Electrical conductivity limiting

Measurement by Electromagnetic Effects. The magnetic flow meter is a device that measures the potential developed when an electrically conductive flow moves through an imposed magnetic field. The voltage developed is proportional to the volumetric flow rate of the fluid and the magnetic field strength. The process fluid sees only an empty pipe so that the device has a very low pressure drop. The device is useful for the measurement of slurries and other fluid systems where an accumulation of another phase could interfere with flow measurement by other devices. The meter must be installed in a section of pipe that is much less conductive than the fluid. This limits its appHcabiHty in many industrial situations. 

Because there are two changes ia material composition near the active region, this represents a double heterojunction. Also shown ia Figure 12 is a stripe geometry that confines the current ia the direction parallel to the length of the junction. This further reduces the power threshold and makes the diffraction-limited spreading of the beam more symmetric. The stripe is often defined by implantation of protons, which reduces the electrical conductivity ia the implanted regions. Many different stmctures for semiconductor diode lasers have been developed. 

Disadvantages associated with some organic solvents include toxicity flammabiHty and explosion ha2ards sensitivity to moisture uptake, possibly leading to subsequent undesirable reactions with solutes low electrical conductivity relatively high cost and limited solubiHty of many solutes. In addition, the electrolyte system can degrade under the influence of an electric field, yielding undesirable materials such as polymers, chars, and products that interfere with deposition of the metal or alloy. 

Common conductive polymers are poly acetylene, polyphenylene, poly-(phenylene sulfide), polypyrrole, and polyvinylcarba2ole (123) (see Electrically conductive polymers). A static-dissipative polymer based on a polyether copolymer has been aimounced (124). In general, electroconductive polymers have proven to be expensive and difficult to process. In most cases they are blended with another polymer to improve the processibiUty. Conductive polymers have met with limited commercial success. 

Early models used a value for that remained constant throughout the day. However, measurements show that the deposition velocity increases during the day as surface heating increases atmospheric turbulence and hence diffusion, and plant stomatal activity increases (50—52). More recent models take this variation of into account. In one approach, the first step is to estimate the upper limit for in terms of the transport processes alone. This value is then modified to account for surface interaction, because the earth s surface is not a perfect sink for all pollutants. This method has led to what is referred to as the resistance model (52,53) that represents as the analogue of an electrical conductance... 

Specifications for gas turbine fuels prescribe test limits that must be met by the refiner who manufactures fuel however, it is customary for fuel users to define quality control limits for fuel at the point of delivery or of custody transfer. These limits must be met by third parties who distribute and handle fuels on or near the airport. Tests on receipt at airport depots include appearance, distfllation, flash point (or vapor pressure), density, freezing point, smoke point, corrosion, existing gum, water reaction, and water separation. Tests on delivery to the aircraft include appearance, particulates, membrane color, free water, and electrical conductivity. 

Graphite properties conducive to successful electrolytic appHcation include high electrical conductivity, high degree of insolubiUty and operation at low voltage, high purity, low initial cost, easily machinable, and few limitations as to size and shape. 

Table 12. Solubility Limits and Electrical Conductivity Effects of Elemental Additions to Copper ...

A metal being used for the purpose of current carrying must be checked for its conductivity. This is proportional to its current-carrying capacity. This will ascertain the correctness of size and grade of the metal chosen for a particular duty. It is necessary to avoid overheating of the conductor during continuous operation beyond the limits in Table 28.2. The electrical conductivity of a metal is reciprocal to its resistivity. The resistivity may be expressed in terms of the following units ... 

Electromagnetic (EM) Conductivity Measures the electrical conductivity of materials in microohms over a range of depths determined by the spacing and orientation of the transmitter and receiver coils, and the nature of the earth materials. Delineates areas of soil and groundwater contamination and the depth to bedrock or buried objects. Surveys to depths of SO to 100 ft are possible. Power lines, underground cables, transformers and other electrical sources severely distort the measurements. Low resistivities of surficial materials makes interpretation difficult. The top layers act as a shunt to the introduction of energy info lower layers. Capabilities for defining the variation of resistivity with depth are limited. In cases where the desired result is to map a contaminated plume in a sand layer beneath a surficial clayey soil in an area of cultural interference, or where chemicals have been spilled on the surface, or where clay soils are present it is probably not worth the effort to conduct the survey. 

Many liquid alloys, in particular, the alkali-group IV alloys, exhibit (Zintl) anion clustering and show strong effects of compound formation. A typical example of such Zintl systems are sodium-tin alloys. In the solid NaSn crystal the Zintl anions Sn appear [1]. An interesting question is the stability of these anions in the liquid. Furthermore, the electrical conductivity of these alloys shows a strong dependence on composition [2] For the limiting (sodium-rich or tin-rich) cases a metallic (small) conductivity appears, but for the nearly equimolar compositions a semi-metallic behavior - with a considerably smaller conductivity - is observed. 

Silver is often preferred as an undercoat for rhodium by reason of its high electrical conductivity. A further advantage of silver in the case of the thicker rhodium deposits (0-0025 mm) applied to electrical contacts for wear resistance is that the use of a relatively soft undercoat permits some stress relief of the rhodium deposit by plastic deformation of the under-layer, and hence reduces the tendency to cracking , with a corresponding improvement in protective value. Nickel, on the other hand, may be employed to provide a measure of mechanical support, and hence enhanced wear resistance, for a thin rhodium deposit. A nickel undercoating is so used on copper printed connectors, where the thickness of rhodium that may be applied from conventional electrolytes is limited by the tendency of the plating solution to attack the copper/laminate adhesive, and by the lifting effect of internal stress in the rhodium deposit. 

Electrical conductivity must be strictly controlled, as with the submerged electrode boiler, but the limits are higher (normally around =3,500 jLS/cm maximum). 

In practice, control over BW TDS more usually is provided by placing limits on electrical conductivity. 

Measurement of the (limited) dissolved solids present in the BW is normally best achieved by means of electrical conductivity. Clearly, any rise in conductivity indicates that solids are entering with the FW. 

---