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A fibre optic sensor for ambiguity measurement of apparent strain produced by electrical strain gauge-transient-heating-effect

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A fibre optic sensor for ambiguity measurement of apparent strain produced by electrical strain gauge-transient-heating-effect
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  See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/224146764 A Fibre Optic Sensor for Ambiguity Measurement of Apparent Strain Produced by Electrical Strain Gauge-Transient-Heating-Effect Conference Paper   in  Conference Record - IEEE Instrumentation and Measurement Technology Conference · June2010 DOI: 10.1109/IMTC.2010.5488190 · Source: IEEE Xplore CITATIONS 0 READS 18 2 authors:Some of the authors of this publication are also working on these related projects: Fiber-Optic-Based Smart Wear (FOSW) for Health Monitoring: Simulation and Optimization   ViewprojectMohamed Tarek Ibrahim El-WakadHelwan University 23   PUBLICATIONS   87   CITATIONS   SEE PROFILE Tarek ElsarnagawyPrince Sultan University 32   PUBLICATIONS   86   CITATIONS   SEE PROFILE All content following this page was uploaded by Mohamed Tarek Ibrahim El-Wakad on 30 December 2016. The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the srcinal documentand are linked to publications on ResearchGate, letting you access and read them immediately.  T h i    s  a r  t  i    c l    e i    s  p r  o  t   e  c  t   e  d  b  y  G  e r m a n  c  o  p  y r i    g h  t  l    a w.Y  o  u m a  y  c  o  p  y  a n  d  d i    s  t  r i    b  u  t   e  t  h i    s  a r  t  i    c l    e f    o r  y  o  u r  p  e r  s  o n  a l    u  s  e  o n l    y . O  t  h  e r  u  s  e i    s  o n l    y  a l   l    o w e  d wi    t  h wr i    t   t   e n  p  e r mi    s  s i    o n  b  y  t  h  e  c  o  p  y r i    g h  t  h  o l    d  e r . tm 7–8/2009   Beiträge Effect of the Embedding Techniquein Fibre-Optic-Based Force Sensorfor Dentistry: Nano-strain Analysis Faserkraftsensor im Nanodehnungsbereich für Dentalanwendungen Tarek Elsarnagawy, Mohamed-Tarek El-Wakad, King Saud University, Riyadh, Saudi Arabia Summary  The aim of this study is to evaluate the ability offibre optics in measuring nano-strains developed in dentistrydue to small chewing force. Since long fibres were used before,therefore, short fibres were evaluated in this study. In this di-rection the results from three short fibres sensors (coated withadhesive, coated without adhesive, and uncoated with adhe-sive) were collected. The results were compared to each otherand to strain values from electrical strain gauge. The results re-vealed superiority of the short fibre with adhesive among all thesensors in sensitivity and accuracy including the strain gauge.The results of the short fibre were, then, compared to resultsof previous study long fibre. Again, the accuracy of the shortfibre sensor was higher than that of the long fibre (deviationof 3% and 12% errors, respectively). In terms of sensitivity,the sensitivity of the short fibre was about 30% of the longfibre. However, sensitivities of both short and long fibres werein the nano-strain region (74 and 17 nano-stains respectively)and were much higher than electrical strain gauge (micro-strain range).  ◮◮◮  Zusammenfassung  In dieser Studiewurden kurze Längen von optischen Fasern ausgewertet, umNanodehnungen zu messen, die in der Zahnmedizin auf Grundgeringer Kaukraft entstanden. Optische Dentalfasersensoren(FODS) wurden in unterschiedlichen Konfigurationen getestet:eine ummantelte optische Faser verbunden mit dem Verfor-mungskörper, eine ummantelte optische Faser, die nicht mit ihmverbunden ist und eine nicht ummantelte optische Faser, die mitdem Körper verbunden ist. Die Ergebnisse wurden miteinanderund mit den DMS-Werten verglichen. Dies ergab eine Über-legenheit der angebrachten Kurzfaser unter allen benutztenSensoren in Bezug auf Empfindlichkeit und Genauigkeit. DieErgebnisse wurden anschließend mit den vorherigen Ergebnis-sen der Langfaser verglichen. Wieder war die Genauigkeit desKurzfasersensors höher als die der Langfaser (Abweichung von3% bzw. 12%). Hinsichtlich der Empfindlichkeit lag die derKurzfaser bei 30% der Langfaser. Jedoch lag die Empfindlichkeitder Kurzfaser wie auch der Langfaser im Nanodehnungsbe-reich (74 bzw. 17ppb) und war viel höher als bei elektrischenDehnungsmessstreifen (Mikrodehnungsbereich). Keywords  Bite force, fibre optics, strain gauge, nano-strain, sensors, dentistry  ◮◮◮  Schlagwörter  Kaukraft, Faseroptik,Dehnungsmessung, Nanodehnungsbereich, Dentalanwendung 1 Overview Chewing forces is an important parameter to measure indentistry indicator of the functional state of the masti-catory system [1]. However the available transducers are relatively large in size causing mouth to open beyondits normal occlusion. Such opening gives a false valueof the chewing force [2;3]. The most common sensor used chewing force transducers is electrical strain gauges(ESG) whose sensitivity is in the micro range. Longerfibres as a sensor for chewing force measurement wereused in a previous study  [4]. In such a study, results from fibre optics dental sensor (FODS) using laser diode 378  tm  – Technisches Messen 76 (2009) 7–8 /  DOI  10.1524/teme.2009.0975  © Oldenbourg Wissenschaftsverlag  T h i    s  a r  t  i    c l    e i    s  p r  o  t   e  c  t   e  d  b  y  G  e r m a n  c  o  p  y r i    g h  t  l    a w.Y  o  u m a  y  c  o  p  y  a n  d  d i    s  t  r i    b  u  t   e  t  h i    s  a r  t  i    c l    e f    o r  y  o  u r  p  e r  s  o n  a l    u  s  e  o n l    y . O  t  h  e r  u  s  e i    s  o n l    y  a l   l    o w e  d wi    t  h wr i    t   t   e n  p  e r mi    s  s i    o n  b  y  t  h  e  c  o  p  y r i    g h  t  h  o l    d  e r .   Effect of the Embedding Technique in Fibre-Optic-Based...  ◮◮◮ (LD) as well as a helium laser were compared to eachother as well as to electrical strain gauge (ESG). Then,the measured strains by the three sensors were comparedto expected theoretical strain values. The results of thestudy showed that fibre optics techniques are more sen-sitive than electrical strain gauges. However, the FODStechniques are less accurate than ESG. The reduced accu-racy can be referred to the inhomogeneity of the adhesivelayer [5], which is used to bond the sensing optical fibreto the deformation body, resulting from the long lengthof the fibre. Such inhomogeneities are expected to causesome variation in the intrinsic characteristics of the fibre(e.g. micro-bending). This in turn leads to degradationin accuracy of the adhered fibre optics sensor. The strainresults when using shorter wavelength source (HeNe) im-proved the accuracy slightly. Furthermore, it showed thecapability of fibre optics to measure strains in the nano-range; as low as 17 nano-strain value. In order to reducethe effect of the inhomogeneous layer arising with longfibre a shorter fibre is recommended to be used. Since thegoal of both studies is to develop a technique to apply indentistry the use of short fibre seems practical in orderto miniaturize the sensors. 2 Material and Method The experimental setup used in this experiment wasthe same as the one used in a previous study  [4]. As mentioned before, the errors were attributed to thelack of homogeneity in the adhesive layer when usinglong lengths of the sensing fibre. Therefore the core of this research is to investigate the effect of changing thefibre length. The fibre used in this study was a SM800-FIBRECORE LTD of length 0.9 m. In order to investigatethe effects of adhesive and coating the fibre was tested onthe transducer in the following combinations: •  Coated fibre with adhesive applied to the whole length. •  Coated fibre with adhesive at both ends only to inves-tigate the effect of adhesive absence •  Uncoated fibre with adhesive applied to the wholelength to investigate the effect of the coating absence.Data were collected from the three trials and comparedto each other. It was, then, compared to the data froman electrical strain gauge (ESG). 3 Results and Discussion The goal of this study is to evaluate the effect of shortFODS as a way to improve the accuracy of a previously tested technique using long FODS. As mentioned before,the reduced accuracy can be referred to the inhomoge-neous layer of the adhesive that may cause micro-bendingwhich reduces accuracy. Literature points out that usinga secondary coating sensitive to characteristics of theparameter to be measured can improve accuracy andsensitivity [6]. If the FODS is bonded to a hollow man-drel, the mandrel act to amplify induced optical pathlength difference due to the externally applied pressure(or force). Therefore, the FODS was bonded to a cylinderrepresenting a dental implant, then, a secondary coatingwas applied.At the beginning the resultant counts of the FODSduring the calibration procedure involving the three com-binations of the short FODS are shown in Table 1 andplotted in Fig. 1.In Fig. 1, sensitivity of sensors is compared by numberof counts measured at an applied load. Figure 1 showsthat the sensitivity of the adhesive/coat case exceededthose of adhesive/no-coat and no-adhesive/coat values.Quantitatively the sensitivity of the former is 2.7 and 5.4times of the other two combinations, respectively.The resultant counts of all FODS combinations wereexpressed into its corresponding strain values. These re-sults along with the ESG results are shown in Table 2and plotted in Fig. 2. The figure shows that sensitivity  of the measurements from adhesive/coat and from theESG sensors were close to each other. Furthermore, itindicates a much higher sensitivity than the other twocombinations.Looking at the accuracy, results were compared versustheoretical strain values as shown in Table 3 and displayedin Fig. 3.It is commonly known that slope values closer to 1 in-dicate high accuracy. Thus Fig. 3 shows that the slopes of  Table1  Load versus counts for all 3 FODS.Load Counts(KN) Adhesive/ No-adhesive/ Adhesive/coat coat no-coat0 0 0 010 500 183 7520 1000 354 16030 1450 526 25040 1900 755 34050 2350 860 43560 2900 1050 52570 3350 1250 62080 3800 1400 71090 4300 1600 800100 4750 1750 890 Figure1  Load versus counts from all FODS combinations during cali-bration. 379  T h i    s  a r  t  i    c l    e i    s  p r  o  t   e  c  t   e  d  b  y  G  e r m a n  c  o  p  y r i    g h  t  l    a w.Y  o  u m a  y  c  o  p  y  a n  d  d i    s  t  r i    b  u  t   e  t  h i    s  a r  t  i    c l    e f    o r  y  o  u r  p  e r  s  o n  a l    u  s  e  o n l    y . O  t  h  e r  u  s  e i    s  o n l    y  a l   l    o w e  d wi    t  h wr i    t   t   e n  p  e r mi    s  s i    o n  b  y  t  h  e  c  o  p  y r i    g h  t  h  o l    d  e r .   Beiträge Table2  Load versus measured strains for 3 FODS.StrainLoadAdhesive/ No-adhesive/ Adhesive/ ESG(KN)coat coat no-coat0 0 0 0 010 5.01 × 10 –5 1.83 × 10 –5 7.51 × 10 –6 4.20 × 10 –5 20 1.00 × 10 –4 3.55 × 10 –5 1.60 × 10 –5 8.00 × 10 –5 30 1.45 × 10 –4 5.27 × 10 –5 2.50 × 10 –5 1.26 × 10 –4 40 1.90 × 10 –4 7.56 × 10 –5 3.41 × 10 –5 1.67 × 10 –4 50 2.35 × 10 –4 8.61 × 10 –5 4.36 × 10 –5 2.09 × 10 –4 60 2.90 × 10 –4 1.05 × 10 –4 5.26 × 10 –5 2.51 × 10 –4 70 3.36 × 10 –4 1.25 × 10 –4 6.21 × 10 –5 2.93 × 10 –4 80 3.81 × 10 –4 1.40 × 10 –4 7.11 × 10 –5 3.34 × 10 –4 90 4.31 × 10 –4 1.60 × 10 –4 8.01 × 10 –5 3.76 × 10 –4 100 4.76 × 10 –4 1.75 × 10 –4 8.91 × 10 –5 4.18 × 10 –4 Figure2  Measured strain from all sensors during calibration process. Table3  Theoretical versus measured strains.Theoretical Adhesive/ No-adhesive/ Adhesive/ ESGStrain coat coat no-coat0 0 0 0 04.52 × 10 –5 5.01 × 10 –5 1.83 × 10 –5 7.51 × 10 –6 4.20 × 10 –5 9.00 × 10 –5 1.00 × 10 –4 3.55 × 10 –5 1.60 × 10 –5 8.00 × 10 –5 1.36 × 10 –4 1.45 × 10 –4 5.27 × 10 –5 2.50 × 10 –5 1.26 × 10 –4 1.81 × 10 –4 1.90 × 10 –4 7.56 × 10 –5 3.41 × 10 –5 1.67 × 10 –4 2.26 × 10 –4 2.35 × 10 –4 8.61 × 10 –5 4.36 × 10 –5 2.09 × 10 –4 2.71 × 10 –4 2.90 × 10 –4 1.05 × 10 –4 5.26 × 10 –5 2.51 × 10 –4 3.16 × 10 –4 3.36 × 10 –4 1.25 × 10 –4 6.21 × 10 –5 2.93 × 10 –4 3.62 × 10 –4 3.81 × 10 –4 1.40 × 10 –4 7.11 × 10 –5 3.34 × 10 –4 4.07 × 10 –4 4.31 × 10 –4 1.60 × 10 –4 8.01 × 10 –5 3.76 × 10 –4 4.52 × 10 –4 4.76 × 10 –4 1.75 × 10 –4 8.91 × 10 –5 4.18 × 10 –4 Figure3  Theoretical strain vs. measured strain. Figure4  Strain: Theoretical vs. Long & Short FODS. both ESG and the FODS (adhesive/coating-combination)are 0.9265 and 1.05, respectively. This indicates that bothhave highest accuracy among the four used sensor com-binations. Such slopes are equivalent to angles of about42.8 and 46.4 degrees, respectively. These angles indicatea deviation of about 5 % and 3.1 % , respectively, from thetheoretical expected values. Furthermore, it can be seenthat FODS (adhesive/coat) is more accurate than the ESG.On the other hand, the accuracy of the other two FODScases (no adhesive/with coating and adhesive/withoutcoating) are far from theoretical. Their slopes of 0.39 and0.20 are equivalent to 21.2 and 11.3 degrees, respectively.Such angles indicate deviations of 52.2 % and 74.8 % , re-spectively, from theoretical expected strain values. Suchresults make it clear that although the adhesive layer andthe fibre coating may introducesome error, yet, it is muchsmaller than the errors that appear when excluding eitherthe coating or the adhesive. The high sensitivity of formercombinations can be attributed to the fact that the coat-ing and adhesive introduce an augment of the effect of the applied force on the fibre. Such augmentation of theforce results in more counts and consequently increasessensitivity of the sensor [3]. In addition, coating/adhesive combination represents a perfect embedding for the fibrewhich decreases errors in transmitting the effect of theacting force on the fibre in addition to a tight embed-ding of the fibre, thus, increasing accuracy. Moreover,the large deviation between bonded coated vs. uncoatedfibre can be explained as that the compatibility of theinterface between the polymeric adhesive material andthe polymeric coating is much better than that betweenadhesive material and glass fibre. Thus, the coating layeris more intact in the former case compared to the laterone.The main goal of this study is to investigate the ca-pabilities of short fibre length. Since the setup used withlong FODS is the same as the one used with short FODSthe results of both studies were compared. This com-parison is shown in Fig. 4. The figure shows that using a long FODS yields a deviation of about 12 %  from thetheoretical strain value. On the other hand, the use of the short FODS yields a deviation of about 3 % only fromthe theoretical strain value. This could be explained by a reduction in the errors arising from the inhomogeneous 380  T h i    s  a r  t  i    c l    e i    s  p r  o  t   e  c  t   e  d  b  y  G  e r m a n  c  o  p  y r i    g h  t  l    a w.Y  o  u m a  y  c  o  p  y  a n  d  d i    s  t  r i    b  u  t   e  t  h i    s  a r  t  i    c l    e f    o r  y  o  u r  p  e r  s  o n  a l    u  s  e  o n l    y . O  t  h  e r  u  s  e i    s  o n l    y  a l   l    o w e  d wi    t  h wr i    t   t   e n  p  e r mi    s  s i    o n  b  y  t  h  e  c  o  p  y r i    g h  t  h  o l    d  e r .   Effect of the Embedding Technique in Fibre-Optic-Based...  ◭◭◭ adhesive layer in the case of short FODS. It is worth men-tioning that the “sandwich” effect of adhesive layers onboth long and short fibre causes transversal force whichproduces an increase in photoelastic effects of the fibre.This means a decrease in sensitivity since it opposes themeasured effect which is strain in our case [6;7]. How- ever, comparing sensitivity of both lengths showed thatfor long FODS it is much higher than that of the shortFODS. This is indicated by comparing the resultant num-ber of counts measured from both FODSs under the sameload. Such comparison showed that under a 100kN loadthe number of counts of 4750 in the case of short FODSvs. 16250 in the case of long FODS. This means that thesensitivity of the short FODS is about 30 %  of that of the long FODS. However, it is still in the nano range (1count is equivalent to about 78 nano-strains in the shortFODS compared to 17 nano-strains in the long fibre).But this insignificant loss in sensitivity is compensated by an increase in accuracy of the short FODS of about 60 % . 4 Conclusions The purpose of this study was to investigate the effectof the FODS length, adhesive and FODS coating on theaccuracy of a proposed system for a FODS-based sensorfor dental applications. Within the limits of this study,the following can be concluded:1. Short FODS provides the best accurate system amongthose tested in this study (deviation of about 3 % ).2. Short FODS is less sensitive than Long FODS by about70 % .3. Sensitivity in both FODS lengths is still in the nanorange and much more than that of the ESG withcommonly available strain meters in the micro-strainrange.4. Excluding the adhesive or the coating yields very largedeviations in the measurements (52.2 %  and 74.8 % ,respectively). References [1] Bakke, M.: Bite force and occlusion. Semin Orthod  12 , 120–126(2006).[2] Kleinfelder, J.W., Ludwigt, K.: Maximal bite force in patients withreduced periodontal tissue support with and without splinting.J. Periodontol.  73 (10), 1184–1187 (2002).[3] Fields, H.W., Proffit, W.R.: Variables affecting measurements of vertical occlusal force. J. Dent. Res.  65 (2), 135–138 (1986).[4] Elsarnagawy, T., El-Wakad, M.T.: Investigating the Prospective useof Fibre Optics Based Sensors in Dentistry, tm – TechnischesMessen  75 (3), 207–211 (2008).[5] Udd, E.: “Fibre optic sensors for infrastructure application, Finalreport” SRR 374, Research, Oregon dept. of transportation, 1998.[6] Fürstenau, N., Schmid, W., Goetting, H.-C.: “Simultaneous Inter-ferometric and Polarimetric Strain Measurements on Compositesusing a Fibre-Optic Strain Gauge”, Applied Optics  31 (16), 2987–2993 (1992).[7] Krath, K.-J.: “Glasinterferometer zur optischen Spektralanalyse”,Fortschritt-Berichte, VDI 21, Nr. 86, 1991.Received: February 18, 2009, accepted: March 4, 2009 Tarek D. Elsarnagawy   (Assist. Professor Dr. Eng.) is Chairman at theApplied Medical Sciences Department.Address: Community College King Saud University, P.O.B. 28095,11437 Riyadh, Kingdom of Saudi Arabia, e-mail: tarek99@web.de Mohamed-Tarek I. El-Wakad  (Associate Professor, Biomechanics).Address: Biomedical Technology Dept., College of Applied Medical Sci-ences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Ara-bia, e-mail: mtwakad@yahoo.com 381 View publication statsView publication stats
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