A.C. capacitance measuring bridge

An alternating current capacitance measuring bridge for measuring the capacitance of capacitors having one terminal connected to an ground comprising an alternating voltage source, a differential transformer having a primary winding connected to said alternating voltage source and two secondary windings having a common terminal, screened coaxial connections for connecting said capacitors to said secondary windings, a detector inserted in said common terminal of said secondary windings via an amplification stage, a first metal screen box connected to said common terminal of said secondary windings inside of which said alternating voltage source and said primary and secondary windings are placed, whose interior is connected directly to first conductors of the screens of said screened coaxial connections, which surround coaxially the internal conductors of said screened coaxial connections, means for direct current supplying said alternating voltage source via internal direct current supply terminals comprising a first winding connecting to said common terminal of said secondary windings and said external earth, a second and a third windings connecting to said internal direct current supply terminals and external direct current supply terminals, said first, second and third windings having a high impedance at the operational frequency of said alternating voltage source, two first capacitors of high impedance inserted between said internal direct current supply terminals and said first metal screen box, and two second capacitors of high impedance inserted between said external direct current terminals and said external earth.