| 摘要 |
A longitudinal magnetic circuit comprises a bar (23) with three equally spaced orthogonal radial elements (26,27) at either end. At one end (27) Hall effect magnetic field strength sensors (3) are located in airgaps (2) in the radial elements. The magnetic circuit is energised by an alternating current winding (4) and the output of each of the magnetic field strength sensors (3) is fed to processing circuits (9).The processing circuits (9) use the alternating signal from the winding (4) to invert even half cycles of sensor output, integrate the peaks and detect directional increases above a predetermined threshold.
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