An ac two-core transducer assembly using a-Fe81B13.5Si3.5C2 and a-Fe40Ni40B20 ribbon to detect small displacement and current is proposed. The amorphous material is kept at 'zero-flux state' by applying equal and opposite ac magnetic fields. When this state is disturbed by an external magnetic field, an ac signal is produced which is proportional to the external field produced by a bar magnet or current carrying coil. The results for the sensitivity and linearity with displacement (linear and angular) of a magnet and with current are presented for two configurations of transducer. © 1987.