Simple force balance accelerometer/seismometer based on a tuning fork displacement sensor
Abstract
Seismometers and microelectromechanical system accelerometers use the force-balance principle to obtain measurements. In these instruments the displacement of a mass object by an unknown force is sensed using a very high-resolution displacement sensor. The position of the object is then stabilized by applying an equal and opposite force to it. The magnitude of the stabilizing force is easily measured, and is assumed to be equivalent to the unknown force. These systems are critically dependent on the displacement sensor. In this article we use a resonant quartz tuning fork as the sensor. The tuning fork is operated so that its oscillation is lightly damped by the proximity of the movable mass object. Changes in the position of the mass object cause changes in the phase of the fork's resonance; this is used as the feedback variable in controlling the mass position. We have developed an acceleration sensor using this principle. The mass object is a piezoelectric bimorph diaphragm which is anchored around its perimeter, allowing direct electronic control of the displacement of its center. The tuning fork is brought very close to the diaphragm center, and is connected into a self-oscillating feedback circuit which has phase and amplitude as outputs. Themore »
- Authors:
-
- Department of Electrical Engineering, University of Cape Town, Rondebosch 7701 (South Africa)
- Publication Date:
- OSTI Identifier:
- 20643978
- Resource Type:
- Journal Article
- Journal Name:
- Review of Scientific Instruments
- Additional Journal Information:
- Journal Volume: 75; Journal Issue: 9; Other Information: DOI: 10.1063/1.1786333; (c) 2004 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ACCELERATION; ACCELEROMETERS; AMPLITUDES; BALANCES; OSCILLATIONS; PIEZOELECTRICITY; QUARTZ; SEISMIC DETECTION; SEISMIC NOISE; SENSITIVITY; TUNING
Citation Formats
Stuart-Watson, D, and Tapson, J. Simple force balance accelerometer/seismometer based on a tuning fork displacement sensor. United States: N. p., 2004.
Web. doi:10.1063/1.1786333.
Stuart-Watson, D, & Tapson, J. Simple force balance accelerometer/seismometer based on a tuning fork displacement sensor. United States. https://doi.org/10.1063/1.1786333
Stuart-Watson, D, and Tapson, J. 2004.
"Simple force balance accelerometer/seismometer based on a tuning fork displacement sensor". United States. https://doi.org/10.1063/1.1786333.
@article{osti_20643978,
title = {Simple force balance accelerometer/seismometer based on a tuning fork displacement sensor},
author = {Stuart-Watson, D and Tapson, J},
abstractNote = {Seismometers and microelectromechanical system accelerometers use the force-balance principle to obtain measurements. In these instruments the displacement of a mass object by an unknown force is sensed using a very high-resolution displacement sensor. The position of the object is then stabilized by applying an equal and opposite force to it. The magnitude of the stabilizing force is easily measured, and is assumed to be equivalent to the unknown force. These systems are critically dependent on the displacement sensor. In this article we use a resonant quartz tuning fork as the sensor. The tuning fork is operated so that its oscillation is lightly damped by the proximity of the movable mass object. Changes in the position of the mass object cause changes in the phase of the fork's resonance; this is used as the feedback variable in controlling the mass position. We have developed an acceleration sensor using this principle. The mass object is a piezoelectric bimorph diaphragm which is anchored around its perimeter, allowing direct electronic control of the displacement of its center. The tuning fork is brought very close to the diaphragm center, and is connected into a self-oscillating feedback circuit which has phase and amplitude as outputs. The diaphragm position is adjusted by a feedback loop, using phase as the feedback variable, to keep it in a constant position with respect to the tuning fork. The measured noise for this sensor is approximately 10.0 mg in a bandwidth of 100 Hz, which is substantially better than commercial systems of equivalent cost and size.},
doi = {10.1063/1.1786333},
url = {https://www.osti.gov/biblio/20643978},
journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 9,
volume = 75,
place = {United States},
year = {Wed Sep 01 00:00:00 EDT 2004},
month = {Wed Sep 01 00:00:00 EDT 2004}
}