Abstract: A rod member provided with magnetic and non-magnetic portion arranged alternatingly is provided and a plurality of detecting heads for detecting magnetic resistance are disposed along the longitudinal direction of the rod member with predetermined distances, respectively. The pitches of the respective pairs of the magnetic and non-magnetic portions are arranged with pitches different with each other by the predetermined distances. Output signals transmitted from the detecting heads in accordance with the relative movement between the rod member and the detecting heads are detected by phase detectors, and on the basis of the detected signals, the predetermined operation is carried out in an operation processing unit thereby to obtain the absolute positional relation between the rod member and the detecting heads in, for example, of a positioning system such as in a die casting machine.

Abstract: A digital mode phase modulation type position detector utilizing a resolver as the phase modulating element is disclosed in which the phase of the modulated signal is determined by comparing it with that of the follower signal, the phase of which is adjusted to that of the modulated signal. The phase difference between the modulated and the follower signal is detected at the ends of the half-periods thereof to effect the adjustment. To make the adjustment more precise, an adjustment circuit may further be provided which generates evenly spaced pulses in the present half-period of the follower signal at a frequency corresponding to the rotational speed of the resolver during the preceding half-period of the modulated signal. These pulses are used to adjust the phase of the follower signal more closely to that of the modulated signal.