Conventional transducers measure the strain in a compliant member and based on their stiffness, determine the torque resp. normal force (Fig. 1a). This method has several inherent disadvantages. Since the compliant member is strained, the strain has to be accounted for in determining actual sample strain. In dynamic the inertia of the moving mass of the transducer, affects the measured results at high frequences. Further, viscoelastic materials which develop normal forces, drive the cone and plate apart. This effect generates secondary flow fields and the result is an inaccurate transient normal force measurement. To overcome these problems of conventional transducer, all developments have been made towards stiffer transducers. The stiffness however is directly related to the resolution of the strain measurement of the compliant member i.e. the torque resp. force measurement. This implies that the stress resolution decreases with increasing stiffness.
