People often encounter finding a physical quantity. In this case, they are talking about measuring something. This term comes from a science called metrology. What is a dimension?
Definition
Measurement is the process of determining a physical quantity using measuring instruments empirically. The result of the measurement process is the value in accepted units, which is called valid.
The principle of measurements is a physical phenomenon or several such phenomena that form the basis of measurements. For example, temperature measurement using the thermoelectric effect.
What is the measurement method? This is such a set of methods for using measuring instruments and their principles. And what is a means of measurement? These are the technical means that have metrological properties that meet the standards.
Types of measurements
So, what is the measurement, the definition of which is given above, is clear. But there are also types whose classification is carried out on the basis of how the measured quantity depends on the type of equation, time, conditions that determine the accuracy of the measurement results, as well as the ways in which these results are expressed.
Time dependent
Paying attention to the dependence of a quantity that is measured on time, two types of measurement can be distinguished:
- Dynamic measurements are those in which the quantity changes over time. An example would be the measurement of temperature or pressure during a gas compression process in engine cylinders.
- Static measurements are those in which the required value does not change over time. Examples: measurement of temperature, constant pressure, sizes.
Equation dependency
A method of obtaining results, which is determined by the type of equation for measurements, divides the measurements into direct and indirect, as well as joint and aggregate.
- What is a direct measurement? This is such a measurement in which the desired value of the physical quantity is found directly from the data obtained as a result of the experiment. Examples of direct measurements are: temperature measurement with a thermometer, product diameter measurement with a micrometer or vernier caliper, angle measurement with an angle meter.
- What is an indirect measurement? This is such a measurement in which the desired quantity is determined on the basis of the relationship between those quantities that are found using direct measurements and the unknown quantity. Examples of such measurements: measuring the diameter of the thread using the three-wire method, finding the body volume using direct measurements of its size. Indirect measurements are very common when the value is too complicated or impossible to measure directly. It so happens that the desired value can only be measured indirectly. This may include measuring the size of astronomical bodies.
- What is the cumulative dimension? This is such a measurement in which the desired values are determined by the results of several measurements of quantities with various combinations. The value of the desired value itself is determined by solving a system of equations that are compiled from a series of direct measurements. An example of aggregate measurements: determination of the mass of each weight from a set, that is, it is a calibration based on the known mass of one of the weights, as well as according to the results of direct measurements and comparison of the masses of combinations of weights.
- A joint measurement is one that is performed simultaneously for two or several quantities with different names in order to find a functional relationship between them. An example would be to determine the length of an object as a function of temperature.
Conditional
According to the conditions that determine the accuracy of the result, it is possible to divide the measurements into three classes:
1. Measurement of accuracy, which is maximum. These include measurements of high and reference accuracy.
2. Testing. Their error with some probability should not be higher than some given value.
3. Technical. These are measurements, where the error of the final value is determined by the characteristics of the means used in the measurement process.
Dependence on the methods of expressing results
By the method of expression of the measurement results can be divided into absolute and relative.
- What is the absolute dimension? This is a measurement that is based on direct measurements of quantities or on the application of the values of some physical constants. Examples: determination of amperage, length in meters.
- What is a relative measurement? This is such a measurement in which the desired value is compared with another value that plays the role of unity or is taken as the original. An example of such measurements: finding the relative humidity of the air, which is determined as the ratio of the number of water vapor in a cubic meter of air to the number of vapors saturating a cubic meter of air at a given temperature.
Measurement system
The uniformity of measurements means the consistency of the sizes of all quantities. This is obvious if you pay attention to the fact that the same value can be measured both by direct and indirect methods. Such coherence can be achieved by creating a system of units. The first such system appeared in the late 18th century. She became the well-known metric system. And the first scientifically based system of units was the system proposed by Karl Gauss. Three units were taken as a basis in it: second, millimeter and milligram. It is on the basis of such an absolute system that a modern system of units was built.
What is a unit of measure and what are they
A unit of measure is a specific quantity that is defined and established by agreement. Other quantities of the same kind are compared with it to express their size relative to the indicated value.
Each measured physical quantity must correspond to its own unit of measurement. Thus, separate units are needed to measure speed, length, volume, weight, distance, and so on. Each unit can be determined by choosing a standard. The system of units becomes more convenient if it contains only a few units that are selected as the main ones, and the rest are determined through them. The reference unit of length is the meter. Based on this, the unit of area is considered a square meter, the unit of speed is a meter per second, and the unit of measurement of volume is a meter in a cube.
Error
What is a measurement error? This term refers to the deviation of the measurement results from the actual or true value of the quantity that is being measured. The true value of the quantity is unknown. It is used only in theoretical research.
Sometimes the question "what is the measurement error?" you can hear another definition as an answer - “measurement error”. But it is better not to use it, since it is less successful.
Types of Errors
The systematic error of measurements is a component of the error of the final measurement result, which remains constant or changes naturally with repeated measurements of a physical quantity. The nature of the measurement divides the systematic errors of several types.
- A constant error is an error that retains its significance for a long time. This type is most common.
- A progressive error is one that is continuously increasing or decreasing. This may include errors due to wear of measuring instruments or tips that come into contact with parts.
- Periodic error is the error, the value of which is a periodic function of time or the movement of the pointer of the device used in the measurement.
- The error, which is measured by a complex law , is that which occurs due to the joint action of several systematic errors at once.
Instrumental error is called the component of the measurement error, which is due to the error of the means used.
The error of the measurement method is the component, which is due to the imperfection of the method that is accepted for measurement.
Measurement result
What is a measurement result? This is the value of a physical quantity that is obtained by measuring it.
An uncorrected measurement result is a value that is obtained during a measurement before corrections were introduced into it that take into account systematic errors.
The corrected result is the value of the value obtained during the measurement and refined by introducing the necessary corrections.
The convergence of the measurement results is called the proximity of the results that were repeated using the same means, by the same method and under the same conditions.
What is reproducibility of results? This is the closeness to each other of the results that were obtained in different places, by different means and operators using various methods, but which were brought to the same conditions.
A series of measurement results is a sequence of values of the same value that were obtained as a result of a series of measurements following each other.
Information Measurement
Today, you can measure not only physical quantities. Since the era of computer technology has come, digital information is used everywhere. It is also possible to measure it. What is the measurement of information? This is the definition of the number of data that is expressed in units. The reference unit of information is a bit, which is the amount of information that occurs when events are equally probable. For example, tossing a coin can lead to two equally probable outcomes. The loss of one of the sides contains information with a volume of one bit.
The name of this unit of measurement comes from the abbreviation of the term "binary number". This is a number that can take only two values - one or zero. I use such numbers in all types of computer technology to represent any information. Since a bit is a very small unit of information, it is customary to use larger ones. These are bytes, kilobytes, megabytes, gigabytes, terabytes and so on.
The volume that takes any character entered from the keyboard is one byte. This is 8 bits.
Summary
Thus, all concepts used in the measurement were considered. This is a measurement system, the error and its types, results. It was considered what a unit of measure is, and what these units are. All this must be known to people dealing with science, computing, and also simply to broaden their horizons. Indeed, in the age of information technology, the wisdom that knowledge is power is relevant.