<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "https://jats.nlm.nih.gov/nlm-dtd/publishing/3.0/journalpublishing3.dtd">
<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="3.0" xml:lang="en">
<front>
<journal-meta>
<journal-id journal-id-type="publisher">JSSS</journal-id>
<journal-title-group>
<journal-title>Journal of Sensors and Sensor Systems</journal-title>
<abbrev-journal-title abbrev-type="publisher">JSSS</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">J. Sens. Sens. Syst.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">2194-878X</issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/jsss-2-103-2013</article-id>
<title-group>
<article-title>Ultrasound-based density determination via buffer rod techniques: a review</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hoche</surname>
<given-names>S.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hussein</surname>
<given-names>M. A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Becker</surname>
<given-names>T.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Chair of Brewing and Beverage, Bio-PAT (Bio-Process Analysis Technology), Freising, Germany</addr-line>
</aff>
<pub-date pub-type="epub">
<day>31</day>
<month>07</month>
<year>2013</year>
</pub-date>
<volume>2</volume>
<issue>2</issue>
<fpage>103</fpage>
<lpage>125</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2013 S. Hoche et al.</copyright-statement>
<copyright-year>2013</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/3.0/">https://creativecommons.org/licenses/by/3.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://jsss.copernicus.org/articles/2/103/2013/jsss-2-103-2013.html">This article is available from https://jsss.copernicus.org/articles/2/103/2013/jsss-2-103-2013.html</self-uri>
<self-uri xlink:href="https://jsss.copernicus.org/articles/2/103/2013/jsss-2-103-2013.pdf">The full text article is available as a PDF file from https://jsss.copernicus.org/articles/2/103/2013/jsss-2-103-2013.pdf</self-uri>
<abstract>
<p>The review presents the fundamental ideas, assumptions and methods of
non-invasive density measurements via ultrasound at solid–liquid interface.
Since the first investigations in the 1970s there has been steady progress
with regard to both the technological and methodical aspects. In
particular, the technology in electronics has reached such a high level that
industrial applications come within reach. In contrast, the accuracies have
increased slowly from 1–2% to 0.15% for constant temperatures and to 0.4%
for dynamic temperature changes. The actual work reviews all methodical
aspects, and highlights the lack of clarity in major parts of the measurement
principle: simplifications in the physical basics, signal generation and
signal processing. With respect to process application the accuracy of the
temperature measurement and the presence of temperature gradients have been
identified as a major source of uncertainty. In terms of analytics the main source
of uncertainty is the reflection coefficient, and as a consequence of this, the amplitude accuracy in time or frequency domain.</p>
</abstract>
<counts><page-count count="23"/></counts>
</article-meta>
</front>
<body/>
<back>
<ref-list>
<title>References</title>
<ref id="ref1">
<label>1</label><mixed-citation publication-type="other" xlink:type="simple">Adamowski, J. C., Buiochi, C., Simon, C., Silva, E. C. N., and Sigelmann, R. A.: Ultrasonic measurement of density of liquids, J. Acoust. Soc. Am., 97, 354–361, 1995.</mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple">Adamowski, J. C., Buiochi, C., and Sigelmann, R. A.: Ultrasonic Measurement of Density of Liquids Flowing in Tubes, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 45, 48–56, 1998.</mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple">Asher, R. C.: Ultrasonics in chemical analysis, Ultrasonics, 25 17–19, 1987.</mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple">Bamberger, J. A. and Greenwood, M. S.: Measuring fluid and slurry density and solids concentration non-invasively, Ultrasonics, 42, 563–567, 2004a.</mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple">Bamberger, J. A. and Greenwood, M. S.: Non-invasive characterization of fluid foodstuffs based on ultrasonic measurements, Food Res. Int., 37, 621–625, 2004b.</mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple">Bjørndal, E. and Frøysa, K. E.: Acoustic Methods for Obtaining the Pressure Reflection Coefficient from a Buffer Rod Based Measurement Cell, IEEE Trans UFFC, 55, 1781–1793, 2008.</mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple">Bjørndal, E., Frøysa, K. E., and Engeseth, S. A.: A Novel Approach to Acoustic Liquid Density Measurements Using a Buffer Rod Based Measuring Cell, IEEE Trans UFFC, 55, 1794–1808, 2008.</mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple">Bolotnikov, M. F., Neruchev, Y. A., Melikhov, Y. F., Verveyko, V. N., and Verveyko, M. V.: Temperature Dependence of the Speed of Sound, Densities, and Isentropic Compressibilities of Hexane + Hexadecane in the Range of (293.15 to 373.15) K, J. Chem. Eng. Data 50, 1095–1098, 2005.</mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple">Carlson, J. E., Deventer, J., and Micella, M.: Accurate temperature estimation in ultrasonic pulse-echo systems, World Congress on Ultrasonics, Paris, 2003a.</mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple">Carlson, J. E., Deventer, J., Scolan, A., and Carlander, C.: Frequency and Temperature Dependence of Acoustic Properties of Polymers Used in Pulse-Echo Systems, IEEE ULTRASONICS SYMPOSIUM, 8030032, 885–888, 2003b.</mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple">Carstensen, E. L. and Foldy, L. L.: Propagation of Sound Through a Liquid Containing Bubbles, J. Acoust. Soc. Am., 19, 481–501, 1947.</mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple">Childs, P. R. N., Greenwood, J. R., and Long, C. A.: Review of temperature measurement, Rev. Sci. Instrum., 71, 2959–2978, &lt;a href=&quot;http://dx.doi.org/10.1063/1.1305516&quot;&gt;https://doi.org/10.1063/1.1305516&lt;/a&gt;, 2000.</mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple">Daridon, J. L., Lagourette, B., Xan, B., and Montel, F.: Petroleum characterization from ultrasonic measurement, J. Petrol. Sci. Eng., 19 281–293, 1998a.</mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple">Daridon, J. L., Lagrabette, A., and Lagourette, B.: Speed of sound, density, and compressibilities of heavy synthetic cuts from ultrasonic measurements under pressure, J. Chem. Thermodynam., 30, 607–623, 1998b.</mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple">Davis, L. A. and Gordon, R. B.: Compression of Mercury at High Pressure, J. Chem. Phys., 46, 2650–2660, 1967.</mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple">Deventer, J.: Detection of, and compensation for error inducing thin layer deposits on an ultrasonic densitometer for liquids, Instrumentation and Measurement Technology Conference 2003, 648–651, 2003.</mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple">Deventer, J.: One dimensional modeling of a step-down ultrasonic densitometer for liquids, Ultrasonics, 42, 309–314, 2004.</mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple">Deventer, J. and Delsing, J.: An Ultrasonic Density Probe, IEEE ULTRASONICS SYMPOSIUM, 1997.</mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple">Deventer, J. and Delsing, J.: Thermostatic and Dynamic Performance of an Ultrasonic Density Probe, IEEE Trans UFFC, 48, 675–682, 2001a.</mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple">Deventer, J. and Delsing, J.: Thermostatic and Dynamic Performance of an Ultrasonic Density Probe, IEEE Trans. UFFC, 48, 675–682, 2001b.</mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple">Esperança, J. M. S. S., Visak, Z. P., Plechkova, N. V., Seddon, K. R., Guedes, H. J. R., and Rebelo, L. P. N.: Density, Speed of Sound, and Derived Thermodynamic Properties of Ionic Liquids over an Extended Pressure Range. 4. [C3mim][NTf2] and [C5mim][NTf2], J. Chem. Eng. Data, 51, 2009–2015, 2006.</mixed-citation>
</ref>
<ref id="ref22">
<label>22</label><mixed-citation publication-type="other" xlink:type="simple">Fisher, B., Magpori, V., and von Jena, A.: Ultraschall (US)-Dichtemesser mm Messen der spezifischen Dichte eines Fluid, EP 0 483 491 81, Europe, 1995.</mixed-citation>
</ref>
<ref id="ref23">
<label>23</label><mixed-citation publication-type="other" xlink:type="simple">Fox, F. E., Curley, S. R., and Larson, G. S.: Phase Velocity and Absorption Measurements in Water Containing Air Bubbles, The J. Acoust. Soc. Am., 27, 534–539, 1995.</mixed-citation>
</ref>
<ref id="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple">Greenwood, M. S.: Ultrasonic fluid densitometer having liquid/wedge and gas/wedge interfaces, 6, 082, 181, United States, 2000.</mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple">Greenwood, M. S. and Bamberger, J. A.: Ultrasonic sensor to measure the density of a liquid or slurry during pipeline transport, Ultrasonics, 40, 413–417, 2002.</mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple">Greenwood, M. S. and Bamberger, J. A.: Self-Calibrating Sensor for Measuring Density Through Stainless Steel Pipeline Wall, J. Fluid. Eng., 126, 189–192, 2004.</mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple">Greenwood, M. S., Skorpik, J. R., Bamberger, J. A., and Harris, R. V.: On-line Ultrasonic Density Sensor for Process Control of Liquids and Slurries, Ultrasonics, 37, 159–171, 1999.</mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple">Greenwood, M. S., Adamson, J. D., and Bamberger, J. A.: Long-path measurements of ultrasonic attenuation and velocity for very dilute slurries and liquids and detection of contaminates, Ultrasonics, 44, e461–e466, 2006.</mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple">Guilbert, A. R. and Sanderson, M. L.: A novel ultrasonic mass flowmeter for liquids, IEE colloquium on: Advances in Sensors for Fluid Flow Measurement, London, 1996.</mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple">Hale, J. M.: Ultrasonic density measurement for process control, Ultrasonics, 26, 356–357, 1988.</mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple">Hammond, L. D. and Benjaminson, A.: The Linear Quartz Thermometer - a New Tool for Measuring Absolute and Difference Temperatures, Hewlett-Packard Journal, 16, 1965.</mixed-citation>
</ref>
<ref id="ref32">
<label>32</label><mixed-citation publication-type="other" xlink:type="simple">Henning, B., Prange, S., Dierks, K., Daur, C., and Hauptmann, P.: In-line concentration measurement in complex liquids using ultrasonic sensors, Ultrasonics, 38, 799–803, 2000.</mixed-citation>
</ref>
<ref id="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple">Higuti, R. T. and Adamowski, J. C.: Ultrasonic Densitometer Using a Multiple Reflection Technique, IEEE Trans UFFC, 49, 1260–1268, 2002a.</mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple">Higuti, R. T. and Adamowski, J. C.: Ultrasonic densitometer using a multiple reflection technique, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., 49, 1260–1268, 2002b.</mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple">Higuti, R. T., Montero de Espinosa, F. R., and Adamowski, J. C.: Energy method to calculate the density of liquids using ultrasonic reflection techniques, Proc. IEEE Ultrason. Symp., 319–322, 2001.</mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple">Higuti, R. T., Buiochi, C., Adamowski, J. C., and Espinosa, F. M.: Ultrasonic density measurement cell design and simulation of non-ideal effects, Ultrasonics, 44, 302–309, 2006.</mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple">Higuti, R. T., Galindo, B. S., Kitano, C., Buiochi, C., and Adamowski, J. C.: Thermal Characterization of an Ultrasonic Density-Measurement Cell, IEEE Transactions on Instrumentation and Measurement, 56, 924–930, 2007.</mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple">Hoche, S., Hussein, W. B., Hussein, M. A., and Becker, T.: Time-of-f light prediction for fermentation process monitoring, Eng. Life Sci., 11, 1–12, 2011.</mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple">Hoppe, N., Schönfelder, G., Püttmer, A., and Hauptmann, P.: Ultrasonic density sensor – Higher accuracy by minimizing error influences, Proc. IEEE Ultrason. Symp., 361–364, 2001.</mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple">Hoppe, N., Schönfelder, G., and Hauptmann, P.: Ultraschall-Dichtesensor für Flüssigkeiten – Eigenschaften und Grenzen, Technisches Messen, 3, 131–137, 2002.</mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple">Hoppe, N., Püttmer, A., and Hauptmann, P.: Optimization of Buffer Rod Geometry for Ultrasonic Sensors with Reference Path, IEEE Trans UFFC, 50, 170–178, 2003.</mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple">Jensen, B. R.: Measuring equipment for acoustic determination of the specific gravity of liquids, 4, 297, 608, United States, 1981.</mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple">Kaatze, U., Eggers, F., and Lautscham, K.: Ultrasonic velocity measurements in liquids with high resolution – techniques, selected applications and perspectives, Meas. Sci. Technol., 19, 1–21, &lt;a href=&quot;http://dx.doi.org/10.1088/0957-0233/19/6/062001&quot;&gt;https://doi.org/10.1088/0957-0233/19/6/062001&lt;/a&gt;, 2008.</mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple">Kaduchak, G. and Sinha, D. N.: Apparatus and method for remote, noninvasive characterization of structures and fluids inside containers, 8, 186, 004 B1, United States, 2001.</mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple">Kell, G. S.: Density, Thermal Expansivity, and Compressibility of Liquid Water from 0° to 150 °C: Correlations and Tables for Atmospheric Pressure and Saturation Reviewed and Expressed on 1968 Temperature Scale, J. Chem. Eng. Data, 20, 97–105, 1975.</mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple">Kim, J. O. and Bau, H. H.: Instrument for simultaneous measurement of density and viscosity, Rev. Sci. Instrum., 60, 1111–1115, 1989.</mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple">Krautkramer, J. and Krautkramer, H.: Ultrasonic Testing of Materials, 3rd edn. ed., Springer-Verlag, New York, 1983.</mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple">Kulmyrzaev, A., Cancelliere, C., and McClements, D. J.: Characterization of aerated foods using ultrasonic reflectance spectroscopy, J. Food Eng., 46, 235–241, 2000.</mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple">Kuo, H. L.: Variation of Ultrasonic Velocity and Absorption with Temperature and Frequency in High Viscosity Vegetable Oils, Japanese Journal of Applied Physics, 10, 167–170, 1971.</mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple">Kushibiki, J., Akashi, N., Sannomiya, T., Chubachi, N., and Dunn, F.: VHF/UHF range bioultrasonic spectroscopy system and method, IEEE Trans. Ultrason., Ferroelec. Freq. Contr., 42, 1028–1039, 1995.</mixed-citation>
</ref>
<ref id="ref51">
<label>51</label><mixed-citation publication-type="other" xlink:type="simple">Kushibiki, J., Okabe, R., and Arakawa, M.: Precise measurements of bulk-wave ultrasonic velocity dispersion and attenuation in solid materials in the VHF range, J. Acoust. Soc. Am., 113, 3171–3178, 2003.</mixed-citation>
</ref>
<ref id="ref52">
<label>52</label><mixed-citation publication-type="other" xlink:type="simple">Lach, M., Platte, M., and Ries, A.: Piezoelectric materials for ultrasonic probes, NDTnet, 1, 1996.</mixed-citation>
</ref>
<ref id="ref53">
<label>53</label><mixed-citation publication-type="other" xlink:type="simple">Lynnworth, L. C. and Pedersen, N. E.: Ultrasonic mass flowmeter, Proc. IEEE Ultrason. Symp., 87–90, 1972.</mixed-citation>
</ref>
<ref id="ref54">
<label>54</label><mixed-citation publication-type="other" xlink:type="simple">Lynnworth, L. C.: Ultrasonic nonresonant sensors, in: Sensors – A Comprehensive Survey, edited by: Göpel, W., Hesse, J., and Zemel, J. N., Mechanical Sensors, VCH Publishers Inc., New York, 311–312, 1994.</mixed-citation>
</ref>
<ref id="ref55">
<label>55</label><mixed-citation publication-type="other" xlink:type="simple">Mak, D. K.: Comparison of various methods for the measurment of reflection coefficient and ultrasonic attenuation, British Journal of NDT, 33, 441–449, 1991.</mixed-citation>
</ref>
<ref id="ref56">
<label>56</label><mixed-citation publication-type="other" xlink:type="simple">Marczak, W.: Water as standard in the measurements of speed of sound in liquids, J. Acoust. Soc. Am., 102, 2776–2779, 1997.</mixed-citation>
</ref>
<ref id="ref57">
<label>57</label><mixed-citation publication-type="other" xlink:type="simple">Marks, G. W.: Acoustic Velocity with Relation to Chemical Constitution in Alcohols, The Journal of the Acoustical Society of America, 41, 103–117, 1976.</mixed-citation>
</ref>
<ref id="ref58">
<label>58</label><mixed-citation publication-type="other" xlink:type="simple">Mason, P., Baker, W. O., McSkimin, H. J., and Bepiss, J. H.: Measurement of Shear Elasticity and Viscosity of Liquids at Ultrasonic Frequencies, Phys. Rev., 75, 936–946, 1949.</mixed-citation>
</ref>
<ref id="ref59">
<label>59</label><mixed-citation publication-type="other" xlink:type="simple">Matson, J., Mariano, C. F., Khrakovsky, O., and Lynnworth, L. C.: Ultrasonic Mass Flowmeters Using Clamp-On or Wetted Transducers, 5th International Symposium on Fluid Flow Measurement, Arlington, Virginia, 2002,</mixed-citation>
</ref>
<ref id="ref60">
<label>60</label><mixed-citation publication-type="other" xlink:type="simple">McClements, D. J.: Ultrasonic Characterization of Foods and Drinks: Principles, Methods, and Applications, Critical Reviews in Food Science and Nutrition, 37, 1–46, 1997.</mixed-citation>
</ref>
<ref id="ref61">
<label>61</label><mixed-citation publication-type="other" xlink:type="simple">McClements, D. J. and Fairly, P.: Ultrasonic pulse echo reflectometer, Ultrasonics 29, 58–62, 1991.</mixed-citation>
</ref>
<ref id="ref62">
<label>62</label><mixed-citation publication-type="other" xlink:type="simple">McClements, D. J. and Fairly, P.: Frequency scanning ultrasonic pulse echo reflectometer, Ultrasonics, 30, 403–405, 1992.</mixed-citation>
</ref>
<ref id="ref63">
<label>63</label><mixed-citation publication-type="other" xlink:type="simple">Mc Gregor, K. W.: Methods of Ultrasonic Density Measurement, Australasian Instrumentation and Measurement Conference, Adelaide, S. Aust., 1989.</mixed-citation>
</ref>
<ref id="ref64">
<label>64</label><mixed-citation publication-type="other" xlink:type="simple">Moore, R. S. and McSkimin, H. J.: Physical Acoustics, Academic Press, New York, 167–242, 1970.</mixed-citation>
</ref>
<ref id="ref65">
<label>65</label><mixed-citation publication-type="other" xlink:type="simple">O&apos;Neil, H. T.: Reflection and Refraction of Plane Shear Waves in Viscoelastic Media, Phys. Rev., 75, 928–935, 1949.</mixed-citation>
</ref>
<ref id="ref66">
<label>66</label><mixed-citation publication-type="other" xlink:type="simple">Papadakis, E. P.: Correction for Diffraction Losses in the Ultasonic Field of a Piston Source, J. Acoust. Soc. Am., 31, 150–152, 1959.</mixed-citation>
</ref>
<ref id="ref67">
<label>67</label><mixed-citation publication-type="other" xlink:type="simple">Papadakis, E. P.: Buffer-Rod System for Ultrasonic Attenuation Measurements, J. Acoust. Soc. Am., 44, 1437–1441, 1968.</mixed-citation>
</ref>
<ref id="ref68">
<label>68</label><mixed-citation publication-type="other" xlink:type="simple">Papadakis, E. P., Fowler, K. A., and Lynnworth, L. C.: Ultrasonic attenuation by spectrum analysis of pulses in buffer rods: Method and diffraction corrections, J. Acoust. Soc. Am., 53, 1336–1343, 1973.</mixed-citation>
</ref>
<ref id="ref69">
<label>69</label><mixed-citation publication-type="other" xlink:type="simple">Pope, N. G., Veirs, D. K., and Claytor, T. N.: Fluid Density and Concentration Measurment using noninvasive in situ ultrasound resonance interferometry, Ultrasonics Symposium, 1992, 855–858, 1992.</mixed-citation>
</ref>
<ref id="ref70">
<label>70</label><mixed-citation publication-type="other" xlink:type="simple">Pope, N. G., Veirs, D. K., and Claytor, T. N.: Fluid density and concentration measurment using noninvasive in situ ultrasonic resonance interferometry, 5, 359, 541, United States, 1994.</mixed-citation>
</ref>
<ref id="ref71">
<label>71</label><mixed-citation publication-type="other" xlink:type="simple">Povey, M. J. W. and McClements, D. J.: Ultrasonics in Food Engineering. Part I: Introduction and Experimental Methods, J. Food Eng., 8, 217–245, 1988.</mixed-citation>
</ref>
<ref id="ref72">
<label>72</label><mixed-citation publication-type="other" xlink:type="simple">Püttmer, A. and Hauptmann, P.: Ultrasonic density sensor for liquids, Proc. IEEE Ultrason. Symp., 497–500, 1998.</mixed-citation>
</ref>
<ref id="ref73">
<label>73</label><mixed-citation publication-type="other" xlink:type="simple">Püttmer, A., Lucklum, R., Henning, B., and Hauptmann, P.: Improved ultrasonic density sensor with reduced diffraction influence, Sensors Actuators A, 67, 8–12, 1998.</mixed-citation>
</ref>
<ref id="ref74">
<label>74</label><mixed-citation publication-type="other" xlink:type="simple">Püttmer, A., Hoppe, N., Henning, B., and Hauptmann, P.: Ultrasonic density sensor–analysis of errors due to thin layers of deposits on the sensor surface, Sensor. Actuator., 76, 122–126, 1999.</mixed-citation>
</ref>
<ref id="ref75">
<label>75</label><mixed-citation publication-type="other" xlink:type="simple">Püttmer, A., Hauptmann, P., and Henning, B.: Ultrasonic density sensor for liquids, IEEE Trans. Ultrason., Ferroelec. Freq. Contr., 47, 85–92, 2000.</mixed-citation>
</ref>
<ref id="ref76">
<label>76</label><mixed-citation publication-type="other" xlink:type="simple">Raum, K., Ozguler, A., Morris, S. A., and O&apos;Brien, W. D. J.: Channel Defect Detection in Food Packages Using Integrated Backscatter ultrasound Imaging, IEEE Trans UFFC, 45, 30–40, 1998.</mixed-citation>
</ref>
<ref id="ref77">
<label>77</label><mixed-citation publication-type="other" xlink:type="simple">Rychagov, M. N., Tereshchenko, S., Masloboev, Y., Simon, M., and Lynnworth, L. C.: Mass Flowmeters for Fluids with Density Gradient, IEEE Ultrasonics Symposium, 465–470, 2002.</mixed-citation>
</ref>
<ref id="ref78">
<label>78</label><mixed-citation publication-type="other" xlink:type="simple">Sachse, W.: Density determination of a fluid inclusion in an elastic solid from ultrasonic spectroscopy measurements, Proc. IEEE Ultrason. Symp., 716–719, 1974.</mixed-citation>
</ref>
<ref id="ref79">
<label>79</label><mixed-citation publication-type="other" xlink:type="simple">Saggin, R. and Coupland, J. N.: Concentration Measurement by Acoustic Reflectance, J. Food Sci., 66, 681–685, 2001.</mixed-citation>
</ref>
<ref id="ref80">
<label>80</label><mixed-citation publication-type="other" xlink:type="simple">Schäfer, R., Carlson, J. E., and Hauptmann, P.: Ultrasonic concentration measurement of aqueous solutions using PLS regression, Ultrasonics, 44, e947–e950, 2006.</mixed-citation>
</ref>
<ref id="ref81">
<label>81</label><mixed-citation publication-type="other" xlink:type="simple">Silberman, E.: Sound Velocity and Attenuation in Bubbly Mixtures Measured in Standing Wave Tubes, J. Acoust. Soc. Am., 29, 925–933, 1957.</mixed-citation>
</ref>
<ref id="ref82">
<label>82</label><mixed-citation publication-type="other" xlink:type="simple">Sinha, D. N.: Noninvasive identification of fluids by swept frequency acoustic interferometry, 5, 767, 407, United States, 1998.</mixed-citation>
</ref>
<ref id="ref83">
<label>83</label><mixed-citation publication-type="other" xlink:type="simple">Sinha, D. N. and Kaduchak, G.: Chapter 8: Noninvasive determination of sound speed and attenuation in liquids, in: Experimental Methods in the Physical Sciences, Academic Press, 307–333, 2001.</mixed-citation>
</ref>
<ref id="ref84">
<label>84</label><mixed-citation publication-type="other" xlink:type="simple">Swoboda, C. A., Frederickson, D. R., Gabelnick, S. D., Cannon, P. H., Hornestra, F., Yao, N. P., Phan, K. A., and Singleterry, M. K.: Development of an Ultrasonic Technique to Measure Specific Gravity in Lead-Acid Battery Electrolyte, IEEE Transactions on Sonics and Ultrasonics, 30, 69–77, 1983.</mixed-citation>
</ref>
<ref id="ref85">
<label>85</label><mixed-citation publication-type="other" xlink:type="simple">Van Sint Jan, M., Guarini, M., Guesalaga, A., Ricardo Perez-Correa, J., and Vargas, Y.: Ultrasound based measurements of sugar and ethanol concentrations in hydroalcoholic solutions, Food Control, 19, 31–35, 2008.</mixed-citation>
</ref>
<ref id="ref86">
<label>86</label><mixed-citation publication-type="other" xlink:type="simple">Vray, D., Berchoux, D., Delachartre, P., and Gimenez, G.: Speed of Sound in Sulfuric Acid Solution: Application to Density Measurement, Ultrasonics Symposium, 465–470, 1992.</mixed-citation>
</ref>
<ref id="ref87">
<label>87</label><mixed-citation publication-type="other" xlink:type="simple">Wallhäußer, E., Hussein, M. A., Hinrichs, J., and Becker, T.: The acoustic impedance – an indicator for concentration in alcoholic fermentation and cleaning progress of fouled tube heat exchangers, 5th International Technical Symposium on Food Processing, Monitoring Technology in Bioprocesses and Food Quality Management, Potsdam, Germany, 1 September, 2009.</mixed-citation>
</ref>
<ref id="ref88">
<label>88</label><mixed-citation publication-type="other" xlink:type="simple">Wang, H., Cao, Y., Zhang, Y., and Chen, Z.: The design of The ultrasonic liquid density measuring instrument, Third International Conference on Measuring Technology and Mechatronics Automation, 2011.</mixed-citation>
</ref>
<ref id="ref89">
<label>89</label><mixed-citation publication-type="other" xlink:type="simple">Wang, Z. and Nur, A.: Ultrasonic velocities in pure hydrocarbons and mixtures, J. Acoust. Soc. Am., 89, 2725–2730, 1991.</mixed-citation>
</ref>
<ref id="ref90">
<label>90</label><mixed-citation publication-type="other" xlink:type="simple">Williams, A. O. J. and Labaw, L. W.: Acoustic Intensity Distribution from a &quot;Piston&quot; Source, J. Acoust. Soc. Am., 16, 231–236, 1945.</mixed-citation>
</ref>
<ref id="ref91">
<label>91</label><mixed-citation publication-type="other" xlink:type="simple">Williams, A. O. J.: The Piston Source at High Frequencies, J. Acoust. Soc. Am., 23, 1–6, 1951.</mixed-citation>
</ref>
<ref id="ref92">
<label>92</label><mixed-citation publication-type="other" xlink:type="simple">Yang, J.: Chapter 10: Temperature Sensors, in: Analysis of Piezoelectric Devices, World Scientific Publishing Co. Pte. Ltd., Singapore, 371–386, 2006.</mixed-citation>
</ref>
<ref id="ref93">
<label>93</label><mixed-citation publication-type="other" xlink:type="simple">\.Zak, A., Dzida, M., Zorb\ceski, M., and Ernst, S.: A high pressure device for measurements of the speed of sound in liquids, Rev. Sci. Instrum., 71, 1756–1765, 2000.</mixed-citation>
</ref>
</ref-list>
</back>
</article>