Hi,
Define your range of frequency.
"Low frequency" does not mean anything.
There are natural "low frequencies" with 0.0000224 Hz ... and less ;-)
Is it accoustic (relative air pressure), mechanical force, or mechanical movement, or electrical...
As always: a simple sketch could help to clarify..
Klaus
Sure, that's why I suggested it. The advantage is easy calibration of measurement output.Are MEMS sensors are available in analog form?
Could you go the theremin route, and use the board's motion to modulate an ultrasonic or low-RF oscillator ?
Think 'metal detector'...
But I DO like the interferometer suggestion, provided you can sufficiently constrain your laser-diode's bandwidth.
FWIW, taken to tech-extreme, isn't this how LIGO & Co detect gravitational waves ?
The nice object about adhering magnet is amplifying the induced coil emf outputs a nice trace on a scope without any digital frameworks for sensor modules. I prefer keeping these things analog
A Forrest Mims book has an earth-movement sensor project exactly like you describe ('Science Projects' Mini-Notebook, pg 40-41). Suspend the magnet on a string. Position a coil of wire just below the magnet. Amplify the signal from the coil. The description says it can detect trains a mile away.
Perhaps it's all right if the magnet is placed on the moving surface, and the coil is suspended on fine wires, or a shielded cable.
How much does center hole diameter of an air coil crossover inductor coil type matter for picking up the oscillations?
For a coil, the article recommends a telephone pickup coil, or a 9V relay. Small is sufficient. The magnet has to jiggle easily, so it should be lightweight. Likewise it only requires a small coil (about the same diameter as the magnet) to interact fully with the flux field coming from the magnet's pole.
Do you plan to use a crossover (air) coil as commonly used in hi-fi speakers? Typical size is a few inches in diameter. It is under-utilized if you were to pair it with a small magnet.
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