0 Hz AND LOW FREQUENCY CALIBRATION OF LOW FREQUENCY REFERENCE ACCELEROMETERS |
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| Torben R. Licht, Sven Erik Salboel |
- Abstract:
- 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. - Keywords:
- vibration, calibration, gravity, interferometry
- Download:
- IMEKO-TC22-2014-014.pdf
- DOI:
- -
- Event details
- IMEKO TC:
- TC22
- Event name:
- TC22 Conference 2014
- Title:
3rd Conference on Vibration Measurement (together with 22nd TC3 Conference on the Measurement of Force, Mass and Torque and 12th TC5 Conference on the Measurement of Hardness)
- Place:
- Cape Town, SOUTH AFRICA
- Time:
- 03 February 2014 - 06 February 2014