Electrical conductivity probe

Electrical conductance probes These can be either flush probes or wire probes. Flush probes are imbedded in a nonconducting wall, with one electrode connected to a voltage source and the second through a precision resistor to ground (Telles and Dukler, 1970 Chu and Dukler, 1974). Wire probes use closely spaced, nearly parallel conducting wires of small diameter, which are positioned normal to the flow (Brown et al., 1978). 

Direct measurement of concentration fluctuations for liquid flow in packed and fluidized beds have been made by Hanratty et al. (H4), Prausnitz and Wilhelm (P12), Cairns (Cl), and Cairns and Prausnitz (C4). Detailed descriptions of electrical conductivity probes used for measurement of these fluctuations have been given by Prausnitz and Wilhelm (Pll) and Lamb et al. (LI). 

Local axial and radial gas-phase characteristic measurements were made at steady-state conditions in a 0.108-m-i.d. slurry bubble column apparatus with a two-point electrical conductivity probe. 

Figure 3. Electrical conductivity probe circuit and data acquisition system.

Improved instrumentation can improve control by measuring more directiy the variables governing the internal behavior of the mill. By installing an electrical conductivity probe in the wall of the mill, Moys and Montini [CIM Bulletin, 80(907), 52-6 (1987)] were able to detect the position of the ball mass during dynamic operation. This together with on-line measurement of slurry viscosity (see rheological properties, p. 20-32d) made it possible to control the mill at the desired operating point. 

Linek and Mayrhoferova (L16) have used electric conductivity to measure the dispersion height, based on locating the surface elevation at certain selected points by means of an electrically conductive probe. The height is determined by the vertical position of the probe tip for which the integrated time of contact is exactly half the period of measurement. The accuracy of the measured value of the total surface elevation is claimed by... 

An important technique in studying the mechanism of fully developed boiling is to use electrical conductance probes that can be traversed from the bulk fluid to the surface. A tiny needle tip (typically less than 50 pm in diameter) will record the local presence of liquid or vapor, and the fraction of time spent in contact with the vapor gives the void fraction, typical of the measurements of this type are those of Shoji [100], illustrated in Figs. 15.49 and 15.50. 

Bamea, D., Shoham, O., and Taitel, Y., "Flow Pattern Characterization in Two-phase Flow by Electrical Conductance Probe," International J. of Multiphase Flow, 7, 387-397 (1980). 

A sharp interface was established and maintained between the char and acceptor fluidized beds at the bottom of the gasifier. This was monitored by a specially designed electrical conductivity probe. 

Fig. 5. Three-stage thermostatted flotation column (25 mm diameter). P feed R liquid outlet with protein residue S foam liquid outlet gas inlet 1 glass frit 2 thermostat 3 perforated plates with overflow and down-comer 4 liquid level in the three stages 5 electrical conductivity probe and 6 foam breaker (3000 rpm) [70]...

The local relative gas holdup was measured by electrical conductivity probes (see 2.2). 

The most bubble size distributions were measured with flash photography and semiautomatic evaluation of the photographs (27,29). Miniaturized electrical conductivity probes with two sensors and on-line computer evaluation are also popular (27,28,29). 

Measurement of the moisture content of sinter feed with feedback to direct water additions at various mixing points is thus an essential part of good sinter machine control. Various devices are used for online moisture measurement, including infrared devices and electrical conductivity probes. The latter are most common and can simply be two trailing electrodes in contact with the feed material on a conveyor belt. These devices are not highly reliable and need careful and regular calibration since they are affected by the presence of soluble salts, which can change the electrical conductivity of the free interstitial water in the sinter bed. 

Skelland and Moeti (1990) and Skelland and Xien (1990) measured mass transfer rates using an electrical conductivity probe for drops suspended in an agitated vessel. Results of 180 different systems were correlated by... 

For the carbonation reaction, the slurry is placed in a double walled reactor equipped with a stirrer, a pH probe and an electrical conductivity probe (Fig. 1). The slurry is heated to the desired temperature for the carbonation reaction (55-90 C) by circulating a warm fluid in the double wall of the reactor. The stirring is started and once the temperature has reached the targeted value, the injection of the CO2 containing gas is started. This gas is injected into the slurry through a valve located at the bottom of the reactor. The gas is a mixture of air and CO2, containing between 15 and 50 vol % of CO2. The flow of CO2 is varied between 2.5 and 15 dm /min/kg of hydrated dolime in the suspension. 

Rhoades JD, van Schilfgaarde J (1976) An electrical conductivity probe for determining soil salinity. Soil Sci Soc Am J 40 647-651... 

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