| 摘要 |
Absolute determination of position/displacement e.g. of a piston 13 in a hydraulic ram is by means of a loading armature 19 carried by the ram piston and shiftable along a stationary elongate stator 17 having a regularly multi-tapped winding forming a series of windings each of axial length equal to half the axial length of the armature. "Coarse" determination of the armature position is effected by scanning the series of windings and for each winding measuring the impedance. Detection of low impedance shows the presence of the armature. Thereafter, a group of the windings in the vicinity of the armature is examined by means of a bridge circuit and analogue values of impedance used to determine accurately the "fine" position of the armature. A feature of the apparatus is automatic step-switching between adjacent groups of windings so that analogue values are maintained within limits corresponding to linear variations. The armature 19 is a solid metal insert e.g. of aluminium and the starter is anchored by a pressure-tight gland 18. <IMAGE> |
