How does a moving coil ammeter work?

Question

i,ve lookd through the internet n foun nothing. i hope u can xplain how it works .how radial field is applied .the function of hair spring,current flow and all.i really/33 need help!!!!!please!!

thanx in advance~~

Answer 1

Its called a D'arsonval meter movement.

To oversimplify its operation, it works like a motor except the shaft isn't allowed to spin round and round. Rather the force that would spin the shaft of the motor is counteracted by a coil spring.   The movement of the bobbin is limited to about 90  to 120 degrees, less then 1/2 a revolution.

A bobbin or coil of wire is placed in a magnetic field.  Without any current flowing through it the spring twists the bobbin to the zero position.   As current is applies to the bobbin a magnetic field is generated in the bobbin.  The interaction of the two magnetic Fields (opposite poles attract,like poles repel) creates a force that causes the bobbin to move.   As the bobbin moves the spring winds tighter and eventually balances the the force trying to move the bobbin.

A needle is attached to the bobbin and the movement of the needle is referenced to a printed scale that is calibrated in Volts or amps for example.