AVO-METER:

An avo-meter is an instrument to measure the current, voltage and resistance. The letters A. V. O, in fact stand for ampere, volt and ohm respectively. It can measure direct as well as alternating current and voltage.
An avo-meter consists of a galvanometer provided with a series of combinations of resistances, all enclosed in a box. It has different scales graduated in such a manner that all the three quantities can be measured. It has its own battery for its function and for operating the electrical circuits. The quantity to be measured and its range can be selected by a selector switch, which connects the particular electrical circuit to the galvanometer.

USES:
CURRENT MEASURING.
VOLTAGE MEASURING.
RESISTANCE MEASURING.