Correction of shaker flatness deviations in very low frequency primary accelerometer calibration

Abstract

This paper describes the influence of a constant curvature of the shaker's air bearing guidance on a low frequency primary accelerometer calibration. Based on the mathematical model, three different methods are developed that allow a quantitative evaluation of this disturbing effect and thus the correction of the resulting systematic deviation.All three methods are applied to the example of a primary low frequency accelerometer calibration performed at PTB, and the results are given in comparison to the original uncorrected magnitude of sensitivity results.

Reduction of gravity effect on the results of low-frequency accelerometer calibration

“…The correction procedure proposed by PTB have also been tested by INMETRO. Figure 1 presents corrected sensitivity results obtained according to the method proposed by Bruns and Gazioch using the same coefficient published by PTB in [3]; using the coefficient determined by INMETRO for its system; original certificate results obtained in 2018 and in 2019; and results with 3 screws loosened at one side the linear guide. Therefore, it was decided to quantify the effect caused by this process and take actions in order to improve the straightness of the guide.…”

“…The application of a mathematical correction of the systematic error caused by gravity had been proposed by T. Bruns and S Gazioch in 2016 [3]. We preferred to attack the problem following a different approach.…”

Digital signal processsing functions for ultra-low frequency calibrations

“…How well the COP and COA works is estimated by representing , and from equation (1) and (2) with simulated data. Here the signal is a multi-sine with = 1 … frequencies ( ) and phases ( ), all with amplitude 0:…”

Monocular Vision-Based Earth’s Graviation Method Used for Low-Frequency Vibration Calibration

“…However, the sensitivity phase calibration accuracy is only 0.5° which is insufficient for the high-accuracy calibration when the frequency is > 0.3 Hz. Furthermore, the sensitivity phase and magnitude calibration accuracy by LI are significantly decreased because the excitation acceleration provided by the shaker with a limited stroke leads to the low SNR output signal of the accelerometer when the frequency is < 0.3 Hz [12][13]. The Earth's gravitation (EG) method described in [14] uses a rotator to provide the sinusoidal excitation acceleration at a constant highamplitude to the accelerometer, which avoids the small excitation acceleration of LI when the frequency is < 0.3 Hz.…”