Ultrasound-based density determination via buffer rod techniques: a review

Abstract

Abstract. 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.

Critical process parameter of alcoholic yeast fermentation: speed of sound and density in the temperature range 5–30 °C

“…Concerning the measurement of the CPPs, a review of suitable methods to determine both density and USV noninvasively online is given in (Hoche et al ., ).…”

“…The actual study presents the CPP determination within a relevant range of process parameters for anaerobic yeast fermentation of malt‐based sugar solutions. The data are required to develop mathematical models to determine online the CQAs and to validate suitable measurement principles (Hoche et al ., ).…”

Ultrasound‐based, in‐line monitoring of anaerobe yeast fermentation: model, sensor design and process application

“…A more simple applicability is offered by the so-called buffer-rod techniques (BRT). As explained detailed in Hoche et al (2013), the description of ultrasound signals in terms of plane wave propagation through reference materials (buffer) of known properties and across one or more interfaces which are in direct contact with the liquid of interest, provides the determination of the reflection coefficient from medium 1 (buffer) to medium 2 (fluid), r 12 . Together with the liquid's sound velocity, the buffer's sound velocity and the buffer's density the liquid's density can be calculated:…”

P1.10 - Ultraschall – Etablierte Methodik oder innovative Messtechnik?

“…Im Vergleich zu anderen vorhandenen Techniken bietet Ultraschall eine schnelle, kostengünstige und nicht-destruktive Methode zur Analyse von Prozess-und Produktparametern [4][5][6]. Durch ihren nicht-invasiven Charakter bieten sich vielfältige Anwendungsgebiete, gerade in den produktsensiblen Prozessschritten der Life Sciences [7][8][9] und der Lebensmittelindustrie [10][11][12].…”