http://en.wikipedia.org/wiki/Coriolis_effect

Deflection of a mass held by a beam due to the earths rotation.

Invensense is calling this a single axis "gyroscope".

It is not.

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It probably only works in the vertical axis so using three is out
of the question.

However these specifications are amazing.

500 degrees per second rotation is extraordinary!!!!!

Shock is 10,000 G's meaning it can be fired from a gun.
How about a guided cannon shell?

Sensitivity is 2 milli volt per degree per second. No question about
it!!!!!!!!!!! THIS IS AN ANGULAR ACCELEROMETER!!!!!!!!!!!!!!!!!!!!

A millivolts is 1/1000th of a volt. If max output is 3 volt the resolution
is one part in 1,500 !!!!! Extraordinary for something so cheap.

It is cheap enough to put in a toy.


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Here is another type of 3 axis accelerometer using a mass on a cantilever beam
but the capacitance change is sensed.

http://www.st.com/internet/analog/product/218132.jsp

"A proprietary process is used to create a surface micro-machined accelerometer. The
technology allows to carry out suspended silicon structures which are attached to the
substrate in a few points called anchors and are free to move in the direction of the sensed
acceleration. To be compatible with the traditional packaging techniques a cap is placed on
top of the sensing element to avoid blocking the moving parts during the moulding phase of
the plastic encapsulation."

"When an acceleration is applied to the sensor the proof mass displaces from its nominal
position, causing an imbalance in the capacitive half-bridge. This imbalance is measured
using charge integration in response to a voltage pulse applied to the capacitor.
At steady state the nominal value of the capacitors are few pF and when an acceleration is
applied the maximum variation of the capacitive load is in the fF range."

I microfarad is 100 million femto farads.

This uses a 12 bit A to D giving resolution of one part in 4096 or 0.000244%

Paul Lamar