Amplitude Linearity of an accelerometer
Amplitude linearity is a measure of how linear the output of an accelerometer is over its specified amplitude range. It is sometimes called amplitude non-linearity, since it specifies the deviation from perfect linearity. Ideally, an accelerometer would have exactly the same sensitivity at any amplitude point within its specified amplitude range. But with a real accelerometer, this is not the case. So amplitude linearity specifies the limits to how far the accelerometer’s output will differ from this perfect linearity. Note that amplitude linearity is only valid at a (usually undisclosed) single frequency.
There are several ways to specify amplitude linearity. The most restrictive is to specify percentage of reading, typically ±1% over the entire full scale range. This is a close tolerance specification, as it means the accelerometer’s sensitivity cannot vary by more than ±1% at any point in the amplitude range. A much less restrictive way is to specify linearity in a piecewise manner, such as this example: sensitivity increases 1% per 500 g, 0 to 2000 g. This means that at the top end of the amplitude range, sensitivity can vary as much as 4% from that at the low end of the amplitude range.
Amplitude linearity errors cause signal distortion, particularly in high amplitude accelerations. In environments where multiple vibration frequencies are present, intermodulation distortion can result, creating frequencies in the instrumentation that were not present mechanically at the accelerometer.
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