Acoustical temperature sensors

Acoustical temperature sensors can theoretically measure temperature from the cryogenic range to plasma levels. Their accuracy can approach that of primary standards. Temperature measurements can be made not only in gases but also in liquids or solids, on the basis of the relationship between the sound velocity and temperature shown in Figure 3.163. The acoustic velocity can be detected by immersing a rod or wire into the fluid or by using the medium itself as an acoustic conductor. The sensor rod can measure the temperature at a point or, by means of a series of constrictions or indents, can profile or average the temperature within the medium. 

For industrial fertilizer production reliable ammonia concentration data are essential. An experimental setup for acoustic chemometric prediction of ammonia concentration has been tested in a full-scale industrial plant. Figure 9.22 shows a bypass loop with the orifice plate. The acoustic sensor was again mounted onto the orifice plate [5]. To ensure constant differential pressure and temperature of the ammonia flow, two pressure transmitters and one temperature sensor were used. Reference samples were taken at the sample valve shown in Figure 9.22. 

There are several applications of ZnO that are due to its excellent piezoelectric properties [28,164]. Examples are surface-acoustic wave (SAW) devices and piezoelectric sensors [28,165-167]. Typically, SAW devices are used as band pass filters in the tele-communications industry, primarily in mobile phones and base stations. Emerging field for SAW devices are sensors in automotive applications (torque and pressure sensors), medical applications (chemical sensors), and other industrial applications (vapor, humidity, temperature, and mass sensors). Advantages of acoustic wave sensors are low costs, ruggedness, and a high sensitivity. Some sensors can even be interrogated wirelessly, i.e., such sensors do not require a power source. 

To some extent, progress has been limited by the availability of measurements on exchange processes. Until recently, temperature microstructure measurements were the primary approach to quantify near-surface turbulence. The instruments needed to do this were expensive and difficult to operate. The situation is now considerably improved. Microstructure sensors more suited to field use are commercially available, and are more user-friendly . Alternative methods to observe or infer mixing processes have also been perfected, including free-fall CTDs, acoustic doppler sensors and acoustically monitored floats. As these techniques are refined and deployment, operation, and analysis become more routine, it will become increasingly practical to incorporate a mixing component into field studies of UVR effects. 

Grate J W, Rose-Pehrsson S L, Venezky D L, Klusty M and Wohltjen H 1993 Smart sensor system for trace organophosphorus and organosulfur vapor detection employing a temperature-controlled array of surface acoustic wave sensors, automated sample preconcentration and pattern recognition Anal. Chem. 65 1868... 

For salt aqueous solutions in the absence of any other chemical additives, the hydrate suppression temperature (i.e., dissociation temperature shift) can be determined by measuring the electrical conductivity (Mohammadi, et al, 2007) [16], To characterize liquid mixtures for industrial processes, an acoustic multi-sensor system was developed to measure the concentrations of the chemicals such as MeOH and MEG in the solutions without salts (Henning, et al, 2000) [10]. However, these methods may not be applicable to most hydrocarbon transport pipelines where salts and at least one inhibitor often coexist in the aqueous phase. (Sandengen and Kaasa, 2006) [18] developed an empirical correlation that determined the MEG and NaCl concentrations by measuring the density and electrical conductivity of water samples under examination. However, the critical weakness of this method is that it requires high accuracy of the density measurement, which prevents it from application to real produced water samples that usually contain solid particles (sands and clays) and oil droplets. 

Gong Y, Radachowsky S, Wolf M, Nielsen M, Girguis P, Reimers CE. Benthic microbial fuel cell as direct power source for an acoustic modem and seawater oxygen/temperature sensor system. Environ Sci Technol 2011 45 5047-5053. 

Ferroelectrics and related materials are applied to elements of capacitor, piezoelectric transducer, pyroelectric temperature sensor, surface acoustic wave device and other devices. The recent important application is for non-volatile ferroelectric random access memories (NVFRAM). Many ferroelectric materials are used in the form of thin films. So far, most of the thin films of ferroelectric materials have been produced via gas phase. However, a great many number of works on sol-gel derived thin films of ferroelectrics have appeared since 15 years ago. 

Temperature sensors are constructional elements for measuring temperature and employ the functional dependence of a certain physical property of the sensor material on temperature, which is customarily recognized and well defined [672,673]. Practically, resistance or thermoelectric thermometers are most often used, whereas thermistors, ion thermometers, optical pyrometers and low-temperature gas, magnetic or acoustic thermometers are employed less frequently. 

Devices for converting nonelectrical effects and signals to electrical signals. This group includes numerous sensors for measuring and controlling the temperature, pressure, linear accelerahons, vibrahons, various mechanical and acoustic parameters, how rates and the consumption of liquids, and similar... 

Acoustic chemometrics has its greatest benefits in cases where haditional sensors and measurement techniques, such as flow, temperature and pressure transmitters cannot be used. In many processes it is preferable to use noninvasive sensors because invasive sensors may cause disturbances, for example fouling and clogging inside the process equipment such as pipelines, reactors cyclones, etc. In this chapter we concentrate mainly on new industrial applications for acoustic chemomehics, and only discuss the necessary elements of the more technical aspects of the enabling technology below - details can be found in the extensive background literature [3-5],... 

A model for crystallization point of the urea melt sprayed into the granulator was developed based on acoustic spectra recorded from sensor position A during a trial period of 24 hours. A flow sheet of the liquid urea feed process can be seen in Figure 9.7. Sensor A is mounted onto an orifice plate inserted in the main supply pipeline of liquid urea (see Figures 9.6 and 9.7). The reference values used to calibrate the model are the crystallization temperature (called the jc point ), as determined by the pilot plant laboratory (heat table visual nucleation/crystallization detection). 

A PLS regression model based on X (acoustic spectra from sensor A) and Y (crystallization temperature) was established. The X matrix contains 13 objects, each with 1024 variables (frequencies 0-25kHz). An overview of the X data is shown in Figure 9.8, in which one can observe systematic changes in the acoustic signatures following the object (samples) succession. 

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