A balancing coil gaugealso operates on principles of magnetic attraction and repulsion. However, a permanent magnet is not used. The base of the indicating arm is pivoted and includes an armature. Two coils are used to create magnetic fields (Figure 21-7)
The two coils are connected so that electricity can flow through either one. When the resisitance of the sending unit is low, the right-hand coil receiver more current than
The left-hand coil, attracting the armature. Thus, the gauge needle moves to the right.