GB1210580A - Improvements in or relating to layer resistance elements for voltage dividers - Google Patents

Abstract

1,210,580. Variable resistors. WALTER PREH [trading as PREH ELEKTROFEINMECHANISCHE WERKE JACOB PREH NACHFOLGER]. 26 Nov., 1968 [1 Dec., 1967; 20 Feb., 1968; 10 April, 1968], No. 56134/68. Heading H1S. A resistance element for a variable voltage divider comprises resistive material on a substrate, the element being divided into sections by transverse conductive strips C, D, G, each section including a main resistance part B and a shunt resistance part N, the main resistance parts presenting a wiper path S and the shunt resistance parts being adjusted so that each section resistance is matched to the values given by a voltage characteristic curve. Tolerances of less than 2 per cent can be achieved, whereby the voltage divider is suitable for tuning HF circuits by varying the blocking voltage of variale capacitance diodes. Conductive strips C, D, G are as thin as possible to avoid step changes in voltage, and may be interrupted in the region of the wiper path S. As shown, for a voltage divider having a non-lever characteristic curve further parallel resistances P I , P II and P III may be included, the latter being integral with shunt resistance N III . Adjustment of the shunt resistances may be achieved by removal of resistive material by scoring along the dashed line, preferably by a motor driven tool controlled by a resistance measurement device so that it stops when the correct trimming has taken place. Alternatively, the shunt resistances may be short circuited by a conductive strip along one edge, and the resistances increased by removal of this strip (Fig. 2, not shown). The resistance element may be circular (Fig. 4, not shown) or a multiple divider may have common conductive cross-pieces and the thus parallel-connected sections have common trimmable shunt resistances (Fig. 6, not shown). The circular element is shown as having a further track and shunt section at the initial terminal to give a base-point resistance matchable to an exact fraction of the total voltage. In a modification (Figs. 8, 9, not shown) the track resistance of every second section has its own wiper for independent variation so that the divider has a number of continuously adjustable stepped voltages.