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I've been reading about a linear displacement sensor known as a Linear Variable Inductance Transducer (LVIT). This uses a movable conductive shield over a coil to modify the inductance. The shield is referred to as a "spoiler".

Note the spoiler is nonferrous, eddy currents are created in the spoiler, which I assume decreases the inductance compared to a free standing coil.

My question is how much does moving the spoiler onto the coil change the effective inductance? Is it likely to be approximately linear to the position?

Online coil calculator like Coil32 allow me to model a single-layer coil, but do not assume any sort of spoiler is present.

Burt_Harris
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  • Model it as a transformer, with the secondary shorted, and fairly poor mutual coupling. Moving more of the spoiler over the coil increases the coupling. –  Dec 09 '20 at 21:02
  • OK, seems like I need to model the self-inductance of the spoiler, but it's not round wire. Let's say the spoiler is an aluminum tube 100 mm long, 10 mm outside diameter, inside diameter 8mm. – Burt_Harris Dec 09 '20 at 22:27

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