Dynamic Structure Evaluation of Isolation Seismic Block for Primary Vibration Calibration System
Yeu-Jong Huang, Chao-Jung Chen, Sheng-Hang Wang, Kuang-Yih Tsuei, Henner Baitinger, Christian Walter
Abstract:
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.
Keywords:
seismic block, experimental modal, natural frequency, vibration isolation
Download:
IMEKO-TC22-2007-108u.pdf
DOI:
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Event details
IMEKO TC:
TC22
Event name:
Cultivating metrological knowledge
Title:
1st Conference on Vibration Measurement (together with 20th TC3 Conference on Measurement of Force, Mass and Torque & 3rd TC16 Conference on Pressure Measurement)
Place:
Merida, MEXICO
Time:
27 November 2007 - 01 December 2007
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