Measuring Instruments

A measuring instrument is a device for measuring a physical quantity like the voltage, current etc. Voltmeter and Ammeter are the measuring instruments. A voltmeter is an instrument used for measuring the electrical potential difference between two points in an electric circuit. A voltmeter is connected in parallel with a device to measure its voltage, while an ammeter is connected in series with a device to measure its current.

Ammeters work to measure electrical current by measuring the current through a set of coils with very low resistance and inductive reactance.