This paper describes a unique sensing method to apply an InSb Hall element that enables simultaneous sensing device to detect thickness of insulating film on an iron plate and temperature. We made a trial thickness-temperature sensor consists of an InSb Hall element and a small permanent magnet. Here, the film thickness is detected by the variation in distance between the Hall element with the magnet and the iron plate. The temperature characteristic of an InSb Hall element depends on the drive circuit to generate the Hall voltage. Therefore, the Hall element is driven using a constant voltage source and a constant current source by time-division to obtain two kinds of Hall output voltages. Two output Hall voltages driven by two kinds of bias circuits are measured in the film thickness range from 0 to 500 μm, and for a temperature range of -10 to 70 °C. The inverse response surfaces that are used to identify the thickness of insulating film and temperature are formulated using experimental results. The results obtained show that it is possible to detect film thickness and temperature by obtaining two kinds of Hall voltages.
In this paper, we reports on a tactile sensor with Hall effect elements, which are generally used as magnetic sensors, for multimodal sensing devices to detect the contact force and the temperature. This tactile sensor consists of Hall elements and a magnet that are embedded in an elastic silicone rubber as the artificial skin. Here, the normal contact force is detected by distance change between a Hall element and a magnet, and the temperature is also detected using the temperature dependence of the Hall element. The temperature dependence of Hall elements depends on the Hall material and the drive circuit to generate the Hall voltage. In this study, two Indium antimonide (InSb) Hall elements and two drive circuits, that is, a constant voltage drive and a constant current drive were used to demonstrate the tactile sensor. Two output Hall voltages were measured in the normal contact force range from 0 to 50N, the temperature range from -10 to 50°C. The inverse response surface to identify the normal contact force and the temperature was formulated using the experimental results. It was possible to detect the contact force and the temperature by obtaining two kinds of Hall voltages.