Vibrating wire

FIGURE 4.41 Flow turbulence induced by a vibrating wire. Spark shadowgraph of 5.6% propane-air flame [after Markstein, Proc. Combust. Inst. 7, 289 (1959)]. 

The vibrating cylinder version of this type of transducer employs a sensing element of the straight tube type and is similar to the vibrating cylinder density meter (Section 6.6.1). The cylinder is maintained in oscillation by a feedback amplifier/limiter combination and its frequency of oscillation varies with the pressure of the fluid within it, which alters the hoop stress on the cylinder. As with the vibrating wire, the frequency of oscillation increases with the fluid pressure. In order to be able to use the sensor for the measurement of absolute pressures, it is surrounded with a cylindrical housing and the annular space between the two is evacuated. Such sensors give excellent repeatability and have a relatively low temperature sensitivity. 

Section 10.4.2 gives a detailed description of the behaviour and elec-troanalytical use of vibrating wire and band electrodes. In this section, some general remarks are given to link this discussion with the information presented above. 

Fig. 10.10. Schematic of the flow pattern around a vibrating wire (cross section).

Local impedance measurements represent another form of generalized transfer-function analysis. In these experiments, a small probe is placed near tiie electrode surface. The probe uses either two small electrodes or a vibrating wire to allow measurement of potential at two positions. Under the assumption that the electrolyte conductivity between the two points of potential measurement is uniform, the current density at the probe can be estimated from the measured potential difference AVprobe by... 

In the case of high pressures, different types of viscometer have been employed owing to the need to reduce the volume of fluid required. The most popular have been falling-body viscometers and torsional-crystal viscometers. Neither of these have, however, completely developed theories so that their accuracy is intrinsically limited. On the other hand, the newly developed vibrating-wire viscometer that makes use of the damping of a transverse oscillation of a thin wire enjoys a complete theory. 

K. W. Pratt and D. C. Johnson, The Vibrating Wire Electrode as am Am-perometric Detector for Flow Injection Systems. Anal. Chim. Acta, 148 (1983) 87. 

Measurements are taken on the three principal joint directions and in 6-cm diameter boreholes. Each measurement point corresponds to two boreholes, both perpendicular to the joints and 20 cm apart (see Fig. 3). A pressure gauge for measuring hydrostatic pressure is placed in the first borehole and a vibrating wire extensometer is installed in the second in order to monitor deformation normal to the joint. This extensometer is positioned within a concrete cylinder. The deformation measurement is thus that of the cylinder with a 6-cm diameter and 50-cm length. The recorded deformations are then transformed into normal displacements by referring to the basic measurement length, i.e. the 15-cm extensometer length. 

When the green set is sufficiently advanced and the cake is of the required consistency, the mould is removed and the cake is trimmed/cut into blocks by oscillating, or vibrating, wire saws. Surplus materials (off-cuts or returns) are recycled to the mixer, as already mentioned. If, however, cutting is delayed, the mix eventually becomes too hard to be cut and must be scrapped. Thus the cutting window is an important factor in the routine operation of the process. The use of lime as part of the binder increases the period during which the mix can be cut. 

Viscosity measurement methods for polymers under high-pressure CO2 may be divided into four classes pressure driven, falling body, rotational devices, and vibrating wire. Accurate viscosity measurements require a homogeneous solution to be prepared, thus ensuring that phase separation does not occur [19, 76]. 

It may be necessary to install a blanket drain of high-permeability material. A geotex tile filter blanket may have to be installed to separate the waste rock from cycloned sand. To monitor the structural integrity of the dam, vibrating wire piezometers (VWPs) may be installed beneath the foundation of the dam. The VWP should be placed in the blanket drain, within the starter dam and within the cycloned sands. 

Weekly measurement of pore water pressure by the vibrating wire piezometer method. 

Fig. 9.9. Illustrating the wavelength of the wave set up in a vibrating wire, the distance between two cooseciyftVe crests, AS. 

Although the word "wave connotes a visible shape like that of a water wave or a vibrating wire Fig. 6.6), no material form or shape or sequence of waves need be imagined. Unlike a water wave, matter is not required for the transmission of electromagnetic waves. 

Keywords Gas sorption Glass transition High pressure Self-assembling Solubility Transitiometry Vibrating-wire technique... 

HIGH PRESSURE VESSEL HOUSING THE MEASURING CELL EQUIPPED WITH THE VIBRATING WIRE WHICH SUSTAMS THE POiTMER SAMPLE... 

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