Because of particularity of structure and material, the piston must be measured by the non - contact method. but, at present there isn ' t mature technique.
由于活塞结构和材料的特殊性，对于它的检测只能采用非接触测量的方法，而目前尚没有成熟的技术。
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Also offered is a non-contact, piston detection sensor for use with steel hydraulic cylinders.