High voltage variable resistor with improved central slider contact

Abstract

An arcuate film resistor is defined on an insulating substrate. During use, a high voltage is impressed across end terminals connected to the arcuate film resistor. A central electrode is located on the insulated substrate at a point which is surrounded by the film resistor. The central electrode is formed of a non-film resistor material and has superior adherability to the substrate. A disk-shaped film resistor is deposited at the center of the central electrode and second ring-like film resistor is formed around the outer periphery of the central electrode. A rotatable slider has a first contact positioned over the disk-shaped film resistor and a second contact which slides along the arcuate film resistor. A portion of the voltage from the arcuate film resistor can thus be transferred to the central electrode. The disk-shaped film resistor located on the central electrode improves the contact between the slider at the central electrode. The central electrode adheres better to the substrate and the centrally located film resistor provides better electrical contact. Because the central and outer film resistors are spacially separated, cracks that may develop in the central film resistor do not spread to the outer film resistor.