This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

[FAQ] Inductive Sensing Fundamentals Part 3: Ideal Target Distance for Inductive Sensing

Inductive sensing gives you the ability to use different coil sizes, coil frequencies, target sizes and materials. What is the ideal target distance?

  •  Inductive sensing relies on the interaction of the electromagnetic fields generated by the inductive sensor and the currents being induced on the conductive surface. It is important to recognize that the further the target is moved from the inductive sensor the eddy currents induced on the targets surface are reduced. Due to the distance, the target is only able capture a smaller portion of the electromagnetic field being generated by the inductive sensor. Since the electromagnetic field lines are generated by the inductive sensing coil then the field generated is directly proportional to the diameter of the inductive sensor. The targets ideal distance will depend on the inductive sensor’s diameter and can be calculated to be a percentage of the sensor’s diameter.

    Typically, at distance 20% or less will yield the highest sensitivity with the ability to detect micrometer changes. 21% to 100% will remain detectable but will suffer in sensitivity and measurement resolution. Past 100% it is out of the recommended sensing range.

                                                                                   

    For example, if we have a coil that is 20mm then the ideal target distance for high sensitivity would be up to 4mm of the inductive coil. From 5mm to 20mm would remain a detectable range but would have reduced in sensitivity. Anything beyond 20mm would be outside of the recommended sensing range.

    For more information please refer to the following documents:

    Inductive Sensing Touch-On-Metal Buttons Design Guide

    Inductive Touch Buttons for HMIs