Design, manufacture, and calibration of Foucault current sensors

The development and production of Foucalt current sensors for low frequencies (between 1 and 3 kHz) is described. These sensors are to be used in fault detection of sheet assemblies between 1 and 5 mm in thickness. Nine sensors are produced. Three coils without a central core demonstrate that the ferrite core improves the magnetic coupling between the sensor and the panel studied by approximately 50 percent, and the detection of a fault by about 14 dB. The electric characteristics measured by means of an impedance meter seem to provide good indication of the quality of the sensors during both production and operating phases.