A laser position sensing system for the study of accelerometer rocking motion due to cable strain

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Proceedings title18th International Congress on Sound and Vibration 2011, ICSV 2011
Conference18th International Congress on Sound and Vibration 2011, ICSV 2011, 10 July 2011 through 14 July 2011, Rio de Janeiro
Pages25012508; # of pages: 8
SubjectAir bearing; Axial motions; Beam deviation; Charge amplifiers; Different mass; Electrical connectors; Lateral-Effect; Low noise; Measurement uncertainty; Mechanical dimensions; Output signal; Piezo-electric accelerometers; Position sensing system; Position-Sensitive Detectors; Real time; Reflected laser; Rocking motion; Self-generated noise; Signal paths; Solid steel; Stationary components; Two-channel; Waveform recorder; Accelerometers; Acoustic noise; Bearings (machine parts); Electric connectors; Laser beams; Lasers; Mirrors; Sensors; Uncertainty analysis; Waveform analysis; Cables
AbstractAccelerometer cables should be securely fastened to stationary components with clamp, tape, or other adhesive means to minimize relative cable motion (cable whip). Cable motion can introduce self noise, especially in high-impedance signal paths (for example, from piezoelectric accelerometer output to charge amplifier input). This self-generated noise is referred to as the triboelectric effect. Although the low-noise treatment of cable is a solution to minimizing this effect it is still necessary to limit the motion of cables to further reduce noise. When an accelerometer cable is fastened to non-moving structure it introduces cable strain near the electrical connector of the accelerometer that pushes or pulls the accelerometer while it is in movement. Such a push or pull contributes to the accelerometer rocking motion that is a main source of measurement uncertainty. In practice, leaving enough slack to allow free movement of the accelerometer while securing the cable may reduce the cable strain in trade with cable motion limitation. This paper presents the development of a laser position sensing system to study this trade-off. Dummy accelerometers are fabricated that integrate mirrors and electrical connector. The dummy accelerometers have the same mechanical dimensions of commercial accelerometers and are made of solid steel to eliminate the rocking motion due to accelerometer housing. A laser beam is incident on one of the mirrors of the dummy accelerometer. The reflected laser beam is received by a lateral effect position sensitive detector (PSD) to monitor any motion that deviates from the axial motion due to the rocking motion. A twochannel waveform recorder is used to capture the PSD output signals. The waveform recorder, which is equipped with a computer interface, is capable of analog-to-digital conversion, storage of the PSD output signals and display of laser beam deviations in real time. With this system the adjustment of cable fastening can be done in real time. An example is given in this paper that shows the accelerometer rocking motion for different cable fastening conditions. The system can also be used to study the rocking motion of a vibration shaker while performing calibration for different mass loads and air bearing flow rates. Copyright © (2011) by the International Institute of Acoustics & Vibration.
Publication date
AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for National Measurement Standards (INMS-IENM)
Peer reviewedYes
NPARC number21271252
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Record identifiera4190748-f5a9-4b81-8b3c-0577955b2a7c
Record created2014-03-24
Record modified2016-05-09
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