When measuring, it is difficult to find the true value of a particular parameter. Even if the determination of the value of the value is carried out using proven high-quality tools, there will be a measurement error, which will become numerically equal to the deviation of the true value from that obtained experimentally. At its core, it characterizes the accuracy of measurements. There are several types of this value.
So, the measurement error can be static and dynamic. In the first case, it is calculated when determining the values of constant values in such conditions under which transients in the elements of devices and converters will be completed. In the second case, the parameter is determined in changing (dynamic) conditions. For measuring instruments, this value is calculated by subtracting from the error of the measuring instrument, determined in the dynamic conditions of the static error, which corresponds to the value of the value at a particular point in time.
Also, the measurement error can be systematic and random. In the first case, the deviation from the true value remains constant or naturally changes during several repeated measurements of the value of the same parameter. There are a large number of reasons for the appearance of this component. In the most general case, this type of error is a function of:
- measured value;
- values that influence the value of the measured parameter (this most often includes temperature, humidity, voltage and other factors);
- time.
The systematic error does not change modulo and sign in the case of several parallel experiments. It depends on a number of factors:
1. Inaccuracy of instruments, which is manifested in the deviation of the parameters of the measuring instruments from the nominal properties. Due to this, an instrumental measurement error is generated, which is calculated for each specific tool.
2. Imperfection or inaccuracy of the choice of the method of measurement: methodological error.
3. The human factor, that is, subjective error.
4. The influence of certain factors from the external environment.
The random component arises as a result of the combined action of a number of reasons that appear randomly for each specific measurement, for example, as a result of ripple of the constant supply voltage. Therefore, the manifestation of this component is difficult to predict, and therefore excluded. In order to minimize the effect of random error on the final measurement result, several approaches are performed, the results of which determine the average value of the desired parameter.
The error depends on the method of determining the desired value. The error of direct measurements is not determined as indirect. In the first case, the value of some quantity is directly in the measurement process, that is, directly, and then the deviation is calculated using the well-known formula. In the second case, a parameter is determined empirically, knowing which, one can calculate the desired value. Only then can the error of indirect measurements be calculated.
It is also worth noting that it can be presented in various forms. In particular, absolute, relative and reduced are distinguished. In the first case, the difference between the nominal and actual values of the measured value is found. In the second - the ratio of absolute error and true value. The given measurement error is determined by dividing the absolute by the value of the value, which is conventionally accepted as constant for a particular measurement interval. Which form of presentation you choose will depend on the particular experiment.