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Strip measurement inductive SMI

The measuring principle of the SMI sensor family (Strip Measurement Inductive) is based on electromagnetic induction. Two centre sensors are arranged at the strip edges at right angles to the strip pass line level and symmetrically to the system centre, and they are configured in such a way that the strip passes between the sensors as centrally as possible. The centre sensor that is located above the strip functions as a transmitter and the opposite sensor functions as a receiver.

The SMI2.11.x electronic unit supplies the transmitters with a sinusoidal alternating current voltage, which is regulated in terms of its frequency and amplitude. At each transmitter coil, a distinctive electromagnetic alternating field is formed and directed towards the opposite receiver. The receivers detect a different intensity of the alternating field, 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 level.

The inductive measuring system contains complex self-monitoring facilities. The individual signals are combined into the collective messages "Measuring equipment OK" and "Strip detected". 

In addition to the proven performance features 'freedom from maintenance' and 'stability', the new modular sensor design as well as the improved symmetry characteristics of the SMI sensor family offer a better centre measuring accuracy as well as various possibilities to achieve your individual demands.

Since it is unsusceptible to disruptive external influences, even non-magnetic materials such as aluminium, copper, brass and austenitic chrome nickel steels (e.g. 1.4301) are also reliably detected with the SMI system.

Customer Benefits:

  • A wide area of application ranging from 0.05 mm to 16 mm strip thickness (others available on request) 
  • Sensors are insensitive to:
    • Changing insulation resistance due to dust accumulation on the measuring equipment
    • Disturbance of the static field, e. g. in the case of inspection tours by system personnel
    • Water, steam and metallic fumes produced during treatment
    • Dust which contains tinder and metal that is produced during machining
    • Ionising furnace atmospheres

EMG's family of inductive sensors includes the following models and solutions:


A summary including various technical details can be found in our product brochure. We would be happy to provide you with comprehensive assistance in developing your optimum solution! Contact us!

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