Principle and method of measurement. General methods of measurement. What are the measuring instruments

It is difficult to overestimate the significance of measurements in the life of modern man. As technology develops, the question of the need for them is not at all worthwhile, but the principles and methods that allow to increase the accuracy of measurements come to the fore. The range of areas in which systems and methods of measurement are involved are also expanding. At the same time, not only technical and technological approaches to the implementation of these operations are developing, but also the concept of their application. To date, the method of measurement is a set of techniques or techniques that allow one or another principle of determining the sought value to be realized.

Principles of measurement methods

At the heart of any measurement method lies a certain physical law, which, in turn, is based on this or that natural phenomenon. In metrology, physical phenomena are often defined as effects that cause regularity. To measure different values, specific laws are applied. For example, the current is measured by the Josephson effect. This phenomenon, in accordance with which the superconducting current passes through an interlayer of dielectrics separating superconductors. To determine the characteristics of the absorbed energy, another effect is already being applied - Peltier, and for calculating the speed - the law of change in the frequency of radiation, discovered by Doppler. In a simpler example of determining the mass of an object, gravity is used, which manifests itself in the weighing process.

Classification of measurement methods

Usually, two characteristics of the separation of measurement methods are used - by the nature of the changes in quantities versus time and by the method of obtaining the data. In the first case, statistical and dynamic methods are distinguished. Statistical methods of measurement are characterized by the fact that the result obtained does not change depending on when they are applied. This can be, for example, the main methods of measuring the mass and size of the object. Dynamic methods, on the contrary, initially allow the possibility of fluctuations in the indicators. These methods can include those methods that allow you to monitor the characteristics of pressure, gas or temperature. Changes usually occur under the influence of environmental media. There are other classifications of methods, due to the difference in the accuracy of the measurements and the conditions of the operation. But they are, as a rule, of a secondary nature. Now we should consider the most popular measurement methods.

Comparison method with measure

In this case, the measurement is due to the comparison of the sought value with the values reproduced by the measure. As an example of this method, we can calculate the mass using the lever- type weights . The user initially works with a tool in which certain values with measures are laid. In particular, using the system of balance with weights, it can fix with a certain degree of accuracy the weight of the object. A classic instrument for measuring pressure, also in some modifications, presupposes a determination of the value by comparison with the indications in a medium in which the initially known quantities already act. Another example concerns the measurement of the voltage. In this case, for example, the performance of the compensator will be compared with the known electromotive force of the normal element.

Measurement method of the complement

Also a fairly common technique that finds application in a wide variety of fields. The method of measuring the value of the complement also provides for the desired value and a certain measure, which is known in advance. Only, unlike the previous method, the measurement itself is made when comparing not with the calculated value, but in the conditions of its addition by an analogous value. As a rule, methods and measuring instruments on this principle are more often used in working with physical indicators of the characteristics of the object. In a sense, with this technique, the acceptance of determining quantities through substitution is similar. Only in this case the correction factor is provided not by a value that is analogous to the desired value, but by the readings of the reference object.

Organoleptic method of measurement

This is a rather unusual direction of metrology, which is based on the use of human senses. There are two categories of sensory measurements. For example, the elementwise method makes it possible to evaluate a specific parameter of an object without giving a complete picture of its characteristics and possible operational qualities. The second category represents a complex approach, in which the method of measurement with the help of the senses gives a more complete picture of the different parameters of the object. It is important to understand that complex analysis is often useful not only as a way to account for a whole group of characteristics, but rather as a tool for assessing the overall suitability of an object in terms of possible use for a particular purpose. With regard to the practical application of organoleptic methods, with their help one can evaluate, for example, the ovality or the quality of faceting of cylindrical parts. In a complex measurement by this method, one can get an idea of the radial runout of the shaft, which will be revealed after the analysis of the same ovality and the characteristics of the outer surface of the element.

Contact and non-contact measurement methods

Principles of contact and non-contact measurement have a significant difference. In the case of contact devices, the value is fixed in close proximity to the object. But, since this is not always possible due to the presence of aggressive media and difficult access to the place of measurement, the non-contact principle of calculating the values has become widespread. The contact method of measurement is used in determining such quantities as mass, current strength, dimensional parameters, etc. However, when measuring extremely high temperatures it is not always possible.

Non-contact measurement can be performed by special models of pyrometers and thermal imagers. In the process of work, they are not directly in the target measurement medium, but interact with its radiation. For a variety of reasons, the methods of measuring temperature by the non-contact principle are not very accurate. Therefore, they are only used where it is necessary to have an idea of the characteristics of certain zones or areas.

Measuring instruments

The range of measuring instruments is very extensive, even if we speak about a specific area separately. For example, thermometers, pyrometers, the same thermal imagers and multifunction stations with the functions of a hygrometer and a barometer are used to measure temperature alone. To take into account the humidity and temperature readings in the complex, loggers equipped with sensitive probes have recently been used. In assessing atmospheric conditions, a pressure gauge is often used, it is a device for measuring pressure, which can be supplemented by sensors for monitoring gaseous media. A wide group of devices is also represented in the segment of means for measuring the characteristics of electric circuits. Here you can identify such devices as a voltmeter and an ammeter. Again, as in the case of meteorological stations, the means for taking into account the parameters of the electric field can be universal, that is, taking into account several parameters simultaneously.

Instrumentation and automation

In the traditional sense, a measuring instrument is a tool that gives information about a particular quantity characteristic of a particular object at a given moment. During the operation, the user records the readings and then makes the appropriate decisions based on them. But increasingly these same devices are integrated into a set of equipment with automation, which, on the basis of the same recorded indications, independently makes decisions, for example, on the correction of operating parameters. In particular, instrumentation and automation of equipment are successfully combined in gas pipeline systems, in heating and ventilation systems, etc. For example, taking into account the pressure in the pipeline will signal the automatic system about increasing or increasing the volumes of supply of the working medium-water or the same Gas.

Measurements and errors

Virtually any measuring process to a certain extent involves the assumption of a deviation in the provided results relative to the actual values. Accuracy can be and 0,001%, and 10%, and more. In this case, random and systematic deviations are identified. The random error in the measurement result is characterized by the fact that it does not obey a certain regularity. Conversely, systematic deviations from actual values differ in that they retain their values even with numerous repeated measurements.

Conclusion

Manufacturers of measuring instruments and highly specialized metrology equipment are striving to develop increasingly functional and at the same time accessible models. And this concerns not only professional equipment, but also household products. For example, current measurement can be performed at home using a multimeter that captures several parameters simultaneously. The same can be said about devices that work with readings of pressure, humidity and temperature, which are endowed with a wide range of functions and modern ergonomics. However, if there is a task of registering a specific value, experts still recommend accessing special devices that work only with the target parameter. As a rule, they have higher accuracy of measurement, which is often of decisive importance in assessing the performance of the equipment.