Abstract:
Relative movement between two members is sensed by a device yielding a signal during successive increments of movement. A first circuit means applies one pulse to a reversible counter for each incremental movement and a second circuit controls the direction of counting to accord with that of movement.
Abstract:
An apparatus for providing electrical signals representative of relative movement between two members includes a source of radiant energy conveniently light. A movement sensor fixed to one of the movable members comprises at least one detector responsive to energy from the source. A graduated track fixed to the other movable member is composed of a regular alternating series of marks and spaces capable of varying differently the energy from the source which is received by the detector by way of the track. Thus each detector provides a periodic undulating signal as the two members move relatively to one another. The or each signal is transformed by a reshaping device in which it is compared with a reference signal derived from at least one other detector exposed to energy from the source to derive a rectangular signal varying between one and the other of two logic levels. The reference signal may be derived by combining signals from two or more detectors exposed to energy from the source after modification by the track.
Abstract:
Counting errors are automatically detected in a displacement measuring system using encoding and counting by sensing a value CL and substracting it from a value CE registered by a counter. The difference of the values is memorized at the beginning of measurement and is then continuously compared with the memorized difference. Non-coincidence between the instantaneous difference and the memorized difference actuates an alarm.