Wire Probes

For various reasons, this type of anemometer is not a suitable instrument for practical measurements in the industrial environment. The thin wire probe is fragile and sensitive to contamination and is unsuited to rough industrial environments. The wire temperature is often too high for low-velocity measurements because a strong natural convection from the wire causes errors. Temperature compensation, to correct for ambient air temperature fluctuations may not be available or may not cover the desired operating range. 

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). 

FIGURE 14.14 Photographs of a typical volumetric unit. The complete unit is shown on the left and a close-up of the titration vessel on the right. The dual platinum wire probe is visible in the right photograph as is the tube (dark in color) that introduces the titrant to the solution. 

Campos (Ref 23) examined a measurement technique that uses a resistive wire probe to... 

Calzia Carabin (Ref 38) and Calzia (Ref 60) studied DDT in RDX using wire-probe and... 

Thermal flowmeters can be divided into the following two categories (1) flowmeters that measure the rise in temperature of the fluid after a known amount of heat has been added to it, which can be called heat transfer flowmeters and (2) flowmeters that measure the effect of the flowing fluid on a hot body, which are sometimes called hot-wire probes, or heated-thermopile flowmeters. 

In hot-wire probe designs, the cooling effect of the flowing process gas stream is detected, as was already discussed in connection with anemometers (see Figure 3.50). A major limitation of the hot-wire-type mass flowmeters is that they do not detect the mass flow across the full cross section of the pipe, but do so only at the tip of the sensor. Therefore, if the sensor is installed in a nonrepresentative location, the resulting reading will be in error. 

Fig. 5. Ti21+ Lyman-a from EBIT and V Ka from wire probe on a common wavelength scale...

Fine deformed microstructures with strong preferred orientations could be produced by a single stroke of the wire probe (25), as illustrated by Figure 17. A vertical section made on a specimen quenched immediately after deformation confirmed that the underlying structure was fibrous with tt and 2tt wedge disclinations (30). The relaxation or coarsening after deformation indicated that the mesophase was sufficiently fluid for disclination motion... 

Figure 17 Formation and relaxation of deformed microstructure, after a single stroke by the wire probe on the hot stage (25). Crossed polarizers.

The propellant grains are in the form of thin rods ( strands ) which may have been cut or extruded and protected against surface burning by mantle insulation. The strand is placed in a bomb and electrically initiated at one end, after which its combustion rate is recorded with the aid of wire probes. Using compressed nitrogen, the pressure at which the combustion take place is adjusted in the bomb standard values are 20, 40, 70, 100, 130, 180, 250 bar at a temperature between -40 °C and 60 °C. 

The weight of catalyst in a vessel is determined by measuring the pressure differential between taps installed at the top and bottom. Density of the fluidized catalyst is determined in a similar manner from the differential pressure between taps located a measured distance apart in the dense phase. Location of the catalyst level can be determined from the combination of the density and the total weight of catalyst, or by the use of a series of pressure taps placed at intervals along the height of the vessel. A hot-wire probe has been used to locate the level in laboratory fluidized beds (250), but this technique has not been adopted for fluid cracking units. The method depends upon the fact that heat-transfer rate from the heated wire is much higher when immersed in the dense phase of fluidized solids than when in the dilute phase. 

The influence of wake motion on bulk turbulence induced in the liquid is understood more clearly by inspecting oscillograms which show the fluctuation of local liquid velocity. Figure 43 shows such oscillograms taken by Kikuchi (K30) with a hot-wire probe. The bubble column is 8.0 cm in diameter, water-filled to a 170-cm height, with the probe 115 cm above the bottom gas distributor. In the column bubbles of constant volume (100 cc) are injected successively at constant time intervals, either at 2.1 sec (case a) or 0.50 sec (case b). Case c is an example of continuous bubbling at f/c = 6.45 cm/sec. 

As the size of the metastable region and the number of relaxation times by all the signs increase, the use of quasi-static methods becomes unacceptable. It is probably for this reason in part that research into not fully stable states of complex systems (mixtures and thermally unstable fluids ) progresses very slowly. To solve the problem, we are developing the method of controlled pulse heating of a thin wire probe - resistance thermometer. 

Figure 2. The method ofcontrolled pulse heating ofa thin wire probe characteristic heating curves in the constant power mode P(t)-const (2a) and the temperature plateau one Tpi = T(t > tg) -const (2b). Here tg is the time period required for transition to the regime. Here ami further, arrows show the moment of spontaneous boiling-up (t = t ) for the liquids.

Figure 4.9 Apparatus to measure permselectivity (transport number of X relative to chloride ions of an anion exchange membrane). C cation exchange membrane A anion exchange membrane to be measured 1,4 Ag—AgCl electrodes for current supply 2,3 Ag—AgCl wire probe electrodes to measure the voltage drop across the membrane.

Alternatively, heat release to a calorimeter wire probe has been used as an indicator of chlorine atoms. 

Figure 37.2 demonstrates the electric field pulse produced by a figure-of-eight coil, as measured by a two-wire probe in a brain phantom filled with saline solution at physiologic concentration. In repetitive TMS (rTMS), several such pulses are administered in a train of between 1 and 20 Hz. 

Durst F, et al. 2003. The development of a pulsed-wire probe for measuring flow velocity with a wide bandwidth. International Journal of Heat and Fluid Flow, 24(1) 11-13. 

Four steel wire probes coated with Lacomate insulator were planted in the repair mix at different depths, that is, 5,10,15, and 20 mm. Half-cell potential measurements were made between the corroded main bar and the four probes after wet and dry cycles using saline water. It can be seen clearly that the potentials of the probes did not increase sharply. It showed a trend of increasing corrosion activities in the steel wires and slight reduction in the corrosion activities in the bolts, connected to the main steel reinforcement bar. 

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