A terminal assembly includes a wire including a core made of metal and covered with a coating, a terminal including a wire connecting portion connected to an end portion of the wire, a sealing resin sealing the wire connecting portion, and a housing including a through hole with a front opening and a rear opening. The device also includes a coating film made of a dielectric having a function of storing electric charge and formed on the substrate in such a manner as to cover an upper surface and side surfaces of the gate electrode. Said displacement measuring system further comprises a second x-sensor.