A device for the sensing and the measuring of the axial tension stresses occurring within the bolt of a threaded fastening system under installation comprising a metallic, electrically conductive flat washer-like first member, and a metallic, electrically insulated flat washer-like second member; wherein...http://www.google.es/patents/US4106370?utm_source=gb-gplus-sharePatente US4106370 - Electric infinite-range load-sensing transducer
