A Galvanometer is used for detecting and measuring small electric currents and can be modified to serve as an ammeter or voltmeter with the addition of specific resistances.
The instrument used for detecting and measuring small electric currents is a Galvanometer. A galvanometer operates on the principle that a current-carrying coil within a magnetic field experiences a torque, which causes a pointer to move across a scale, thus giving an analog reading of the current.
To increase its usability, when a galvanometer is combined with a small resistance in parallel, known as a shunt resistance, it can function as an ammeter and measure larger currents. Conversely, pairing a galvanometer with a larger resistance in series enables it to operate as a voltmeter, appropriate for measuring potentials across a circuit.