Patent ID: 7388363

Claim:
A detector circuit to be used for measuring current by means of substantially identically wound ring core transformers, in which magnetomotive forces are induced by a main current (I 5 ), said magnetomotive forces being counteracted by magnetomotive forces induced by a compensating current (i 4 ), and where two of the ring core transformers ( 2 , 3 ) are magnetized in antiphase by means of a modulation current, said detector circuit optionally also including a synchronous rectifier for generating an adjusting signal for the compensating current, and where means are provided for compensating for possible differences between the two ring core transformers ( 2 , 3 ), characterised by the means for compensating for possible differences between the ring core transformers ( 2 , 3 ) being formed by a common winding (L 6 ) surrounding the two ring cores ( 2 , 3 ), said common winding (L 6 ) detecting a possible error signal used in a negative feedback loop which automatically seeks to establish an equilibrium.