The acting force or the torque impacting on the shaft may cause proportional change of the direction of the magnetic field inside the shaft. This is detected by means of high-resolution magnetic field coils positioned at a distance of upto 3mm from the shaft.

For the purpose of differential measurement at least one couple of coils is required, and each coil of the pair detects one of the two opposed magnetic fields.

The higher the requirements in respect to accuracy, the greater the number of coil couples placed around the coded area of the shaft (generally up to 4). The coils are set on coil-boards i.e. fixed firmly in respect to the shaft.

For protection against external magnetic interference the coil carrier is generally integrated in an additional housing which, besides the differential modus, also serves as an extra shield.

The magnetic field coils, the coil carrier and the shield compose a unit which represents the secondary sensor.

We now invite you to read how the signals of the secondary sensor are processed in our electronics.