History, Working Principle, and Pitfalls of IEPE/ICP Piezoelectric Sensors

This article reviews the operating principles of IEPE/ICP accelerometers, which are the prevailing standard for vibration and acceleration measurements, and examines two pitfalls that can compromise measurement accuracy: soft-clipping and temperature sensitivity. Soft-clipping, a non-linear amplitude response, occurs when the internal electronics of an IEPE/ICP sensor exceed their specified linear operating range, typically corresponding to an output of $\pm\SI{5}{\volt}$. Because most measurement systems allow a wider voltage range of $\pm\SI{10}{\volt}$, this non-linear behavior can occur without triggering system-level warnings. Shaker tests indicate that prolonged operation beyond the rated measurement range results in significant signal distortion, particularly attenuating negative acceleration values and producing asymmetric signals. Even after returning to nominal operating conditions, a recovery time of several seconds is required. While the soft-clipping effect appears largely frequency independent up to \SI{5}{\kilo\hertz}, it may be difficult to detect in real-world vibration tests with complex, broadband signals. Impact tests further reveal that soft-clipping subtly affects shock responses, primarily altering initial peaks and potentially obscuring high-frequency modes that decay rapidly. In contrast, frequency-domain analyses are less affected. Additionally, temperature tests show that sensor sensitivity can vary substantially, highlighting the importance of temperature monitoring or the use of thermally compensated sensors. Overall, the findings emphasize that avoiding operation outside the rated measurement range and implementing appropriate monitoring or warning strategies are essential for reliable IEPE/ICP measurements.