correctly, which can have far-reaching consequences in the production process. An ordinary mechanical device is devoid of all these nuances.

In fact, the electronic caliper has nothing supernatural in the principle of its functioning. The calculation is carried out in the same order as in the mechanical version, only it is automated due to the electronic vernier scale. There is a capacitive sensor inside the module. It is not the movement of the movable bar or scale that is responding. In order for it to take readings, a small discharge from the capacitors is applied to it. There are two of them in the scheme. Inside the main strip is an element that collects static electricity and transfers it to the sensor.

Which one to choose from the proposed options will depend on the application and the required level of accuracy. A digital vernier caliper may have an error of two hundredths. Therefore, if we are talking about a high-precision machine structure, then a digital caliper will be a duplicate or secondary tool, and a micrometer will come to the fore. It is capable of producing results up to a millionth of a meter. But it has its limitations. A part with a thickness or diameter of no more than 5 cm can fit between its jaws. Micrometers with a digital display have already appeared on the market, which maximally simplifies the process of taking readings during measurement. It has the same advantages and disadvantages as compared to mechanical calipers.

Before proceeding with measurements, it is necessary to inspect the caliper itself well and make sure it is working properly. The first step is to bring the sponges back to their original position. In this case, it is worth evaluating at what division the zero line is, if on the vernier scale it coincides with the starting value, then everything is fine. The surface of the sponges is visually inspected.There should be no jaggedness on them, and there should be no space between them, they should close well. It is in this case that it will be possible to talk about the minimum error and ideally accurate result in relation to the part being produced. It is desirable that the part to be measured be firmly fixed in the vice. This will prevent it from shifting in the process, which could affect the numbers. It must be placed between the working jaws and the first to be brought together. For metals and plastics, force must be applied to fit the sponges tightly. If the measurement is carried out on wood or other soft material, then excessive force will only harm.

The caliper was and remains an irreplaceable and demanded tool in most areas of production. Every self-respecting home craftsman should be able to use it and have it available. You can find domestic and foreign manufacturers on the market. Components are mostly manufactured in China, so it is better to identify the most convenient option by specific measurements.