IMEKO Event Proceedings

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Christiaan S. Veldman
Traceable Low Frequency AC Voltage Measurements
The International Organization for Standardization (ISO) has developed a set of standards for the calibration of vibration and shock transducers. Method 3 of ISO 16063 part 11, deals specifically with the primary calibration of accelerometers over the frequency range 1 Hz to 10 kHz. Many NMIs have implemented the method over a wider frequency range. One of the difficulties faced by said NMI, is the provision of traceable low frequency AC voltage measurements.
This paper considers low frequency AC voltage traceability options and investigates in more detail a measurement option defined as DC sampled AC measurements. As part of the investigation; 1) a calibration procedure is developed and implemented, 2) the measurement accuracy of the system is demonstrated.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Hideaki Nozato, Takashi Usuda, Akihiro Oota, Tamio Ishigami and Katsuhisa Kudo
Development of Shock Acceleration Calibration Machine in NMIJ
Calibrations of shock acceleration are industrially required from a view of human safety and product development. In NMIJ vibration group, a shock acceleration calibration machine (hereafter ‘calibration machine’) has been developed in response to much demand from Japanese industries, and can calibrate shock transducers in acceleration range from 200 m/s² to 5000 m/s². For primary calibration, accelerometer is calibrated by a combination of shock exciter and laser interferometer. In the shock exciter, shock acceleration is generated by rigid body collision between a hammer and an anvil. To avoid any disturbance motion, radial air bearing system is adapted to keep high stiffness in perpendicular directions to the collision. The hammer, supported by the air bearing, is accelerated by an air gun and collides with the anvil through a rubber pad. Thus, acceleration waveform of the anvil strongly depends on viscoelasticity of the rubber pad. Different hardness of the rubber pad is examined to realize various peak accelerations. As another significant issue, optimization of low-pass digital filter is necessary to obtain reliable acceleration waveforms. This manuscript reports not only a procedure of low-pass digital filtering but also cut-off frequency dependence of low-pass digital filter on peak acceleration.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Yeu-Jong Huang, Chao-Jung Chen, Sheng-Hang Wang, Kuang-Yih Tsuei, Henner Baitinger, Christian Walter
Dynamic Structure Evaluation of Isolation Seismic Block for Primary Vibration Calibration System
According ISO 16063-11 the exciter and interferometer of primary vibration calibration system must be mounted on heavy seismic block so as to prevent unwanted vibration from having effects on the calibration results. To improve the current low frequency primary vibration calibration system National Measurement Laboratory (NML) design and manufacture a new heavy seismic block. The new block which is made of case iron and its mass is about 4000 kg. The block’s dimension is 2000 mm × 600 mm × 700 mm. In order to evaluate the block dynamic characteristic we apply experimental modal method and get its first mode frequency is 314 Hz which is bigger than calibration working frequency 0.5 Hz to 70 Hz. In the other hand we want to isolate the environmental ground vibration like people walking, rotary machine, air condition etc., the block is placed on three proper designed isolators. The whole block system natural frequency should avoid the working frequency as much as possible. By using hammer to test the natural frequency of block system, we get natural frequency is 15.25 Hz for the horizontal direction of the block. From the result the block system will have effective isolation. Finally we apply the exciter to produce acceleration with different frequency and also measure the acceleration on interferometer system to compare the acceleration value between them. We find the acceleration ratio of interferometer to exciter is less than 0.0005 at most frequency. As above mention the seismic block has a perfect performance that is calibration system uncertainty component will be reduced due to unwanted vibration.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Christian Hof, Michael Kobusch
Comparison of the Calibration of a Heavy Multi-Component Vibration Transducer on Different Exciter Systems (Calibration of Heavy Triax-Transducer)
The performance specifications of a shaker may be strongly affected by the load which it is driving. When using a shaker for calibration purposes, the mass and mass distribution of the device under test as well as its mounting configuration may deteriorate seriously the purity of the motion of the shaker armature along the desired axis. In this paper the authors present an attempt to reduce the magnitude of parasitic movements by an improved mounting configuration. Although the resulting motion is significantly improved, transverse, bending and rocking acceleration could not be diminished to less than 10 % as recommended by the ISO standard. In spite of this unsatisfactory large resulting parasitic motion, a reasonable calibration of a device under test is nevertheless possible when selecting carefully the axis of the reference laser vibrometer. We were able to validate this approach by a comparison with a calibration carried out on an alternative vibration exciter of inherently better quality (but considerable higher cost).
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Takashi Usuda, Akihiro Oota, Hideaki Nozato, Tamio Ishigami, Yasuhiro Nakamura, and Katsuhisa Kudo
Development of charge amplifier calibration system employing substitution method
Charge amplifier is a key device for vibration metrology as well as an accelerometer itself. Reliability of vibration measurement heavily depends on the stability and frequency characteristics of charge amplifier. Especially, phase characteristic of charge amplifier becomes more important as many calibration sectors have adopted Sin-approximation method which enables calibration of accelerometer phase shift.
In this paper, development of charge amplifier calibration system both for amplitude (gain) and phase is reported. The calibration system consists of standard capacitor, inductive voltage divider, injection transformer, and sine signal generator. Because the system does not contain any active device such as voltmeter or A/D converter which requests periodic calibration, it is quite stable and reliable without any maintenance including periodical calibration. The system enables calibration uncertainty of 1.3·10^-3 % in gain and of 6·10^-5 deg. in phase shift at 160 Hz.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Gustavo P. Ripper, Guilherme A. Garcia, Ronaldo S. Dias
The development of a new primary calibration system for laser vibrometers at INMETRO
The laser vibrometer (LV) is a powerful non-contact transducer capable of accurately measuring point motion quantities by means of interferometric techniques. According to the requirements in standard ISO/IEC 17025, measurement traceability to the International System of Units (SI) is to be established through an unbroken chain of calibrations, linking measuring and testing equipment to the national or international measurement standards. At present, standard procedures specifying how to calibrate a laser vibrometer are still an open issue. As laser vibrometers are becoming more and more a standard measurement tool for the mechanical engineer, the establishment of standards and calibration procedures becomes more urgent. Otherwise, LVs can not be used in many applications such as a reference for the calibration of accelerometers by secondary laboratories. The vibration laboratory of INMETRO has two digital laser vibrometers and is developing a new calibration system to trace them back to the Brazilian national measurement standards. Basically, two alternative methods are applicable: primary calibration by laser interferometry, and secondary calibration by comparison to a reference transducer traceable to a national standard. This paper focuses on the primary calibration of laser vibrometers against a homodyne quadrature interferometric system. The system under development may be able to calibrate LVs with both analog and digital outputs. The theory of the method is briefly described. The scheme of the new experimental setup is presented and some experimental results obtained in a preliminary implementation are given.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Wan-Sup Cheung, Sang-Myong Park
Progress in development of primary angular vibration calibration systems
The angular vibration calibration system is not well established even in most of NMI’s. Moreover, it is not certain that suppliers of angular vibration pickups have well maintained the traceability of their calibration systems, unlike the linear vibration calibration systems well established in the industrial sector. This paper points out several technical issues encountered in setting up the angular vibration calibration system in KRISS. The first was to develop a new angular vibration exciter that is not commercialized yet. The angular vibration calibration system can not do without the angular vibration generation apparatus. The multi-layered PCB manufacturing technology is exploited to make the rotating coil designed to generate the Lorenz force. The first prototype model of the angular vibration exciter built up in KRISS is illustrated in this paper. It is shown to meet the requirements of the amplitude stability, the total harmonic distortion, and the hum and noise components, recommended in Clause ISO16063-15. Furthermore, it is shown the measured frequency responses that it can generate angular vibration over the frequency range of 5 Hz to 1 kHz (or more). Main features of the angle prism based interferometer set up in KRISS are addressed. Three uncertainty components are introduced and their evaluated uncertainty contribution is demonstrated. Those results are very useful to judge the measurement capability of the angle prism based interferometer.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Akihiro Oota, Takashi Usuda, Hideaki Nozato, Tamio Ishigami, Hisayuki Aoyama, Katsuhisa Kudo
Development of primary calibration system for high frequency range up to 10 kHz
In this paper, a new primary calibration system for the frequency range from 5 kHz to 10 kHz at the National Metrology Institute of Japan (NMIJ) is reported. In the high frequency range, the displacement amplitude becomes small and the effects of parasitic motion, such as drift motion and external noise, become greater with increasing frequency. Therefore, the realization of the primary calibration system becomes difficult. The new primary calibration system for the high frequency range is implemented with a newly designed laser interferometer and a new signal processing algorithm, which is named the multiple sinusoidal approximation method. The new designed laser interferometer has a twofold optical path to detect a small displacement with high accuracy, as well as a flexible alignment mechanism for the measurement position. The multiple sinusoidal approximation method can correct the effect of parasitic motion, which leads to high accuracy acceleration measurement. As a result, the new primary calibration system has realized a calibration capability within an expanded uncertainty of 0.5%.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

T. Licht, S. E. Salboel
Primary vibration calibration by laser interferometry and mechanical shortcomings
Primary vibration calibration by laser interferometry using quadrature outputs has been used for the last 10-15 years. The ISO 16063-11 was published in 1999 and this has increased the interest further.
With new compact laser interferometers the difficulties of optical alignment and adjustment has been practically eliminated and dedicated software has made the process automatic, permitting to gather much more data.
Furthermore the advancement in electronic measurement capabilities, especially in high precision A/D converters, has made the electrical parts of the error budget very small.
Therefore today the dominating error sources are of mechanical nature. The problem that the laser beam not always can be directed towards the point or surface to which it ideally should be directed, introduces errors that can be quite significant and often will dominate the final error budget.
At low frequencies this is often due to non-ideal exciter motion, at high frequencies due to relative motion between points on apparently rigid mechanical structures. The ISO standards and other published material do not treat these problems in detail; only very general comments are given.
To help the calibration laboratories to a better understanding and agreement of uncertainties some practical examples, finite element modelling and corresponding measurements will be given. Examples of solutions to these problems including uncertainty calculations will be presented.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Mark I. Schiefer
New Techniques in Primary Accelerometer Calibration
This paper will discuss a newly developed implementation of ISO 16063 style primary accelerometer calibrations. The goal is a laser primary accelerometer calibration system capable of performing low uncertainty primary accelerometer calibrations while maintaining the throughput and simplicity of a traditional back-to-back calibration system.
Primary accelerometer calibrations typically require multiple measurement passes at several locations across the device to be calibrated by primary means. This paper discloses the novel use of a dual beam, simultaneous primary calibration laser interferometer based system. The use of dual beam and multiple pass Michelson Interferometers greatly improves not only the reliability of the measurement, but significantly simplifies the setup and measurement process of primary laser calibrations of accelerometers.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

S. Rusnáková, P. Koštial, D. Bakošová, J. Kucerova, M. Mokryšová
Experimental Study of Plates by ESPI
Fibre-reinforced components of various shapes and different boundary conditions (free, clamped, and hinged) commonly occur in practice. Designers need to be able to predict the stiffness parameters and damping values of such components for conditions such as aeroelasticity, acoustic fatigue, and so on. Electronic speckle pattern interferometry (ESPI) can be useful tool for easily determination of Poisson’s ratio, Young's modulus E and shear modulus G from the measured resonant frequencies. In this study we investigate the vibration behaviour of square composite plates with different stacking sequences by ESPI and influence of various thicknesses to resonant frequencies of corresponding mode shapes. Both resonant frequencies and corresponding mode shapes can be compared by numerical calculations by the finite element method. Good agreement is obtained for both results of resonant frequencies and mode shapes. The mode shapes of laminate composite plates are influenced by material properties, boundary conditions, geometry, and the lamination arrangement.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

P. RATTANANGKUL, B. THUMMAWUT, V. PLANGSANGMAS,A. OHTA, T. USUDA
The Bilateral Comparison for Charge Sensitivity of Standard Accelerometer between NIMT and NMIJ
The Bilateral Comparison between National Institute of Metrology (Thailand), NIMT and National Metrology Institute of Japan, (NMIJ) was conducted in order to confirm the capability of NIMT. The calibration of charge sensitivity of the accelerometer was carried by interferometry method according to ISO 16063-11. The calibration results were then compared at the frequency range of 50Hz to 5000Hz. The reference standard accelerometer Bruel & Kjaer 8305 was assigned as the artifact.
The calibration methods of NMIJ were according to the Fringe-Counting Method at the frequency range of 20 Hz – 80 Hz and Sine Approximation Method at the frequency range of 100 Hz – 5000 Hz. While the calibration methods of NIMT were according to the Fringe-Counting Method at the frequency range of 50 Hz – 800 Hz and Minimum Point Method at the frequency range of 1000 Hz - 5000 Hz.
The comparison results were agreeable which the EN value was less than 1.0 for the entire frequency range.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Gustavo P. Ripper, Guillermo Silva-Pineda
A bilateral acceleration comparison between CENAM and INMETRO
A bilateral key comparison was conducted in the area of vibration between the National Institute of Metrology, Standardization and Industrial Quality (INMETRO), Brazil and the Centro Nacional de Metrología (CENAM), in Mexico; with INMETRO acting as pilot laboratory. This comparison was registered in the BIPM key comparison database (Mutual Recognition Arrangement - Appendix B) as SIM.AUV.V-K1.1 and the measurements were carried out by the participating laboratories from October 2004 to March 2006. The aim of this exercise was to compare primary interferometric measurements of complex charge sensitivity of standard accelerometers under sinusoidal linear accelerations in the frequency range from 10 Hz to 10 kHz. In addition, it was intended to provide a link between INMETRO and the key comparison reference values (KCRVs) established in the CIPM key comparison CCAUV.V-K1. This link of the regional metrology organization (RMO) key-comparison SIM.AUV.V-K1.1 to the International Committee for Weights and Measures (CIPM) key-comparison CCAUV.VK1 can be established because CENAM participated in both comparisons. Both participants used automated calibration systems based on homodyne quadrature laser interferometers to measure the sensitivity magnitude and the phase shift of two backto- back standard accelerometers in compliance with the international standard ISO 16063-11:1999.
The results reported by the participating laboratories at 30 specified frequencies and the respective calculated degrees of equivalence are presented. These results show an agreement better than 0,3 % from 10 Hz to 5 kHz and than 1% from 6 kHz to 10 kHz in sensitivity magnitude and better than 0,6D in phase shift in the entire frequency range.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Th. Bruns, C. S.Veldman
A Web-based Data Generator for Software-Validation and Algorithm Comparison in Primary Accelerometer Calibration
During the 18th IMEKO World Congress 2006 in Rio de Janeiro the members of the TC22 discussed the options to validate and compare different algorithms used worldwide by NMIs in the field of primary accelerometer calibration. The goal would be to validate calibration results calculated with the help of reference data sets and compare the different algorithms with data sets including well defined disturbances. This would expose the susceptibility or immunity of the algorithms with respect to signal disturbances.
The challenge in such an approach is the multitude of measurement set-ups available in the NMIs and the respective diversity of parameters and data sources. In order to cope with this diversity the approach of a web-based data generator will be introduced. The aim is to provide a browser-based interface for a data synthesis software.
Details about the incorporated calibration set-ups, the considered disturbances, the mode of calculation and the internet technology used for deployment will be discussed in the presentation.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

P. Koštial, D. Bakošová, N. Krecmer, M. Mokryšová, S. Rusnáková, J. Kucerová
Experimental Modal Analysis of Tyres by ESPI
With help of the ESPI tool we have determined vibration modes of different tyres. In the paper we studied also the influence of the tyre inflation on the vibration mode dynamic. The obtained results were qualitatively compared with those obtained by application of the finite element method (FEM) in the Marc software environment.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Holger Nicklich, Martin Brucke
Latest Design of Sine and Shock Exciters for Calibration Purposes
SPEKTRA is a leading manufacturer of Calibration Systems for vibration and acoustic sensors for use in laboratory applications.
Special hardware, software and system concepts have been jointly developed for the mass production of MEMS. Since in sensor production and some metrological applications extreme requirements for sine and shock levels and frequency ranges have to be met, SPEKTRA has decided to design special exciters of their own.
The paper will present new designs, measurement results and examples of applications to calibration systems. The extended capabilities of the high frequency air bearing vibration exciter SE-09 will be discussed in more detail. Applications to primary and secondary calibration systems will be demonstrated and measurement results will be given.
For the high shock exciters of types HOP-S and HOP-P, theoretical considerations of how to scale up their shock amplitudes without compromising highest quality signal waveforms and excellent stability of mechanical excitation will be discussed and compared with practical measurement results.
Finally an outlook on further developments of vibration and shock exciters for use in calibration and sensor production will be given.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

Diana Milcic, Dubravko Banic, Davor Donevski
The effective vibration speed of web offset press
The purpose of this study was to investigate the existing maintenance models of web offset presses, and to propose the method which increases the reliability of the printing press exploitation, but does not require big investments. Doctor motors allowed constant monitoring by measuring instruments, which allowed insight in current status of motors at any time, so they could be repaired or replaced before malfunction. The effective vibration speed (v_RMS) was measured a few times during the year 2006. Standard ISO 2372-1974 (E) defines values and boundaries of the effective vibration speed (v_RMS). Results of measuring effective vibration speed indicated the emersion of nuisance energy with deterioration. To determine the state of bearings, and check if they cause the increase of effective vibration speed, an envelope analysis - FFT of the acceleration specter is conducted. This decreases the probability of motor malfunction and greatly increases the reliability of the whole system.
1st Conference on Vibration Measurement (together with 20th Conference on Measurement of Force, Mass and Torque & 3rd Conference on Pressure Measurement), Merida, MEXICO, 2007

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