EXTERNAL FORCE MEASURING APPARATUS AND PARTS MOUNTING APPARATUS USING THE SAME

摘要

PURPOSE:To obtain an external force-measuring apparatus, to which an electrical charge amplifier is connected at output terminals of a piezoelectric element, capable of suppressing the reduction of an output voltage to the best of its ability and obtaining a value accurately measured even when the measurement is repeated so often. CONSTITUTION:In an external force-measuring apparatus having a piezoelectric element 61 which generates an electric charge by an external pressure and an electric charge amplifier 7 which charges a differential charge generated by the piezoelectric element to output a voltage signal, a switch 8 capable of being controlled in on/off states is connected in parallel to a feedback loop forming the electric charge amplifier 7. The switch 8 is controlled in on/off states by a comparator 81 or the like which compares the output voltage with a reference value so that the switch is closed while the external force is not applied.