BMI
Inductive strip centre sensing
Inductive strip centre sensing is used for maintenance-free sensing of the position of metal strip within the framework of strip guidance systems. Non-magnetic materials such as aluminium, copper, brass and austenitic chrome nickel steels (e.g. 1.4301) are also reliably sensed by the inductive strip sensing system.
The sensing principle is based on electromagnetic induction. Two strip centre sensors are arranged on each strip edge at right angles to the strip pass direction and symmetrically to the centre in such a way that the strip moves centrally between the strip centre sensors. The strip centre sensor arranged below the strip is the reciever, and the sensor arranged above the strip is the emitter. An electronic unit feeds the emitters with a sinusoidal alternating voltage with controlled frequency and amplitude. On each emitter coil, a distinctive electromagnetic alternating field is formed and directed towards the opposite receiver. The receivers detect a different intensity, depending on the position of the strip. The alternating voltages induced in this manner provide analogue output signals for the strip edge position by evaluating the frequency-dependent amplitude.
The inductive strip sensing system contains complex self-test facilities. The individual signals are combined into the cumulative signals "Sensing system OK" and "Strip position OK".
