D.C. voltage ratio measuring circuit

A measurement circuit for measuring the ratio of the magnitudes of two D-C voltages of fixed polarity and translating said ratio into a representing voltage, comprising three voltage dividers connected to a common ground point and each consisting of a fixed resistor and a variable resistor having a resistance value sensitive to the voltage applied thereto, wherein a first and a second of said dividers are respectively fed with direct current by said D-C voltages of fixed polarity, while the third of said dividers is fed with a direct current by means of a further D-C voltage derived from at least one of said D-C voltages of fixed polarity and with an alternating current voltage delivered by a source of constant amplitude, wherein the alternating current voltage appearing at the mid-point of said third divider feeds both said first and second dividers, wherein the series-connection order with respect to ground of said fixed and variable resistors is the same in said first and second dividers and is reversed in said third divider, and wherein the difference between the alternating current voltages received at the mid-points of said first and second dividers is converted into said representing voltage by amplification, rectification and filtering in an output circuit.