DETECTOR FOR DIFFERENT MATERIAL

PURPOSE:To quickly discriminate a material to be tested by connecting primary and secondary coils to a standard material and a material to be tested, connecting the primary coils to an AC source and comparing the output voltages of the secondary coils. CONSTITUTION:A standard material 1 has a primary coil 3 and a secondary coil magnetically coupled with the primary one. A material 2 to be tested has also a primary coil 3 and a secondary coil 6. These primary coils 3, 5 are connected in series and excited by an electric power source 7 and the secondary coils 4, 6 constitute a bridge circuit 10 together with impedance elements 8, 9. When the standard material 1 is coincident with the material 2 to be tested, the bridge circuit 10 keeps its equilibrium, but when the latter material 2 is different from the former 1, the bridge circuit 10 is unbalanced. When a magnetic material is to be tested, AC voltage including a DC component is used for exitation to make the material magnetically unsaturated status.