Design of a three – components capacitive force transducer

A three-component capacitive force/moment transducer was designed and developed. The moments Mx , My , and the normal force Fz are sensed. The capacitor electrode conformation and disposition was designed to allow a greatly simplified circuit topology and limit the influence of stray capacitances. The capacitive displacement sensor exhibits an intrinsic sensitivity of about 20 ~V/ V!/rad for the tangential components and 6~V/V!/mm for the normal one. With proper amplifying circuitry a minimum detectable signal of 0.331024 rad/Hz21/2 and 0.1 mm/Hz21/2 was achieved. Different elastic elements were tested in order to vary the nominal load of the force transducer and to achieve different sensitivities. These values are roughly 102 times the values of traditional strain gages units. The proposed device is mainly intended for the mechanical characterization of nonstandard specimens, and is presented for the purpose of performing microtraction tests on biological samples while monitoring off axis components.