Most magnetic sensor systems consist of a magnetic-field sensor that measures the magnetic field in one or more directions and a magnetic element that creates the magnetic field. Different kinds of stimuli change the distance or the orientation of the magnetic element with respect to the magnetic-field sensor, and even the magnetic properties of the material in the magnetic element can change with specific stimuli, which can be detected by the sensor. Thus, a magnetic sensor system can detect all kinds of parameters such as distance, orientation, forces, motion, leakage or even different kinds of molecules in a liquid.
In other cases, a magnetic-field sensor can detect the magnetic orientation in the magnetic element (which can be used to store data as zeros and ones) positioned on a hard disk in a computer or in other types of information-carrier media. The magnetic field sensor can either be a sensitive and low noise ordinary magnetoresistive sensor or a giant magnetoresistive (GMR) sensor, a Hall sensor (which is used in a wider field range) or just a coil with copper windings (used at higher frequencies since its sensitivity increases linearly with the frequency).
Motion and position detection
The classic magnetic-sensor system for position and orientation detection is constructed as follows. Around a permanent magnet is a magnetic field. The strength and direction of this magnetic field depends on the distance and direction to the permanent magnet (and also on the dimension and geometry of the magnet) in a complex way. However, for small changes in direction and orientation, the strength is more or less linear to the changes in both distance or changes in orientation. Together with a sufficiently sensitive magnetic-field sensor that can measure the magnetic field strength in one or more orthogonal directions, it can be used to measure changes in position down to a few micrometers up to several millimeters and angle changes down to a few milliradians up to a full rotation of an object. This kind of sensor system can be used for many application areas where changes in distance or orientation between two or more objects occur. The complete sensor system is very cost effective in many applications. It can also be used in harsh environments (for instance in high temperature conditions).
Detection of vehicles
We have designed a sensor system using commercially available magnetic sensorsto detect traffic. We found that it is possible to measure the velocity of vehicles and the direction of vehicle movement and even to distinguish different type of vehicles. The magnetic-sensor system enables passive remote detection, with high accuracy and at low cost.
Field scanning using magnetic sensors
We have experience in our magnetic lab with measuring the field pattern over different surfaces (in order to create a magnetic map) using both Hall sensors for high field detection and AMR sensors for low field detection.
Force measurements using piezoelectric polymer films or force-sensitive films
In some industrial applications, the space where the force measurements have to be made is small. In such cases, thin force-sensitive films can be used. We are working both with piezoelectric polymer films for dynamic force measurements and resistive force-sensitive films for static force measurements.
Magnetic finite element analysis
In the electromagnetic sensor group, we are also working with magnetic simulations using Finite Element (FE) analysis. With our knowledge of, and experience with, magnetism, magnetic-material properties and FE analysis, we are good partners for solving magnetic-application problems using magnetic FE analysis.