USED for deflection, the controlling torque acts opposite to the deflecting torque. So before coming to rest the pointer ALWAYS oscillates due to inertia, so to bring the pointer rest within a SHORT time by reducing oscillations, we use damping torque without effecting controlling torque (or) inertia.The following mechanism can be used for producing damping torque.1. Air friction damping2. Fluid friction damping3. Eddy current dampingThe damping device should be such that it PRODUCES a damping torque only while the moving system is in motion. To be effective the damping torque should be proportional to the velocity of the moving current but independent of operating current.In PMMC instruments, the damping torque is provided by eddy current damping since the presence of a permanent magnet.