What are the different methods to provide controlling torque in an analog instrument ?

The controlling torque in an analog instrument may be provided by one of the following methods....
   ¥ by one or more springs -spring control.
   ¥ by weight of moving parts - gravity control.

In spring control system one or more springs attached to the deflecting system. The springs should be non magnetic . With the deflection of moving part the springs will twisted in opposite direction . This twist in springs provide controlling torque .
      In the case of gravity control a small adjustable weight is attached to the moving system which provides sufficient controlling torque.