Accelerometer Selection


Cost vs performance tradeoff


Accelerometer selection involves a tradeoff between performance and cost, with performance measured by dynamic range, noise floor or resolution. Dynamic range (DR) is the ratio of the largest to the smallest signal recordable, expressed in dB (decibels). Each 20 dB is a factor of 10 and each 10 dB is a factor of 3. If an accelerometer has a range of 4g and a dynamic range of 70 dB, the noise floor is 4g/3000 = 1.3 mg. Signals below 1.3 mg are not visible. The cost of an accelerometer increases with DR, so specify an accelerometer with a DR appropriate for the application.

Accelerometer characteristics


Accelerometers are often triaxial and used to sense seismic, strong-motion and earthquake acceleration. Accelerometers also can measure building resonance vibrations in
structure state-of-health applications. Some accelerometers have a self-test or calibration input obviating the need to remove the unit for testing. Most accelerometers are analog and can be used without programming.

Accelerometer options


The
Accel-70 and the Accel-90 are MEMS (Micro Electro Mechanical Structure) devices. The Accel-120 is a force-feedback accelerometer (FBA) using magnetics to sense acceleration. MEMS devices are manufactured like integrated circuits so are less costly but lack the FBA's DR. The accelerometers below are DC response so measure gravity and are easily calibrated with a "tilt" test. AC-response accelerometers cannot measure static acceleration (gravity) and require an expensive "shake table" to be calibrated.


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