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Page 486 of 977 Results 4851 - 4860 of 9762

S. Downes, A. Knott, I. Robinson
DETERMINATION OF PRESSURE TRANSDUCER SENSITIVITY TO HIGH FREQUENCY VIBRATION

This paper reports on an investigation into the sensitivity of one type of piezoelectric pressure transducer to the acceleration of its support mount, when located in the end wall of a shock tube and subjected to a very fast pressure step. Support mounts of different materials are used, together with laser vibrometry measurements of the back face of the mount, in an attempt to separate the part of the signal due to the acceleration from that due to the pressure step.

M. N. Medina, J. L. Robles, J. de Vicente
REALIZATION OF SINUSOIDAL FORCES AT CEM

This paper describes the procedure implemented at CEM for dynamic force calibration using sinusoidal excitations of force transducers. The method is based on a sinusoidal excitation of force transducers equipped with an additional top mass excited with an electrodynamic shaker system. The acceleration is measured by means of a laser vibrometer

S. A. Aye, P. S. Heyns, C. J. H. Thiart
SLOW ROTATING BEARING CONDITION ASSESSMENT BASED ON BAYESIAN GAUSSIAN MIXTURE REGRESSION

This paper presents the condition monitoring of slowly rotating bearing using experimental data from acoustic emission signal. The condition monitoring methodology is based on a nonlinear parametric Bayesian technique, Gaussian Mixture Regression which is expected to accurately diagnose bearing damage under fluctuating load and speed conditions. The proposed model has the ability to model high dimensional or multi-modal data and retains the flexibility of nonparametric approach. Therefore, the Gaussian Mixture regression method is applied to the condition monitoring of slowly rotating bearing in this study. Results show that the GMR approach is an appropriate, powerful, cost effective and an easy-to-tune regression technique for monitoring and predicting slowly rotating bearing damage under fluctuating speed and loading conditions.

Torben R. Licht, Sven Erik Salboel
0 Hz AND LOW FREQUENCY CALIBRATION OF LOW FREQUENCY REFERENCE ACCELEROMETERS

During the last decade more and more interest has been found in making low frequency vibration measurements. One area that has driven this is the earthquake studies, but here accuracy is not a focus point. However when we start to look at large structures like wind turbines, large aircrafts with 60 to 80 m wingspan, bridges and 400 to 500 m towers the accuracy becomes vital. These large structures have vibration modes in the range 0.3 to 1 Hz.
The method for Primary vibration calibration by laser interferometry using quadrature outputs described in ISO 16063-11 can be extended down to 0.1 Hz today thus giving the foundation for accurate measurements in the low frequency (LF) range.
It is however desirable to link these results that are obtained at very low vibration levels and frequencies to measurements at 0 Hz with constant acceleration of about 9.8 m/s².
This method is basically described in ISO 5347-5 (to be revised as ISO16063-16) but a detailed description of uncertainty budgets is not given.
Recently the Danish Primary Laboratory of Acoustics (DPLA) participated in the first international comparison covering the LF range of vibration, and in that context we decided to make a 0 Hz calibration with relatively simple means but exploiting the fact that the local Gravity today can be determined by an uncertainty of about 10-8.
By using a transfer technique and without utilising the full potential we could make an uncertainty budget with an expanded uncertainty of about 0.04% on a servoaccelerometer calibration, where one of the main contributions turned out to be thermal drift.
The experience we got during this calibration and the uncertainty budget created will be presented.

F. Larsonnier, G. Nief, P. Dupont, P. Millier
SEISMOMETERS CALIBRATION: COMPARISON BETWEEN A RELATIVE ELECTRICAL METHOD AND A VIBRATION EXCITER BASED ABSOLUTE METHOD

Considering the vibration metrology field, seismometers calibration is a challenge because of low frequency, and the heavy mass of the sensors. The CEA designs short period horizontal and vertical ground velocity measurements single axis seismometers, uses, and maintains them in operational condition. Their response is calibrated with an electrical method during their operational life to ensure that they fulfil their technical requirements. Thanks to the PTB multi-component exciter we calibrated an horizontal and a vertical short-period seismometers as well as a STS-2 according to the ISO 16063 standard method. The author presents a comparison of the two methods and the associated results.

Gustavo P. Ripper, Ronaldo S. Dias, Giancarlo B. Micheli, Cauê D. Ferreira
CALIBRATION OF IEPE ACCELEROMETERS AT INMETRO

This paper discusses the calibration of IEPE accelerometers. The use of these low-impedance output transducers is growing fast worldwide and therefore the demand for their calibration is increasing proportionally. Since many secondary calibration laboratories are more experienced with calibrating high impedance charge output accelerometers, we frequently receive questioning about how to properly calibrate the IEPE models. Some experimental results are presented herein and the effects of some sources of error that can be present during a calibration process are discussed.

W. Kokuyama, T. Watanabe, H. Nozato, A. Oota
DEVELOPMENT OF ANGULAR VELOCITY CALIBRATION FACILITY USING SELF-CALIBRATABLE ROTARY ENCODER

A novel type of angular velocity calibration standard is under development at NMIJ. The system is equipped with a self-calibratable rotary encoder (SelfA), which is same apparatus as one of the national angle standards in Japan. SelfA is also useful to ensure angular traceability in a simple and robust way. This facility will be mainly utilized to provide angular velocity standard for MEMS gyroscopes which become widely used in automobile industries. In this paper, demands for angular velocity standard, advantage of using a SelfA and initial experimental results of the facility will be presented.

Jeffrey Dosch, Mark Schiefer
VIBRATION-BASED METHODS FOR EVALUATING LINEARITY OF DC-COUPLED VIBRATION ACCELEROMETERS

This paper describes a shaker technique for measuring nonlinearity of accelerometers. The method has application to acceptance testing of DC-coupled accelerometers where the use of a centrifuge is cost prohibitive. To demonstrate the utility of shaker-based methods, nonlinearity tested by both centrifuge andshaker is compared.

H. Volkers, T. Beckmann, R. Behrendt
INVESTIGATIONS OF REFERENCE SURFACE WARP AT HIGH SHOCK CALIBRATIONS

This paper describes the investigation of transducer reference surface warping during high shock calibrations using a Hopkinson bar and two laser Doppler vibrometer (LDV) and one LDV in conjunction with a laser Doppler scanning vibrometer. Dipole shocks up to 80 km/s² where applied to transfer standard back to back accelerometers with and without mass loads.

López Iris, Silva Guillermo, Ruiz Arturo
CALIBRATION OF NON CONTACT VELOCITY SENSOR USED IN AUTOMOTIVE INDUSTRY

This paper includes a description of the calibration method used at CENAM to calibrate non contact velocity sensors, which are used by the automotive industry for velocity measurement of vehicles, and distance measurement calibration also used to perform odometer testing. The calibration system development at CENAM consists of a rotor steel of 400 mm diameter with an inertial mass that keeps a constant velocity at the system, a photoelectric probe, a stroboscope and a universal frequency counter. The rotor is driven by an electromechanical control. The velocity measurement is performed in the range from 10 km/h to 190 km/h, distance measurements from 50 m to 2 000 m are also carried out. The final obtained results and the associated expanded uncertainty are reported.

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