Measuring instruments

Among the most common measurement instruments include calipers, shtangenglubinomer, micrometer and nutrometr. All of them can get fairly accurate results, but even with good tools there is some measurement error. As a rule, its value is indicated in the data sheet, and that it directly affects the value of the instrument. The lower the error, so, consequently, higher accuracy, which means that the price may differ significantly from the price of a simple model of the same calipers or a micrometer. Measurement error Even if you use the most expensive measuring instrument, we can not exclude the possibility of error. The main causes that lead to inaccuracies in measurement are the inability to use the tool, use a damaged instrument (including with whipped the zero mark on the scale), the contamination of working surfaces of the instrument and of the measured object, the measurement of hot or cold items. It is therefore very important to keep measuring instruments in a protective case, promptly remove them from pollution, to verify that the original mark on a scale of zero. Standard temperature at which the measurements are carried out parts (especially metal), is considered to be +20 ° C. Another way to reduce errors is to conduct a series of measurements of one parameter and calculating the arithmetic mean value. This practice is widely applied using inexpensive tools, it did not interfere in the measurement and professional models, whose error is extremely small. Vernier scale, to improve the accuracy of measurements, some instruments are equipped with auxiliary scale. It is called differently: vernier - in honor of the Portuguese mathematician P. Nunes, or Vernier - after the French scientist P. Venier, in 1631 proposed the construction of a scale that is used to this day. The operating principle of this device is based on the fact that the eye captures better match major and minor divisions of the scale, what determines the mark between the divisions. Moreover, the zero vernier indicates the integer part, and the number of divisions, coinciding with the division of main scale - on a fractional. Application of vernier allows to obtain results with an accuracy of tenths to hundredths of a millimeter. Caliper Caliper is a tool consisting of stiff metal ruler (rods), borders with vernier measurement and sponges. Rod has a layout with a scale division of 0.5 mm, and the vernier - 0,02 mm. To fix the risks to the lineup is a special screw. Measuring jaws are divided into upper and lower. The first are used for internal measurements (basically, it's the hole in the details), the second - to get the external dimensions of the products. Work with a caliper is quite simple. Lower measuring sponges farmed in hand, between them is part and then shifted to lock lips. To measure the inside details of the upper jaws are moved, are introduced into the hole of the measured and there are disclosed. When working with calipers important to keep the tool perpendicular to the details to fit snugly to the sponge surface shall be measured. The results of measurement are determined by the main scale and vernier. In addition to conventional calipers, there are electronic models of the tool, leading out the value of measurement on the scoreboard. Shtangenglubinomer As the name implies, shtangenglubinomer designed to measure the depth of the grooves, but with his own help determine the height of the ledges. The tool consists of a rod with a marking, the scope of Vernier and screws. Working part shtangenglubinomera rod is introduced into the groove of being measured, the frame is lowered until it stops and recorded, and then withdrawn testimony. Price division frames, like calipers, 0.5 mm, vernier - 0,02 mm. Micrometer Micrometer is designed to measure the surfaces of small sizes (up to two mikromillimetrov). This tool can be called a professional, as in life, it almost does not apply. Micrometer consists of a bracket with the heel, rolling screw with a very fine thread, ratchet, sockets, stem, having two scales - the top indicates the size in millimeters, the bottom - in half a millimeter. In addition, the conical part of the drum, which rotates around the hub-stem, is a Vernier: it applied 50 divisions, which serve to count hundredths of a millimeter. Measuring surface of the tool is the butt of the micrometer screw, and such a feature as a rattle, provides a constant axial force when in contact with screw detail. Because of the complexity of manufacturing the screw with a precise step at great length in several micrometers run sizes: for measuring lengths from 0 to 25 mm, 25 to 50 mm, 50 mm to 75 mm, etc. Measurement technique with a micrometer as follows: the product is clamped between the heel and the screw, then remove the evidence. Scale is usually equal to 0.5 or 1 mm, the drum has a 50 or 100 divisions for the reference with an accuracy of 0,01 mm. But there are also more accurate readings of the micrometer with 0.005, 0.002 and 0.001 mm. According to the principle of distinction and manual desktop mics, and depending on the design and purpose of these tools are divided into smooth, lever, sheet, pipe, rezbomernye with inserts and zubomernye. Callipers callipers - an instrument for very precise measurement of the size of holes, slots and internal surfaces. The most widely used indicator and micrometer calipers. Indicator caliper can measure the hole diameter of 6 mm or larger. Price dividing tool is 0.01 mm, the error readings - from 0,15 to 0,025 mm. This caliper consists of two parts: a measuring device and dial gauge type (flat head). It has two scales: a large scale division of 0.01 mm and the total turnover of the arrows 1 millimeter and a small, showing the number of revolutions of the big hands, that is millimeters. Proceedings of the rod heads - 10 mm, but a set of adjustable rods can increase the range of sizes. For measurements is necessary to choose adjustable rod of suitable length and screw it into the caliper. Then tipped instrument is introduced into the measured hole, set perpendicular with an easy rocking, after which point deflection from zero. If the arrow "goes" to the right - the measured amount is less than the configured, if the left - more. Thus, when the prescribed amount, for example, 10 mm when the needle swings to the right by 12 divisions, it will be 10 - 0.12 = 9.88 mm, if the left - the size of the hole 10 + 0.12 = 10.12 mm. When using the calipers need to keep it only for the wooden sleeve without touching the rod: by heating the metal arm detail lengthened by a few hundredths of a millimeter, and exactly that number makes a mistake when measuring tool. To verify the precise holes using micrometer calipers with a scale division of 0.01 mm and an accuracy of reading no less than ± 0,006 mm. Micrometer calipers, also called shtrihmassom, designed to measure the internal dimensions of the absolute method. It comes with outside dimensions of 50 mm to 75 mm, 75 mm to 175 mm, 75 mm to 600 mm, from 150 to 1250 mm, from 860 to 2500 mm and from 1520 to 4000 mm. Micrometer caliper consists of a stalk pressed into it a spherical measuring tip of the micrometer screw, a drum rigidly connected to a micrometer screw, cap, securing the drum on the micrometer, a measuring tip, safety cap and stopper. When you use micrometer caliper to install it exactly perpendicular to the axis of the measured holes, for which one end of the need to rely on the edge of the hole, and another move in the diametrical plane, just as is done in the measurement instrument indicator type. Thumbscrew, the same as that of the micrometer for outdoor measurements, allows measurements up to 0.01 mm, and the readings being taken in the same way as with a micrometer. All the tools discussed above apply when you need to know the dimensions of parts or holes up to hundredths of a millimeter. And if in the home such values ??are needed infrequently, is for professionals who work every day with the exact data, a good measuring tool - half the success.