Methodological Scope
Primary calibration of vibration and shock transducers often utilizes laser interferometry to ensure the highest degree of accuracy in measurement. The iso 16063-13 standard specifies the methods and requirements for the primary shock calibration of accelerometers using these optical techniques. It defines the procedure for determining the sensitivity of a sensor by comparing its electrical output to the mechanical input measured by a laser.
This standard applies to a range of peak accelerations and pulse durations, providing a rigorous framework for national metrology institutes and high-end laboratories.
Velocity Magnitude
Measurement of the Doppler shift in the reflected laser light allows for the precise calculation of the surface velocity of the transducer. The iso 16063-13 protocol requires that the time-dependent velocity be integrated to find the displacement or differentiated to find the acceleration. High-speed data acquisition systems capture these waveforms with enough resolution to characterize shocks lasting only a few microseconds.
Interferometric Principle
Heterodyne or homodyne interferometers provide the optical signals that the standard requires for the calculation of mechanical motion. These systems are immune to many of the mechanical resonances that plague traditional back-to-back calibration methods. By using the wavelength of light as a reference, iso 16063-13 ensures that the measurement is traceable directly to the definition of the meter.
Error Analysis
Calculation of uncertainty must account for the noise in the photodetector and the alignment of the laser beam. The iso 16063-13 standard provides a detailed guide for estimating these components to produce a final calibration certificate.
