Workpiece positioning apparatus with plural sensors

摘要: ABSTRACT OF THE DISCLOSURE A sludge lance nozzle for removing from between the tubes of a nuclear steam generator includes positioning apparatus mounted on top nozzle. The are arranged in rows and columns with axes each column lying common plane. is moved perpendicular to planes close one tubes. In embodiment, comprises two transmitter/receivers transmitting signals receiving reflected along parallel planes, being spaced apart by odd multiples one-half tube pitch. received subtracted produce position indicating signal. another embodiment transmitter receiver direction movement nozzle, signal first predetermined direction, responsive only second direction.