Page 822 - Basic Electrical Engineering

Now, let us assume R = 2000 Ω
V

Error in percentage

Thus, we see that the voltmeter resistance must be very high as compared
to the circuit resistance R AB so as to make the measurement error negligible.

Now, let us consider a case of error in measurement due to wrong selection of

instrument range. For example, a voltmeter rated at 0–300 V has its full scale
deflection upto 300 V. Its accuracy is specified in terms of its full scale
deflection. If the same voltmeter is used to measure a low voltage, the

accuracy of measurement will get reduced. That is why, while selecting
measuring instruments, we should select instruments of proper range to avoid

too much error in measurement. This is explained with the help of one
example.