Mounted resonant frequency of an accelerometer
Mounted resonant frequency is the point in frequency in the accelerometer’s frequency response where the accelerometer outputs maximum sensitivity. It is specified in units of hertz (Hz). Typical accelerometers exhibit a mounted resonant frequency above 20 kHz, although some show as high as 90 kHz. As the name implies, it is the result of the natural resonance of the mechanical structure of the accelerometer itself. [Certainly if the resonance of the accelerometer were measured in “free space” it would be different than if mounted to a structure. However, this is an impractical application for a piezoelectric accelerometer , thus the designation “mounted” is added.] It is not a design goal of manufacturers to produce an accelerometer that has a mounted resonant frequency within a certain tolerance. Instead, mounted resonant frequency is specified as a minimum, ensuring to the user that this resonant point will not occur below the minimum. As such, mounted resonant frequency is a rough “figure-of-merit” that sets the upper limit of the frequency bandwidth of the accelerometer .
For piezoelectric accelerometers, whose mechanical structure is almost completely undamped, the amplitude of the resonant peak can be quite high, resulting in a sensitivity many times higher than the specified reference sensitivity. As such, any vibration at or near the frequency of the resonant peak will be highly amplified, resulting in distorted measurements and corrupted data. A design goal of manufacturers, then, is to push the mounted resonant frequency point as high as possible in the accelerometer’s structure, with the intent that the point be well beyond any vibration frequencies in the user’s measurement application. The user also has to ensure that no vibration frequency components are at or near the mounted resonant frequency point.
Note that mounted resonant frequency is specified assuming ideal accelerometer mounting conditions. Just as the manufacturer can influence the mounted resonant frequency point with the accelerometer’s mechanical structure itself, so too can external structural factors (which the user controls). As mechanical 
resonance characteristics in general are dependent on material stiffness and damping, it is critical the accelerometer be mounted correctly and as stiff as possible. Improper mounting generally decreases stiffness and increases damping, causing the resonant peak to decrease in frequency and the width of the resonant rise to increase (i.e. mechanical Q is lowered). The ultimate result of this will, if allowed to degrade enough, affect the frequency response of the accelerometer.
-
We strive to provide our customers with an excellent shopping experience every single time and... Read Full Story » -
TrueMASS is a leading distributor of precision calibration weights and weighing instruments. Our... Read Full Story » -
The weighing scales are amongst the most essential tools that are used for measurement. It is... Read Full Story » -
Advanced microphones, such as those developed by Endevco, are used for the measurement of high... Read Full Story » -
The ENDEVCO® Model 8511A is a rugged, piezoresistive pressure transducer for high pressures. It... Read Full Story »
