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Manufacturing an accelerometer that uses piezoresistance first starts with a semiconductor layer that is attached to a handle wafer by a thick oxide layer. The semiconductor layer is then patterned to the accelerometer's geometry. This semiconductor layer has one or more apertures so that the underlying mass will have the corresponding apertures.
The charge signals at the input of a charge amplifier can be as low as some fC (FemtoCoulomb = 10 −15 C). A parasitic effect of common coaxial sensor cables is a charge shift when the cable is bent. Even slight cable motion may produce considerable charge signals which cannot be distinguished from the sensor signal.
Piezoelectric sensors which do not possess IEPE electronics, meaning with charge output, remain reserved for applications where lowest frequencies, high operating temperatures, an extremely large dynamic range, very energy saving operation or extremely small design is required.
For accelerometers, a seismic mass is attached to the crystal elements. When the accelerometer experiences a motion, the invariant seismic mass loads the elements according to Newton's second law of motion =. The main difference in working principle between these two cases is the way they apply forces to the sensing elements.
An accelerometer measures proper acceleration, which is the acceleration it experiences relative to freefall and is the acceleration felt by people and objects. [2] Put another way, at any point in spacetime the equivalence principle guarantees the existence of a local inertial frame, and an accelerometer measures the acceleration relative to that frame. [4]
Electrical charges interact via a field. That field is called electric field.If the charge doesn't move. If the charge moves, thus realizing an electric current, especially in an electrically neutral conductor, that field is called magnetic. Electricity can be given a quality — a potential. And electricity has a substance-like property, the ...
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This is fused with the gravity vector measured by the accelerometers in a Kalman filter to estimate attitude. The attitude estimate is used to transform acceleration measurements into an inertial reference frame (hence the term inertial navigation) where they are integrated once to get linear velocity, and twice to get linear position. [8] [9] [10]