Some applications in industry and consumer goods require the acquisition of measurement data to comply with legal guidelines. These legal guidelines require proof of compliance with certain assembly steps and requirements to ensure safety standards. For example, proof must be provided of the torque used to tighten nuts or bolts during the installation of wind turbines or roller coasters. In other applications, documentation of certain assembly steps may result, among other things, in fewer verifications. For example, documenting how tightly the wheel nuts have been tightened when changing them may mean that it is not necessary to tighten them again until a certain number of kilometres have been travelled. This means that the collection of measurement data during assembly steps can, on the one hand, increase the safety of the people working with the machines and, on the other hand, reduce the effort required for safety-relevant tests. Measurement data acquisition requires sensor technology that converts physical quantity into electrical quantity and electronics that record and evaluate measurement data so that it can be documented for verification purposes. The information from the electric motors is normally used for the acquisition of torque information. Their voltage and current are a measure of the energy consumed. The input power with additional information about the geometry of the tool can be used to calculate the output torque. This calculation depends on several factors. For example, due to ageing of the bearings of a torque wrench, its efficiency may change. As a result, the input power, which is calculated using current and voltage, does not correspondto the effective power and is therefore defective.
Temperature influences on the electric motor can also cause the intrinsic ohmic resistance of copper coatings to change. This causes a change in the current consumption and therefore in the energy consumption of the electric motor. As a result of these changing conditions, the electric motor operates at a different operating point. This operating point change requires an adjustment of the torque calculation. In order to take into account these error influences, which accumulate during operation, a certain safety margin must be taken into account. The tools used must be designed in such a way as to achieve this safety margin, i.e. the required torque plus a certain error. This means that the tools used must be large in size in order to be suitable for the application and, on the other hand, they must be checked at regular intervals to ensure that they still meet the necessary requirements. A much simpler and safer system can be achieved if the torque is recorded directly at the measurement point where the required torque must be achieved. The torque sensors currently available on the market are not commercially interesting for these applications, as they are expensive and it is difficult to have the necessary installation space, so it is not always possible to integrate them into the application. Magnetic Sense is currently working on a solution to measure these torques directly using a magnetic inductive torque or force sensor. The technology is based on the detection of an interaction between the coupled magnetic fields and the magnetic properties of waves that change due to the application of force. The use of magnetic field sensors has become very popular in recent years. The sensors can be constructed in such a way that they are extremely robust against possible interference and can be used over a long period of time.