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Page 820 of 936 Results 8191 - 8200 of 9356

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.

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).

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.

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.

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.

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%.

Park Yon-Kyu, K. Min-Seok, K. Jong-Ho, C. Jae-Hyuk, K. Dae-Im
Establishment of torque standards in KRISS of Korea

Korea Research Institute of Standards and Science(KRISS) has developed a 100 N·m and a 2 kN·m deadweight torque standard machines. The 100 N·m torque machine can generate torque from 0.1 N·m to 110 N·m. The length of its torque arm is 0.25 m for both sides. It uses continuous deadweight stack. At each side, it has three different deadweight stacks. By rotating the base plate on which the deadweight stacks are located, the machine can adjust a suitable deadweight stack of appropriate torque range. Its relative uncertainty is 5 × 10-4 from 0.1 N·m to 1 N·m and 5 × 10-5 from 1 N·m to 110 N·m. The 2 kN·m deadweight torque machine uses a continuous deadweight stack at the left side and a binary type combination deadweight stack at the right side. By combining both deadweight stacks, the machine can generate torque from 10 N·m to 2200 N·m for both clockwise and counter-clockwise directions. The machine fixes its torque arm when changing the torque to maintain previous torque level. Its relative expanded uncertainty is 5 × 10-5.

D. Röske
The New version of the German torque calibration standard DIN 51309:2005-12 a comparative overview

In December 2005, the new version of the DIN 51309 was issued by DIN, the German Institute for Standardization. This standard takes into account some fundamental ideas about the target application of a torque transducer, for example high-level inter-comparison measurements or measurements in industrial environments. Two cases are considered and two different calibration results are calculated on the basis of a standard calibration procedure. For some intercomparisons, the hysteresis of the transducer does not have any influence on the result and is therefore excluded. This paper shows, on the one hand, the new version in comparison with other standards (e. g. EA-10/14) and some guidelines of the DKD, the German Calibration Service, and describes, on the other hand, its application to torque reference machines.

S. Kuhn
Advantage of carrier frecquency in contactles high precision torque measurement systems

This paper describes the advantage of carrier frequency amplifiers in rotating torque flanges. It gives an overview of the systematic effects and random errors which disturb the torque measurement and shows how the measurement errors can be suppressed by means of carrier frequency technology. The resulting high reproducibility and linearity of the new torque flange with digital signal processing and transmission is shown in torque and temperature plots.

K. Ohgushi, A. Nishino, T. OTA, K. Ueda
Expansion of the calibration range and improvement of the uncertainty in the 1 kN·m deadweight torque standard machine

Expansion of the calibration range and improvement of the uncertainty of realized torque in the 1 kN·m deadweight torque standard machine were investigated. The lower limit of the calibration range was lowered from 5 N·m to 0.5 N·m by developing new small linkage weight series. In addition, the sensitivity limit at the fulcrum was reevaluated. The moment-arm length was also re-measured after changing the thin metal bands at the ends of the moment-arm. As a result of these evaluations, relative expanded uncertainties (k = 2) of 7.3 × 10-5 and 2.9 × 10-5 could be obtained in the range from 0.5 N·m to 20 N·m and from 5 N·m to 1 kN·m, respectively.

Page 820 of 936 Results 8191 - 8200 of 9356