Features of Piezobolt Force Transducers

Since every technical force measurement is basically based on a strain measurement, there is often a conflict of goals when choosing the measurement location: On the one hand, the highest signal yield (greatest forces) and a clear force line (single-axis load case) are desired, on the other hand, there is the requirement to easily integrate sensors and to affect the stiffness of the system as little as possible. Figure 2 illustrates this with typical possible solutions in which the pressing or lifting force between two plates is to be detected with the help of standard force transducers. a) PiezoBolt, b) Force Load Ring, c) Force Load Cell, d) Force Load Ring in the Main Force Flow.

A closer look at the force transducer integration proposals shows that PiezoBolts obviously involve the least modification effort. Even more important in practical application, however, is that solutions b), c) and d) often significantly reduce the stiffness of the system to be measured, in addition to the sensitivity to torque application explained at the beginning. In addition, for load cells and rings, the prices typically increase quadratically with the diameter due to the necessary load capacity, whereas the investment for PiezoBolts is essentially independent of the load to be detected.

These advantages can only be exploited with PiezoBolts because the sensor-active material used enables a large signal yield and the special sensor design over the working area enables excellent linearity properties. Strain gauge or ultrasound-based screw sensors cannot achieve this resolution for force signals due to their principle.

Of course, PiezoBolt force transducers can also play to their strengths when integrated into assemblies. Figure 4 shows typical installation situations that are regularly used in this way or in a varied form. Exemplary force measurement locations in the context of assemblies are: a) bearing cover or flange screw connection, b) bearing block or flange with transverse loading, c) modification of thrust pieces, d) force detection in backings or during assemblies.

In the case of measuring points a), b) and d), basic knowledge of screw technology for the evaluation of the force application case can be used for the evaluation of the expected measurement result. Application case c) can be evaluated by estimating the strain field due to transverse contraction.