Precision AC current measuring device for railway signals - has magnetic circuit surrounding conductor and presenting coil which detects magnetic flux generated by current through conductor

摘要

The device includes a magnetic circuit (14), which surrounds a central hole (1) and a coil (6) wound around the magnetic circuit. The magnetic flux generated by a current (I1) through a conductor inserted in the central hole is detected by the coil which is connected to an amplifier (7). A phase shifted current (I1) is generated in a second coil (5) also surrounding the magnetic circuit. The second coil is connected to a current measuring circuit (12) which includes a calibration coil (10) and a current generator (11) which produces a current of well known amplitude and frequency.