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precision class greater than 4 are used as demos. The accuracy class of
the instrument is indicated on its scale.

Example of calculation of developments measured electricity

for classes of accuracy of equipment.
In many cases, the values of the desired electrical value are
obtained by the results of one measurement. Therefore, a special role

is played by way of estimating the errors of measurements. Let's
consider individual cases.

Direct measurement of electric size.
For example, an ammeter, whose scale is calculated at 1A, we
will conduct a one-time measurement of current strength of 0.8A. The
accuracy class of the device is 1. Given that the accuracy class of the

instrument is its error, expressed in percentages according to formula
(1.3), we will have

I 
0,01 ,
1A

where the absolute error of measuring the current strength of this
instrument is I = 0.011A = 0,01А and therefore the value of the

current strength obtained should be considered equal to

І = (0,8 0,01) А

Indirect measurement of electric size.
Indirect measurements of some physical value are such
measurements when the desired value is obtained as a result of

calculations on the results of measurements of a number of other
quantities. For example, according to the Ohm law for a circle, the
resistance of a conductor can be calculated by the formula

U
R  (1.4)
I

But for this purpose, it is necessary to conduct direct
measurements of the current and voltage. Let the current is 0.8A, and

the voltage is 160V. Then, by the formula (1.4), we find the resistance,
which is equal to

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