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Seung-Hwan Nam, Yong-Bong Lee, Wan-Sup Cheung
METHOD OF CALIBRATING CHARGE AMPLIFIERS USING A DYNAMIC SPECTRUM ANALYZER

This paper proposes a simple and salient method of calibrating the charge amplifier required for the primary and/or comparison calibration of vibration and shock transducers. The proposed method exploits the ‘sinesweep’ measurement for evaluating the frequency response function (FRF) between the input and output signals using a dual-channel dynamic spectrum analyzer. The principle and theoretical model for the calibration of charge amplifiers are presented. The uncertainty evaluation models for the gain and phase shift are described. Experimental results unveil that the standard uncertainties of the gain and phase shift are less than 0.035 % and 0.05° over the frequency range of 1 Hz to 10 kHz. Compared to the previous methods, one of the salient features of the proposed method is a simple calibration setup consisting of the standard air capacitor and the spectrum analyzer.

Wan-Sup Cheung
IMPROVED FEATURES OF ANGULAR VIBRATION EXCITERS

This paper introduces main features of an improved angular exciter model focused on the angular vibration calibration and performance tests of MEMS gyroscopes. The improved model has extended more capacity of generating angular acceleration of 5,000 rad/s²- peak up to 1 kHz. Other features, such as the frequency response, the total harmonic ratios, and the load capacity will be introduced, in addition to the mechanical and electrical specifications.

Jiun-Kai Chen, Yu-Chung Huang, Hong-bo Hu
THE KEY COMPARISON FEASIBILITY EVALUATION BETWEEN LOW SHOCK AND HIGH SHOCK ACCELERATION CALIBRATION SYSTEM

The article is mainly to study the feasibility for comparing calibration results by different shock excitation systems. It analyzes the difference and causes for the calibration results of the same accelerometer by the two different excitation systems. It provides technical references for comparison among related shock standards. With the development of social and economic globalization, such comparison will play a significant role in calibration ability, international recognition and elimination of technical barriers to trade.

A. Ota, Y. Kobayashi, O. Takano, N. Kasai
DEVELOPMENT OF DIGITAL DEMODULATOR FOR LASER VIBROMETER STANDARD

In this study, a measurement reliability of commercial laser vibrometer with analogue demodulator is investigated for establishment of traceability system for laser vibrometer in vibration acceleration standard. As a result, a large amount of measurement deviation due to characteristics of analogue demodulator is confirmed, and in order to reduce such deviation, high accuracy digital demodulator, applicable as the reference standard, is developed. The good measurement accuracy of the developed digital demodulator was confirmed by the experiments.

H. Nozato, Th. Bruns, H. Volkers, A. Oota
AN INVESTIGATION OF SAVITZKY-GOLAY FILTERS FOR THE CALCULATION OF DERIVATIVES FOR PRIMARY SHOCK CALIBRATION

This manuscript reports about an investigation of two kinds of digital filters used for numerical differentiation of the displacement signal in the case of primary shock calibration of accelerometers. One is a 4th order Butterworth low-pass (4th BW) filter of infinite impulse response filters, and another is a Savitzky-Golay (SG) filter, which applies local polynomial approximation. The computational comparison was applied to low and high shocks using known analytical excitation functions. On the optimized condition of 4th BW and S-G filters, each sum of residuals was compared. As the result, the S-G filters showed for low and high shocks a better performance as low-pass filter than the 4th BW filters. In addition, the appropriate window width for the local polynomial approximation was derived.

H. Volkers, T. Bruns
THE INFLUENCE OF SOURCE IMPEDANCE ON CHARGE AMPLIFIER

This contribution discusses the influence of the source impedance on the complex sensitivity of a charge amplifier (CA). During calibration of a CA with varying source impedances deviations at higher frequencies were observed, which if not properly taken into account may generate systematic errors beyond the limits of the measurement uncertainty budget. The contribution discusses a model to describe the effect as well as an extension to established CA calibration procedures which allow to quantify and correct the effect.

Martin Brucke, Georg Siegmund, Christian Ehrmann, Uwe Bühn, Michael Mende
MEASUREMENT UNCERTAINTY OF HIGH-SHOCK CALIBRATION SYSTEMS

Applications that require measurements of shock type acceleration in an amplitude range above 100 000 m/s² are becoming increasingly more important in the industry. Thus also an accurate calibration of accelerometers used for such measurements is compulsory. This paper focuses on appropriate reference standards and the influence variables that determine the measurement uncertainty of high shock calibration systems using Hopkinson-bar shock exciters up to amplitudes of 2 000 000 m/s². What are the main variables that determine the measurement uncertainty? How can the uncertainty contributions of different reference sensors (laser vibrometer and strain gauges) be verified?
The paper aims to give an overview and also tries to identify where future research will be necessary to understand influence variables and optimize the measurement uncertainty of such high-shock calibration systems.

Chenguang Cai, Jingsheng Li, Lifeng Yang, Aibin Zuo, Qiao Sun, Hongbo Hu
FEASIBILITY OF VIBRATION SENSOR ON-LINE CALIBRATION WITH BUILT-IN CALIBRATION COIL

A kind of vibration sensors are widely used in seismic monitoring and environmental protection fields which have built-in calibration coils. But they could not be effectively calibrated or checked in the long term when they are placed on the monitoring locations. It is a choice to use the calibration coil to calibrate the senor on-line. In order to evaluate the feasibility, the sensitivities of the sensors are respectively calibrated by the low frequency vibration standard and calibration coils. The experiment results reveal the calibration coil method is effective in a certain frequency range depending on the dynamic characteristics of the structure of the sensor.

Gustavo P. Ripper, Giancarlo B. Micheli, Ronaldo S. Dias
A STUDY OF THE DISPERSION ON PRIMARY CALIBRATION RESULTS OF SINGLE-ENDED ACCELEROMETERS AT HIGH FREQUENCIES

This paper describes a study developed at INMETRO, which is focused on the evaluation of primary calibrations of single-ended accelerometers at high frequencies. It proposes a simple solution to reduce the dispersion on the sensitivity results evidenced when different vibration exciters are used. This can be helpful for calibration laboratories to compare results obtained in different systems. Therefore, the authors consider that it might benefit the process of both systems validations and interlaboratory comparisons.

M. Decker, K. Hintz, J. Nobis, C. Gühmann
CONTROLLING A DIESEL ENGINE WITH ENGINE MANAGEMENT BASED ON STRUCTURE-BORNE SOUND

An engine management system based on cylinder pressure provides the means to optimize, control and monitor the release of heat in any individual cylinder. The aim here is to reduce the resultant emissions as well as their scatter band. The paper demonstrates the relationships between structure-borne sound signals and cylinder-pressure signals using Wigner-Ville transformation. Subsequent feature extraction provides the capability of extracting features of combustion and injection that can be used in engine management. This makes it possible to replace cost-intensive cylinder-pressure sensor systems with structure-borne sound sensors that cost less and are more robust. Discourse concludes by presenting the results of engine management based on structure-borne sound and provides an outlook of further work.

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