The Vernistat is an A.C. rotating potentiometer consisting of a tapped toroidal transformer, a commutator switch element, a linear 360° tapped resistive element, wipers, and shaft. By means of the commutator switch the voltage taps of the transformer are sequentially applied across the resistive element. In turn, a wiper riding along the resistive element picks off incrementally the voltage applied across the element by means of the commutator switch. If the toroid is tapped in equal increments of voltage, then the output voltage generated through the wiper is linear. If the toroid is tapped in other than equal increments of voltage, then the ouput voltage generated is non-linear. Because of the inherent accuracy and stability of the toroidal transformer and the ability to use high resolution resistance elements made with precious metal alloys, a high resolution, high accuracy, low noise multi-turn potentiometer with stability under temperature extremes can be manufactured.