Single Point Vibration Measurement

This application note describes the use of SmarAct’s PICOSCALE Interferometer for single-point vibration measurement of a cantilever, demonstrating its capability to achieve high-resolution, contact-free displacement sensing. With a sub-atomic noise floor and high bandwidth, the PICOSCALE system effectively captures both thermal and induced vibrational modes, making it ideal for research and industrial applications requiring precise vibration analysis.

Problem: Characterizing minute vibrations, particularly those influenced by thermal and mechanical excitation, is crucial in many scientific and industrial applications. Conventional vibration measurement methods often lack the sensitivity and range to accurately detect both micro and macro-level displacements in materials with low reflectivity. A high-resolution, non-contact solution is needed to achieve precise vibration measurement in such challenging scenarios.

Solution: The PICOSCALE Interferometer provides a solution by enabling contact-free, high-resolution displacement measurements with a low noise floor, using a laser-based Michelson interferometry setup. This technology ensures accurate data capture even on low-reflectivity materials like silicon, commonly used in micro-cantilevers.

Implementation:

1. Setup: The experiment involved a PICOSCALE F01-10 focusing sensor head directed at a tungsten cantilever mounted on a piezo stack, allowing both passive and active vibration testing.
2. Measurement: Initially, the cantilever’s natural vibrations were recorded under ambient conditions. Subsequently, its resonance was actively excited by driving the piezo stack at the cantilever's eigenfrequency (2119 Hz).
3. Analysis: The vibration data was processed using Fast Fourier Transform (FFT) functions within the PICOSCALE graphical user interface to identify and quantify the frequency components of the displacement signals.

Results: The system successfully detected a thermal resonance peak at around 2100 Hz, attributed to natural ambient excitations. When the piezo actuator was driven at the cantilever's resonant frequency, a pronounced peak emerged in the FFT, confirming the system’s effectiveness for both ambient and induced vibration analysis. The PICOSCALE demonstrated its precision and suitability for diverse applications in fundamental R&D as well as process control in industrial settings.