# Answer to Question #65002 in Electric Circuits for megha

Question #65002

what is meant by range of an ammeter? also of voltmeter and galvanometer?

Expert's answer

Range of ammeter(voltmeter) is maximum current(voltage) that this ammeter(voltmeter) can measure. The range corresponds to full-scale voltage or current. The advantage of using ranges is greater accuracy.

For example, suppose you measure 0.8V on a 1V range and on a 100V range.

For an analog meter, you estimate the reading by eye against a scale, while for a digital meter there is an analog to digital converter with a certain number of bits resolution.

Suppose 10 bits corresponds to full scale - 1 bit is about 0.1V on a 100V scale and 0.001V on a 1V scale. So on the 1V scale you have 0.8V +/- 0.001V or about 0.1% accuracy, and on the 100V scale you have 0.8V +/- 0.1V or about 10% accuracy.

A similar problem exists on the analog meter - you just can't read it that well.

For example, suppose you measure 0.8V on a 1V range and on a 100V range.

For an analog meter, you estimate the reading by eye against a scale, while for a digital meter there is an analog to digital converter with a certain number of bits resolution.

Suppose 10 bits corresponds to full scale - 1 bit is about 0.1V on a 100V scale and 0.001V on a 1V scale. So on the 1V scale you have 0.8V +/- 0.001V or about 0.1% accuracy, and on the 100V scale you have 0.8V +/- 0.1V or about 10% accuracy.

A similar problem exists on the analog meter - you just can't read it that well.

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