Question

A voltmeter reads 128.8V when connected across the component if the true value if the voltage is 112.6V calculate
(i) static error
(ii) static correction for the voltmeter
(iii) Relative error.

Answer 1

(i) The static error is just a difference between a true value (which is technically impossible to know for sure, but possible to measure) and the measured value:

$$\Delta_V=V_M-V_T=128.8-112.6=16.2\text{ V}.$$

(ii) Since the readings are 16.2 V higher than the true value, the static correction should be 16.2 V (the correction screw on the voltmeter should be set so that at 112.6 V of true voltage the readings would be as close as possible to 112.6 V).

(iii) The relative error is the static error over the true value:

$$\epsilon_V=\frac{\Delta_V}{V_T}\cdot100\%=\frac{16.2}{112.6}\cdot100\%=14.4\%.$$