In mass production the condition falls, often detect appropriative automatically device installation is on the machine tool, need not stop machine, can detect automatically in machining a process the change of work measure, can issue corresponding signal according to measuring gotten result, the treatment process that controls a machine tool (if alternate compensation of cutting dosage, cutting tool, stop feed, retreat knife and stop machine) . Issue plan institute to show for example measure the principle that reachs feedback control equipment automatically to pursue for external diameter of the workpiece on grinder. While grinder is machined, measure a head automatically to undertake metrical to workpiece, measures workpiece size change estimates classics signal changeover and amplifier, changeover becomes corresponding electric signal, after classics enlarge, return a machine tool to control a system, through actuator control machines a process. External diameter of the workpiece on grinder measures a principle automatically to pursue CNC MillingCNC Machining