Testing Methods for Verification of a Mounted Accelerometer Frequency Response

摘要

The mounted resonance frequency of an accelerometer is a key parameter to ensure a sensor's performance, its functional state, and how well the sensor has been mounted. The mounted resonance frequency leads directly to the frequency response limitation of a sensor, and how sensor sensitivity will change according to the frequency range of interest. The mounted resonance frequency can become a quite important property, and provides hints on the mounting conditions of a sensor and related issues. Some things that could be identified are, the accelerometer is loose from the mounting surface, the sensor's mass is too high in relation to the mass of the structure, or the mounting method lacks in stiffness. Under these various cross conditions, different resonance modes are theoretically expected from the solution of the equation of motion. The way to measure and specify such a parameter can be challenging. It is important to understand in which conditions this value has been determined when comparing one sensor to another, from one mounting method to another, from the sensor mass to unit under test mass ratio, or from a sensor's initial state to its response after several test cycles. In this paper we will provide you with an overview of the different procedures to perform such a resonance frequency test. We will then provide you with an understanding on a response if the measurement is performed on a free sensor hanging in the air, on a sensor mounted on a heavy structure, and with other intermediate mounting configurations. We will discuss different results obtained if the resonance frequency determination is performed using a shaker and performing a frequency sweep, using the pencil break test technique (similar to ASTM E976-84) or inverse piezoelectric excitation. We will then provide a rule of thumb on how to derive from those measurements an approximation of the sensor frequency response, if the damping properties of the sensor are known.