Linear or angular high-precision position transducers are known, such as the Inductosyn.RTM. transducer; such transducers, however, are only cyclic, that is, the electrical signals supplied by them repeat periodically with the relative displacement between a scale and a slider. With these transducers it is therefore possible to plot the position only within a period or cycle, but it is not possible to identify in which cycle the slider is present relative to the scale.
Normally the displacements of the slider relative to the scale are plotted by means of an electronic system which keeps a count of the number of cycles of the transducer run through during one displacement and adds to this the position plotted within the cycle.
Such a system, therefore, measures the displacements exclusively when the electronic system is operative and completely loses the position if the slider is moved with the electronic system off. As the electronic system is restarted, the position indication is lost and the starting reference must be redetermined with the aid of mechanical means.
Various systems are known for identifying with auxiliary transducers the position of each cycle of a cyclic transducer, but these known systems are very expensive and therefore rarely used.
USPTO Backgrounds
USPTO Backgrounds