Resistivity method

The electrical-resistance method involves passing an electric current through the structure and exploring the surface with voltage probes. Flaws, cracks, or inclusions will cause a disturbance in the voltage gradient on the surface. Railroads have used this method for many years to locate transverse cracks in rails. 

For a higher ambient temperature, the end temperature of the winding will exceed the permissible limit by the amount the ambient temperature is higher. For example, for a class E motor, an ambient temperature of 30°C will cause the end temperature to reach I25°C as against 115°C permissible by the resistance method. For details refer to Sections 9.1 and I 1.3.2. 

T - by thermometer method (only permissible if the resistance method is not practicable). 

Resistance method - this is the most preferred method for motors up to 5000 kW. 

This method is applicable where neither the embedded temperature detector nor the resistance method is... 

When it is not practical to determine the temperature rise by the resistance method, as in the case of low resistance windings, especially when the resistance of joints and connections form a considerable percentage of the total resistance. 

When, for reasons of mass prodtiction, the thermometer method alone is tised. ttUhongh the resistance method would be possible. 

Testing of metal-enclosed switchgear assemblies 14/435 Insulation resistance method... 

I have decided to use a current transformer to sense the primary current waveform, since resistive methods are impractical in the half-bridge topology. Several transformer manufacturers make current transformers for such a purpose wound on a toroidal core. Coilcraft makes current transformers with 50, 100, and 200 turns on their secondaries. The secondary voltage must be determined in order to have representative current waveforms of the level to work with the control IC. The voltage needed on the output of the current transformer is... 

The resistance method gives an average temperature of the whole winding. Some parts will be hotter than others usually the end turns will be somewhat cooler than parts of the winding in the middle of the iron core. NEMA committee members have been collecting test data on many machines to determine the correlation between temperature measurements by detector and by resistance, and the standards are periodically updated to reflect any of the technology improvements. 

A comparison of resistivity and electromagnetic techniques (resistance versus specific conductance) shows that resistivity surveys are slower because the technique is necessarily limited to measurements at the fixed electrode points, which must be moved for each new survey. Electromagnetic surveys are not limited by fixed points. Also, certain applications of resistivity methods are best suited for sites where the... 

The PDR (Porosity/Distributed Resistance) method for describing the geometry (Patankar and Spalding)... 

Polarisation-resistance method The polarisation-resistance method (see Section 20.1) has been used for determining corrosion rates of metals buried underground. 

An electrical resistance methods which directly measures loss of metal from a probe installed in the corrosive system under study is described in Section 19.3. It is reported that corrosion equivalent to a thickness loss of as little as 2-5 X 10 cm can be detected . This technique is most useful as a means of monitoring steps taken to reduce corrosion, e.g. by inhibitors, or to detect changes in the corrosivity of process streams. Electrical methods of determining corrosion rates are considered subsequently. 

The Schwerdtfeger polarisation break and the polarisation resistance methods have been studied by Jones and Lowe " in relation to their effectiveness in evaluating corrosion rates of buried metals. A Holler bridge circuit was used to remove IR contributions during the measurement of the polarised potential. Jones and Lowe, on the basis of their studies of buried steel and aluminium specimens, concluded that the polarisation resistance was the most useful, and that the polarisation break had the serious limitation that it was difficult to identify the breaks in the curve. 

Danielson, M. J., Analysis of Errors in Using The Two Electrode and Three Electrode Polarisation Resistance Methods In Measuring Corrosion Rates , Corrosion, 36, No. 4, 174-178, April (1980)... 

The foam detector based on the resistance method acts on the conductivity of the probe. The length of the probe is coated with some electrically insulating material, leaving the tip... 

There is often a particular concern for the effects of outliers or heavy-tailed distributions when using standard statistical techniques. To address this type of a situation, a parametric approach would be to use ML estimation assuming a heavy-tailed distribution (perhaps a Student t distribution with few degrees of freedom). However, simple ad hoc methods such as trimmed means may be useful. There is a large statistical literature on robust and outlier-resistant methods, (e.g., Hoaglin et al. 1983 Barnett and Lewis 1994). 

It is a well-known and a widely recognized fact that the electrical resistance of palladium is a function of its hydrogen content. In [118], some problems on the resistance method regarding the in situ measurement of hydrogen content is discussed. 

Cembrola56 has compared microscope, stylus and resistivity methods and concludes that no one method is universally the best. Guerbe and Freakley57 compared four methods including a microwave energy absorption method. 

Despite its title, ASTM D99119 is a resistivity method for sheet rubber material, not for products. It specifies the four electrode method and, hence, is similar to ISO 1853 and BS 2040, method 2, but the electrode construction is different and care would need to be taken to avoid leakage between the current and potentiometric electrodes. 

Gilespie. S.H. Antibiotic Resistance Methods and Protocols, Humana Press, Torowa. NJ. 2000. 

Strain Gages. Essentially, they are based on electrical measurements of strains produced by the action of stress. There are several ways for measuring strains, but the most convenient is the resistance method. The apparatus used for these measurements, known as "resistance manometer , depends upon the change in resistance of a metal (such as platinum, manganin or mercury) when subjected to pressure. The change in resistance is usually measured by means of a very sensitive Wheatstone bridge, but it may also be measured by a potentiometer or by an... 

There are various surface techniques, eg., optical interferometry high frequency capacitance and resistance method, which demonstrate the build up of the physically and chemically reacted film during boundary lubrication in scuffing reactions (Anghel et al., 1997 Dowson et al., 1996 Smalley and Cameron, 1996). 

One technique is referred to as the "spreading resistance" method. In this procedure, a wafer is fractured and the edge containing the film is beveled, as shown in Figure 15. Then, a two-point probe is used to measure resistivity at a sequence of points traversing the interface between the substrate and the epi film. By relating the local resistivity to carrier concentration, one is able to deduce the concentration of dopant atoms over the epi layer. This technique is effective for even highly-doped layers. 

The corrosion current density icoa is evaluated by the electrochemical polarization resistance method assuming that both the anodic and the cathodic partial currents obey the Tafel relation ... 

Resistivity. The resistivity method measures the electrical resistivity of the geohydrologic section, which includes soil, rock, and ground water. Interpretation of these measurements provide information on layering and depths of subsurface horizons as well as lateral changes in the... 

Electromagnetics (EM). Electromagnetics (EM) measurements provide similar data as obtained using the resistivity method these data are called ground conductivities (or reciprocal resistivities). Some of the newer EM techniques are portable, permitting data to be gathered as fast as a man can walk. Therefore, the EM method has an advantage over the older resistivity method in that subsurface conductivities (reciprocal resistivities) can be collected rapidly and continuously as the operator and instrument move across the land surface. 

The Polarization Resistance Method for Determination of Instantaneous Corrosion Rates... 

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