| 摘要 |
A permanent magnet (10) moves with a moving object or float and on the same side of a non-magnetic wall (12). An indicator element (18) mounted on the other side of the wall forms, with the magnet, a magnetic circuit passing through the wall. The indicator element is guided (16) so as to move parallel to the path of the object. A magnetic lubricant is provided at the boundary between the indicator element and guide. The lubricant consists of a fluid carrier contg. a colloidal suspension of solid magnetic particles. The indicator element may be a second permanent magnet or a non-magnetised e.g. soft iron, object moving in a guide tube. Alternatively, it may be a coloured magnetic fluid.
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