Invited article: Expanded and improved traceability of vibration measurements by laser interferometry

Area of Science:

• Metrology and Measurement Science
• Mechanical Engineering and Acoustics
• Instrumentation and Sensor Technology

Background:

• Traceability to the International System of Units is crucial for vibration and shock measurements, impacting product quality, health, and safety.
• International standards, such as the ISO 16063 series, increasingly incorporate advanced laser metrology techniques for calibration.
• Existing standards (ISO 16063-11:1999) define interferometric methods for primary calibration of accelerometers up to 10 kHz.

Purpose of the Study:

• To investigate the applicability of established interferometric calibration methods for laser vibrometers in an expanded frequency range.
• To support the development of new international standards (ISO 16063-41:2011) for laser vibrometer calibration.
• To achieve measurement uncertainties compliant with international standards at significantly higher frequencies.

Main Methods:

• Generation of steady-state sinusoidal vibrations using piezoelectric actuators up to 347 kHz.
• Measurement of displacement amplitude (158.2 nm) using standardized interferometric techniques: fringe counting and sine-approximation.
• Simultaneous application and comparison of three interferometric methods to assess deviations and uncertainties.

Main Results:

• Deviations between the three applied interferometric methods were consistently below 1%.
• Measurement uncertainty limits specified in ISO 16063-11 (1 Hz to 10 kHz) were maintained at frequencies orders of magnitude higher.
• The uncertainty limit of 0.5% at 160 Hz was not exceeded even at 160 kHz, demonstrating high-frequency accuracy.

Conclusions:

• The study validates the use of interferometric methods for laser vibrometer calibration across an expanded frequency range, up to 0.5 MHz.
• Refined techniques and procedures enable the application of these methods beyond the initially specified ranges in international standards.
• The findings directly contributed to the specifications and procedures outlined in ISO 16063-41 for rectilinear laser vibrometer calibration.