the measurement is difficult to find the true value of the particular parameter.Even if the definition of values of manufactured using proven tools of high quality, there will be a measurement error, which will be numerically equal to the deviation of the true value of those obtained experimentally.At its core, it characterizes the accuracy of the measurements performed.There are several types of this value.
Thus, the measurement error can be static and dynamic.In the first case it is calculated by determining the values of the constants in these conditions, which will be completed when the transients in the elements of equipment and converters.In the second case, the parameter is defined in a changing (dynamic) conditions.Means for measuring this value is calculated by subtracting from the error measuring means, defined in terms of dynamic static error, which corresponds to the value at a particular time.
Also, the measurement error can be systematic and random.In the first case the deviation from the true value remains constant or varies regularly when performing multiple values of repeated measurements of the same parameter.There are many reasons for the appearance of the component.In the most general case, this type of error is a function of:
- measured value;
- variables affecting the value of the measured parameter (here often is the temperature, humidity, pressure and other factors);
- time.
systematic error does not change in magnitude and sign in the case of several parallel experiments.It depends on several factors:
1. The inaccuracy of instruments, which manifests itself in a deviation from the parameters of measuring nominal properties.In this way it formed the instrumental measurement error, which is calculated for each individual instrument.
2. Inadequate or wrong choice of the method of measurements: systematic error.
3. The human factor, that is, subjective error.
4. Influence of some factors from the external environment.
random component is the result of the combined action of a number of reasons, which appear randomly at each dimension, for example, as a result of the constant voltage ripple.Therefore, the manifestation of this component is difficult to predict, and therefore excluded.To minimize the effect of random errors on the final result of a measurement is performed several approaches, the results of which is determined by the average value of the parameter.
Accuracy depends on how you define the desired value.Accuracy of direct measurements are not determined as indirect.In the first case, the value of a quantity is itself in the process of measurement, that is, directly followed by the well-known formula is calculated deviation.In the second case empirically determined by a parameter, knowing that we can calculate the required value.Only then can be calculated from indirect measurements of the error.
It should also be noted that it can be presented in different forms.In particular allocate absolute, relative and cast.In the first case is the difference between the nominal and the actual measured value.In the second - the ratio of the absolute error and the true value.Reduced error of measurement is determined by dividing the value of the absolute value of which is conventionally taken as a constant for a given measurement interval.What form of presentation you choose will depend on the particular experiment.
