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The objective of this paper is to measure the zero-flow offset variation in ultrasonic Clamp-on flowmeters produced by using pipes made of materials with a nonhomogeneous and nonlinear behavior. The evaluation of this phenomenon has been tested by the experimental measurement, the experiments consist of measuring the variation in the flow measurement when in ``no-flow condition,'' the transducers are moved along the pipe. Experimental results reveal that the reciprocity criterion is not fulfilled when nonhomogeneous and nonlinear pipe materials are used. Consequently, in these types of pipes materials, it is necessary to calibrate the offset when transducers are installed, and probably will need recalibration if the transducers are displaced to another position on the pipe. However, in installations, where it is not possible to stop flow in order to calibrate, the flowmeter will have an error in the measured value and this error will depend on the acoustic characteristics of the pipe material.

During malolactic fermentation in wines, malic acid is transformed into lactic acid by the action of lactic acid bacteria. This process can be monitored on-line by measuring the velocity of a low intensity ultrasonic wave propagating through the medium. In this work, an experimental study of ultrasonic propagation velocity in laboratory mixtures of water–ethanol–malic acid and lactic acid is presented. A good correlation was found between the ultrasonic velocity and malic and lactic acid concentrations. These results could be used to predict the end-point of the malolactic fermentation process and show the great potential of this ultrasonic technique to determine malic and lactic acid concentrations during the malolactic fermentation process.

Ultrasound is an emerging technology that can be applied to monitor food processes. However, ultrasonic techniques are usually limited to research activities within a laboratory environment and they are not extensively used in industrial processes. The aim of this paper is to describe a novel ultrasonic sensor designed to monitor physical–chemical changes that occur in wines stored in industrial tanks. Essentially, the sensor consists of an ultrasonic transducer in contact with a buffer rod, mounted inside a stainless steel tube section. This structure allows the ultrasonic sensor to be directly installed in stainless steel tanks of an industrial plant. The operating principle of this design is based on the measurement of ultrasonic velocity of propagation. To test its proper operation, the sensor has been used to measure changes of concentration in aqueous samples and to monitor the progress of a malolactic fermentation of red wines in various commercial wineries. Results show the feasibility of using this sensor for monitoring malolactic fermentations in red wines placed in industrial tanks.

Clamp-on ultrasonic flowmeters geometry includes four different materials in the ultrasound propagation path: wedge, coupling material, pipe and liquid. In this case, oblique incidence ultrasonic beam generated by the emitter transducer is split into several paths caused by multiple reflections in pipe wall or because of propagation mode conversion at interfaces. These multiple paths are recombined at the reception transducer aperture, producing a single signal whose amplitude and phase depend on which proportion each path contributes. The objective of this paper is to quantify this phenomenon and analyses the implications it has on the accuracy of Clamp-on ultrasonic flowmeters as a function of the fluid that flows inside the pipe. According to simulations, based on 2D ray tracing model and experimental measurements, the variations in the recombination signal at the reception transducer produces a linearity error that in case of the installation under test, Z-mode transducers configuration on PVC pipe, could reach a value of 3.2%.

This article is focused on the characterization of the lack of homogeneity in the dispersive acoustic properties of polymeric materials used in industrial pipes. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this paper, studies the variation in the propagation velocity, as a function of the intensity of the acoustic signal. In these cases, pipes made of PVC, PP and PVDF, which are commonly used in industrial installations, have been characterized. For each type of pipe, high and low acoustic intensity signals have been applied in order to reproduce working conditions that typically appear in the pipe wall below the transducers in commercial Clamp-on ultrasonic flowmeters (UFMs). Under these conditions, acoustic velocity maps have been created for the three materials under test. These maps reveal two effects that are not usually taken into account. The first one is the variation of the propagation velocity with the power density of the ultrasonic signal and the second one is the nonhomogeneous behaviour along the pipe surface. Finally, the acoustic maps reflect how a stronger acoustic signal produces greater behaviour differences in the materials under test. The characterized phenomenon of lack of homogeneity in dispersive acoustic properties, produces a variation in the zero flow error in Clamp-on UFM caused, so as not to fulfil the reciprocity criterion.

This paper presents a comparison between two algorithms for sinusoidal signal characterization applied to QCM impedance measurements. These algorithms are the zero crossing and peak detection method and the 7 parameters sine-fitting method. Simulation and experimental results from both methods are shown in order to determine which method provides the best performance in terms of accuracy. Obtaining a precise value of the QCM impedance depends directly on the precise measurement of the amplitude and phase of two sinusoidal voltages. It was found that the sine-fitting method achieves better results without an excessive associated computational burden. These results will be applied to the development of a new technique for biofilm characterization based on multiple QCM impedance measurements.

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This article analyses and explains the implications that dispersive materials have over the linearity in flow measurement when a Clamp-on ultrasonic flowmeter is used. This is of capital importance because dispersive materials are commonly used in the manufacture of transducer wedges and pipes. The evaluation of this phenomenon has been tested by experimental measurement. The used setup consisted of a water flow calibration facility where a commercial Clamp-on ultrasonic flowmeter was installed on it and its flow measurement was compared with a reference flowmeter. Two experiments have been conducted. A first experiment was performed to evaluate only the effect produced by the fact that the transducer wedge is made of dispersive material. For this reason, an ultrasonic flowmeter was installed on a pipe made of non-dispersive material, in this case, an INOX pipe. Linearity error introduced by the wedge was below 1%. This error complies with the accuracy specification of the ultrasonic flowmeter given by the manufacturer (±1.5%). Finally, a second experiment consisted of installing the ultrasonic flowmeter on a dispersive pipe (PVC pipe) in order to measure the worst condition (both materials, wedge and pipe, were dispersive). Under this condition, the linearity error was increased until it reaches a value of 6.4%. Moreover, in case of a dispersive material pipe, the bigger the pipe thickness is, the bigger non-linearity error is reached.

The progress of malolactic fermentation in red wines has been monitored by using ultrasonic techniques. The evolution of ultrasonic velocity of a tone burst 1 MHz longitudinal wave was measured, analyzed and compared to those parameters of oenological interest obtained simultaneously by analytical methods. Semi-industrial tanks were used during measurements pretending to be in real industrial conditions. Results showed that the ultrasonic velocity mainly changes as a result of the conversion by lactic acid bacteria of malic acid into lactic acid and CO2. Overall, the present study has demonstrated the potential of the ultrasonic technique in monitoring the malolactic fermentation process. (C) 2014 Elsevier B.V. All rights reserved.

This article explains how a multi-frequency ultrasonic beam path is split due to passing through dispersive materials and the implications that it has in flow measurement using a Clamp-on ultrasonic flowmeter. The importance of knowing this phenomenon is because dispersive materials are commonly used in the manufacture of transducer wedges and plastic pipes. Splitting of the ultrasonic beam path occurs when the incident angle is not normal to the surface of the pipe and a coupling wedge is necessary. The diffraction angle is produced at the boundaries among materials with different propagation velocities (according to Snell’s law), and furthermore, in dispersive materials, the propagation speed depends on frequency. Therefore, when the excitation signal contains several frequential components, each frequency travels with a different velocity. Under this circumstance, different diffraction angles are produced for each frequency at the boundaries between materials. As a result of splitting the path, the ultrasonic beam widens and the reception transducer aperture becomes too small to receive all the frequential components contained in the ultrasonic beam. Thus, when the ultrasonic beam is carried by the liquid flowing inside the pipe, the reception transducer receives different frequential contributions, producing change in its spectral composition. As a consequence of the mixing of these frequencies, the reception signal is modulated in phase and amplitude. Moreover, modulation will change as a function of frequential composition that is combined at the reception transducer. This is the origin of the linearity error in Clamp-on ultrasonic flowmeters.

This paper experimentally demonstrates the viability of Lamb waves generation and detection in metallic plates using ultrasonic air-coupled concave array transducers. For this purpose, a self-developed air-coupled Lamb wave NDT system has been used in three different metallic plates, such as stainless steel, copper and brass. First, pure copper plates were used to calibrate the measuring system and then other tests were performed in 304 stainless steel and CW508L brass. The obtained Lamb waves confirm the theoretical values, both in the phase velocity and in the group velocity measurements. In addition, a complete study of the errors in the measurements is also provided.

This paper investigates low cost matching network for high impedance ultrasonic transducers. Matching the output transmitter impedance to high impedance transducer is important to maximize the transfer of power and improve the transmitting efficiency of the transducer, and so achieve better signal-to-noise ratio. In NDT ultrasonic applications based on piezoelectric transducers it is usual to introduce a tuned inductor, normally fitted in an experimental way, in order to cancel out the reactive component of the impedance of the transducer. More elaborated tuning solutions are well known, but in systems employing several transducers, such as arrays, is not feasible to connect all the transducer elements via a transformer or a complex network to their transmitters. Therefore, when the number of components is critical, if the system works in a narrow frequency range, this paper proposes to employ a simple L-C matching network with only one inductor and one capacitor. This topology is evaluated, by means of equivalent circuit analysis, computer simulation, and experimental assessment.

Ultrasonic properties of materials present a strong dependence on temperature and in turn the ultrasonic velocity of propagation in the material under test. It is precisely for this reason that most ultrasonic measurements are often carried out with thermostated samples by using either water tanks or climate chambers. This approach is viable in a laboratory and when the measured or characterized samples are relatively small. However, this procedure is highly improbable to be applied when in situ measurements in industrial environments must be performed. This goes for the case of, for example, ultrasonic velocity measurements in wine while it is performing malolactic fermentation inside a tank of hundreds of thousands of litres. In this paper two different practical approaches to temperature compensation are studied. Then, the two temperature compensation methods are applied to the measured ultrasonic velocity values along a whole malolactic fermentation process. The results of each method are discussed.

Many ultrasonic sensors intended for non-destructive testing include a plastic or metal element, known as buffer rod, between the ultrasonic transducer and the material under analysis. Buffer rods are often terminated in the form of a conical tip for ultrasonic inspection of liquid-like substances. The conical tip is carefully shaped in a 45?? angle to favour the in phase reception of all the components of the ultrasonic wave reflected at the buffer tip, obtaining thus a maximum amplitude measurement signal. The effect of the buffer rod cone angle on measurement signals is studied in this work. A straightforward approximate formula for the effect of the error angle on measurement signal amplitude is used. Simulations are performed using a two-dimensional finite differences tool. Measurements are conducted with the same operating conditions and buffer rod materials and dimensions as those defined for both approximate formula evaluation and simulations. Thus, a comparison of the approximate formula, simulation and measurement results are established. Furthermore, the significance of some parameters such as ultrasonic transducer operating frequency and diameter, and buffer rod material are also analysed. The obtained results show that significant loss of the measurement signal amplitude is found only for cone error angles beyond the range of usual machining errors.

Buffer rods are usually plastic or metallic solid cylinders of known acoustic properties, which are placed between the ultrasonic transducer and the sample under study. For some applications, the buffer rod end in contact with the sample under inspection is shaped in a form of a conical tip. If the cone angle is fixed to 45°, the components of the ultrasonic wave reflected at the buffer conical tip are received at the transducer in phase, forming thus a maximum amplitude signal. Otherwise, the components of the ultrasonic wave are received out of phase, composing thus a weaker signal. In this work, the effect of the buffer rod cone angle on the measurement signals has been studied by means of simulations and experiments. The simulations were performed using a two-dimensional finite differences tool and the measurements were conducted with the same operating conditions and buffer rod materials and dimensions than those defined for simulations. The influence of some aspects such as ultrasonic transducer operating frequency and diameter, and buffer rod material has also been analyzed.

In the winemaking process, the malolactic fermentation is an essential process in the production of high quality red wines which concerns the conversion of malate into lactate. In this work, the ultrasonic velocity through wine samples with different concentrations of malate and lactate was measured using the pulse echo technique with 1 MHz tone burst signals. The evolution of these concentrations during malolactic fermentation was taken into account in order to determine the ratio between concentrations of malate and lactate of the different samples. These preliminary results have revealed that the ultrasonic velocity increases during the conversion of malate to lactate. In addition, measurements have been conducted to quantify the influence of variations in turbidity and temperature on test samples. Therefore, these results show the possibility of using ultrasonic velocity measurements for on-line monitoring the malolactic fermentation of red wine and may help to improve and contribute to the development of the winemaking process.

Many varieties of bread are prepared using flour coming from wheat. However, there are other types of flours milled from rice, legumes and some fruits and vegetables that are also suitable for baking purposes, used alone or in combination with wheat flour. The type of flour employed strongly influences the dough consistency, which is a relevant property for determining the dough potential for breadmaking purposes. Traditional methods for dough testing are relatively expensive, time-consuming, off-line and often require skilled operators. In this work, ultrasonic analysis are performed in order to obtain acoustic properties of bread dough samples prepared using two different types of flour, wheat flour and rice flour. The dough acoustic properties can be related to its viscoelastic characteristics, which in turn determine the dough feasibility for baking. The main advantages of the ultrasonic dough testing can be, among others, its low cost, fast, hygienic and on-line performance. The obtained results point out the potential of the ultrasonic analysis to discriminate doughs of different types of flour.

A comparison of methods for measuring time-of-flight (TOF) variations of ultrasonic waves travelling through food materials is presented. Six commonly used methods for the TOF determination were taken into account, four in the time domain and two in the frequency domain. First, methods were briefly described and then tested using simulated ultrasonic waves. Factors such as signal-to-noise ratio (SNR), attenuation and delay between signals are taken into consideration, whereas the root mean-squared error (RMSE) and execution time are used as parameters for comparison. Of the six methods, the one operating on the basis of phase shift proved to be the most robust and provided excellent levels of resolution and optimum performance across a wide range of SNR values. Experiments were subsequently conducted in a real process, which corroborated the results obtained during the theoretical study. The ability to accurately measure TOF variations of ultrasonic waves makes it possible to detect more precisely velocity variations, which is the most commonly used parameter to determine and acoustic monitor physicochemical changes and properties of food materials.

The demand for powder metallurgy (P/M) parts in its traditional automotive market is predicted to grow, but future sector expansion depends directly upon its capability to manufacture zero-defect parts for industries such as aerospace and medicine. The lack of adequate inspection systems has important implications from the point of view of quality assurance, since it increases the costs, time and wasted material. In recent years the applicability of several techniques for the inspection of P/M parts has been investigated, such as Eddy current testing, computer tomography or X-ray imaging, but studies have revealed that all of them have deficiencies that make them unavailable for a complete and reliable flaw detection and density defect recognition. A new inspection tool has been developed based on pulse echo ultrasonic technology combined with robotics, which makes it possible to provide a global density map of sintered.

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Quartz crystal microbalance (QCM) sensors are becoming a good alternative to analytical methods for the measurement of bacterial growth in liquid media culture. For this purpose, two essential resonance parameters allow monitoring of biofilm formation: the series resonance frequency shift and the change of the resistance at this frequency. Nevertheless, several problems arise in determining these parameters, as their relative variation is very small. This means that an accurate procedure must be implemented for the measurement of the QCM resonance parameters, including the automatic calibration of the frequency response effects of the measurement circuits and the automatic compensation of the static electrical capacitance of the QCM. In this paper, a novel multichannel system for on-line monitoring of biofilm formation based on QCM sensors is proposed. QCM resonance parameters are determined from the electrical impedance analysis by means of an auto-balanced impedance bridge. This configuration has allowed the implementation of an affordable multichannel measurement instrument. Obtained results, based on binary mixtures of water-glycerol measurements and real microorganism experiments, are in good agreement with the theoretical behaviour. These results show the great potential of this instrument to be used for monitoring microbial growth and biofilm formation.

Buffer rods can be used to perform non-destructive and on-line analysis of food and beverage products. These rods, usually solid cylinders, can be long and heavy for certain applications. In this paper, a resizing analytic procedure is described. Buffer rods designed following this new procedure can be several times shorter than the conventionally designed ones, optimising thus their weight and cost. The signal to noise ratio (SNR) of the resized buffers is also studied in order to determine their practical usability. To this effect, simulations and experiments are conducted using metal and plastic buffer rod materials appropriate for food and beverage testing such as aluminium and polyethylene.