How Do Resonant MEMS Accelerometers Detect Changes in Acceleration?

[Edge5]

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?

 

[berkeman]

Interesting, I hadn't heard of this modality before. It looks like you also need to take thermal effects into account to stay accurate in the readings:

https://mems.eng.uci.edu/files/2018...eter-With-Continuous-Thermal-Compensation.pdf