I was wondering if there is any way I could use an electromagnet to detect the presence of a permanent magnet.
I am specifically thinking of using a planar type small coil. Maybe use a core or something that can get saturated by the permanent magnet field.
Do let me know if someone has experience doing something similar. Thank you.
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1\$\begingroup\$ You are kind of describing the operation of a fluxgate magnetometer. \$\endgroup\$– virCommented Jan 3 at 2:40
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2\$\begingroup\$ Simple LC oscillator can be stopped if a perm. magnet is placed near its coil. The key is to drive LC with very low currents, otherwise PM does not affect the oscillations. \$\endgroup\$– Michal PodmanickýCommented Jan 3 at 4:04
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\$\begingroup\$ @MichalPodmanický I've never heard of that. Do you have a link? \$\endgroup\$– Math Keeps Me BusyCommented Jan 3 at 4:12
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\$\begingroup\$ @MathKeepsMeBusy I have any, but I did it physically many times. Theres even possible to detect magnetic field of Earth. Best is to use oscillator with parallel LC tank with high L and small C (relatively). \$\endgroup\$– Michal PodmanickýCommented Jan 3 at 4:23
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1 Answer
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The permanent magnet only has a measurable effect when the magnetic field changes, i.e., when you move the magnet relative to the windings (where you basically build a generator), or as you propose, when you feed the electromagnet with a changing current and the materials are driven into nonlinear regions. But that would mean you need to waste a lot of power, and would still need pretty sensitive and complicated control and readout electronics.
This is a classical use case for a Hall effect sensor. That simply measures the Lorentz force on charge carriers traveling through a semiconductor disk.
answered Jan 3 at 2:25