Abstract: When a load current on a motor was to be monitored, all the digital values of the load current at the model operation were conveniently memorized in a memory to be compared with the load current value of the actual operation. The capacity of the memory therefore became enormous, presenting a problem. This invention enables to memorize a load current of a motor at the model operation in terms of the dimensional difference from a reference value and of duration of time. Thanks to such an arrangement, the volume of stored data can be reduced to minimize the capacity of the memory, thereby facilitating the comparison process of data at the time of actual operation.

Abstract: In machine tools it is necessary to monitor the track of a cutter tip on a tool post. A predetermined tolerance scope is given to sampling positions during the model cutting, and only the data of the points and distance defining the tolerance scope is stored. During the actual cutting, a determination is made as to whether or not a sampling position is within the tolerance scope and the track is thereby securely monitored.