Inductive Sensor

Working with two other engineers, I designed an inductive position sensor. This sensor uses eddy currents induced in a rectangular metal target to sense the position of the target relative to a "stretched coil". Such a coil is designed to have a varying field strength along the length of the coil. By forming a resonant circuit with the coil, one can measure the resonant frequency and observe the changing inductance, as the target moves along the coil. The final inductance value is read from the sensor over a USB cable to a laptop PC and mapped against a piece-wise linear calibration table to retrieve a position value.

Design achievements:

• 50um resolution
• 80mm linear input range
• Negligible sensor drift
• Absolute position measurement

Knowledge gained:

• Coil design
• Simulation with FastHenry2
• Hardware testing

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