A high stability optical shadow sensor with applications for precision accelerometers

Bramsiepe, S. G. , Loomes, D., Middlemiss, R. P. , Paul, D. J. and Hammond, G. D. (2018) A high stability optical shadow sensor with applications for precision accelerometers. IEEE Sensors Journal, 18(10), pp. 4108-4116. (doi:10.1109/JSEN.2018.2818066)

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Abstract

Displacement sensors are found in a variety of applications including gravitational wave detectors, precision metrology, tissue imaging, gravimeters, microscopy, and environmental monitoring. Most of these applications benefit from the use of displacement sensors that offer both high precision and stability. This is particularly the case for gravimetry where measurements are often taken over multi-day timescales. In this paper we describe a custom-built microcontroller-based displacement sensor that has been utilized in a micro-electromechanicalsystem gravimeter. The system runs off battery power and is low-cost, portable, and lightweight. Using an optical shadow sensor technique, and by designing a digital lock-in amplier based around a dsPIC33 microcontroller, we demonstrate a displacement sensitivity of 10 nm/Hz down to 300 s, and an rms sensitivity of 1 nm over timescales of one day. The system also provides real time monitoring/control of temperature, using an AD7195 ratiometric bridge to provide mK control of three separate PT100 sensors. Furthermore, a tilt sensor conditioning circuit is incorporated to drive a pair of electrolytic tilt sensors, resulting in the ability to monitor 2 axis tilt at the level of 1 microradian over approximately 1 day. The sensor system described is thus multifunctional and capable of being incorporated into precision accelerometers/gravimeters, or indeed other applications where long term displacement/temperature monitoring is necessary.

Item Type:Articles
Additional Information:This work was supported by EPSRC QuantIC under Grant EP/MO1326X/1. The work of S. G. Bramsiepe was supported by EPSRC under Grant EP/L016753/1.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Bramsiepe, Steven and Hammond, Professor Giles and Paul, Professor Douglas and Middlemiss, Dr Richard
Authors: Bramsiepe, S. G., Loomes, D., Middlemiss, R. P., Paul, D. J., and Hammond, G. D.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
College of Science and Engineering > School of Physics and Astronomy
Journal Name:IEEE Sensors Journal
Publisher:IEEE
ISSN:1530-437X
ISSN (Online):1558-1748
Published Online:21 March 2018

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
636381EPSRC Centre for Doctoral Training in Sensing and MeasurementAndrew HarveyEngineering and Physical Sciences Research Council (EPSRC)EP/L016753/1SCHOOL OF PHYSICS & ASTRONOMY