Meter works

According to ammeter is energized conductor in a magnetic field by the magnetic force of the steel.
Meter inside a permanent magnet, a magnetic field is generated between the electrode in a magnetic field with a coil spring at each end coil springs, each connected to

a Electric energy meter ,  and the coil spring consists of a shaft coupling, the shaft is relatively on ammeter ago

Side, there is a pointer.
When a current is passed, the current along the spring, shaft through a magnetic field, the current cut magnetic induction lines, and therefore the magnetic force, so

that the coil deflected drive shaft, pointer deflection.
The size of the magnetic field strength increases with increasing current, so that the degree of deflection via the pointer to observe the current size.
Called magneto-electric meter , is what we usually kind used in laboratories.