# Capactive accelerometer

1. Oct 2, 2010

### silvesterjang

The question is given.
1. (Capacitive accelerometer) In this problem, we would like to understand the capacitance change of an accelerometer shown below. Blue area represents movable conductive silicon material with a thickness of h. Red area represents anchored silicon areas. Assume that the parasitic capacitance is negligible, and the gap distance ‘g’ is much smaller than other dimensions in the figure.

at first this question want to get the answer, capacitance between A and B

and second, the accelerometer gets accelerated, and the movable part is displaced by ‘x’ to the left side. It is known that the above structure has the spring constant of k. The mass of the movable part is m.

because of that capacitance is changed by moved part, how much does it changed?

(b) What is the capacitance between A and B?

(c) While the accelerometer is being accelerated with the same acceleration (x≠0), we applied the positive voltage V between A and B (V=VA-VB). Does the displacement increase or decrease? What is the new displacement? Explain your answer.

I don't understand this question, why do we get capacitance between A, B?
and where is 'two' capacitor which is connected?