Liquid crystal applied voltmeter

Claim 1

A decibel meter comprising: (a) a pair of polaroidal plates disposed in parallel opposed position, said polaroidal plates being arranged so that their polarizing directions intersect at a right angle, (b) a pair of light-transmitting electrodes disposed in spaced parallel relationship between said polaroidal plates, one of said electrodes comprising an electrical resistance film, the other of said electrodes comprising a conductor film, one end of said electric resistance film being electrically connected to one end of said conductor film, (c) a nematic liquid crystal, adapted to produce a DAP effect, filling a space defined between said electrodes (d) a scale indicating means on one of said polaroidal plates on a surface thereof which is remote from said liquid crystal, said scale means having graduations at substantially equal intervals (e) a constant voltage power supply electrically connected to said one electrode comprising said electrical resistance film for applying a constant voltage to thereto such that a voltage gradient occurs from one end to the other of said electrode, the resistance value per unit length of said resistance film from one end to the other of said film varying as the inverse of an exponential function, said constant voltage and a voltage to be measured being applied in series across the two ends of said electrical resistance film.