| 摘要 |
<p>A positional encoder is provided with a plurality of Hall-effect linear sensors aligned along a generating line of a cylinder transparent to a magnetic field; sliding inside the cylinder is a piston the head of which is permanently fixed to a magnetic disk. The piston's shank is connected to a gauge for off line measurement of the absolute position of the magnet and therefore the head of the piston. A multiplexer cyclically acquires samples of responses from all the sensors and sends them on to a processor. The samples are written in a calibrating memory together with the value measured at that position. The operation is repeated for all the positions established by the desired resolution, and the gauge is then disconnected. When operation is in line, the samples passed on by the multiplexer are systematically compared with the calibrated values in each positional map in order to calculate a cumulative distance for each one. The map chosen is the one that provides the minimum cumulative distance and this one gives the estimated positional value. To obtain a better resolution, the single responses between adjacent points can be interpolated.</p> |
