Microfabricated inductive linear micro positioning sensor

The inductance of an inductive device with a moving core changes as a function of the core position. By extending this principle to a microtransformer with multiple, evenly spaced cores, a measurement system combining features of analog (variable reluctance) and incremental positioning may be devised. For detecting the direction of motion (to know in which direction to count), an incremental length measurement system requires not just one, but two output signals, which have to be offset by 90 degrees. The paper presents a microtransformer based positioning system fulfilling these requirements. It presents the fabrication technology employed and discusses experimental test results.