How Do Resonant MEMS Accelerometers Detect Changes in Acceleration?

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Resonant MEMS accelerometers detect changes in acceleration by utilizing a resonating beam that creates a standing wave pattern when an AC voltage is applied at its natural frequency. When an external acceleration disrupts this standing wave, a feedback circuit is activated to restore the beam to its original frequency. The effort required to reestablish the standing wave correlates directly with the magnitude of the applied acceleration. Understanding the frequency matching of the AC voltage to the beam's natural frequency is crucial for accurate measurements. Additionally, thermal effects must be considered to ensure precision in readings.
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Hello,
Suppose that I have a resonant MEMS accelerometer. It has a suspending beam (resonator) and I want to apply an AC voltage to the beam which will be at beam's resonant(natural) frequency.
When I do this, I will create a standing wave pattern of acoustic waves (vibrations) inside the resonant beam. If an external force (or acceleration) is applied on my accelerometer, the standing wave pattern will disappear. However, I will use a feedback circuit to bring the resonator back to its natural frequency so that the standing wave pattern will re-emerge. The amount of "effort" I provide to restore the standing wave pattern (to bring beam back to its original resonant frequency) will be a measure of applied acceleration.

How does the circuit understand if the standing wave pattern is distrupted by an applied acceleration?

How do I experimentally understand that I am applying an AC voltage which has the same frequency as the natural frequency of the beam?
 
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