Resistance measurement potentiometric method

Samples were deformed by rolling at room temperature after disordering and quenching (40% and 80% reduction in thickness) and after ordering by a 19h annealing at 300°C (30% reduction). Completely recrystallized samples were prepared by annealing 48h at 600°C. Resistivity measurement was done by the potentiometric method in liquid N2 relative to a dummy specimen (accuracy 3x10" ). 

Measurement of R, can be made with a Wheatstone bridge or with a potentiometric method. A three-terminal bridge configuration is shown in Fig. 4, where leads a, b, A, B have resistance R, Rb, Ra> Rb- Since the two fixed resistance arms have been chosen to have the same values the balance condition is simply... 

Several of the procedures described in the previous sections can be advantageously carried out with double barrel tips. Such a probe consists of two capillaries (see Sec. V.B), one of which acts as the potentiometric sensor, while the other is used to determine the tip-substrate distance. For example (79), a gallium microdisk was combined with an ion-selective (K+) potentiometric probe to image K+ activity near the aperture of a capillary (see Fig. 7). Similarly (77), a double barrel tip with one channel as an open Ag/ AgCl micropipette for solution resistance measurement and the other channel as an ion-selective neutral carrier-based microelectrode for potentiometric measurements was successfully used to image concentration distributions for NH4 (Fig. 8) and Zn2+ (Fig. 9). While dual-channel tips facilitate the approach of the substrate and permit a direct determination of the absolute tip-substrate distance, their difficult fabrication severely limits their use. Reference 80 compares the above methods. 

Resistance Measurement. The common methods of resistance measurement in resistance thermometry are the bridge method and the potentiometric method. Basically, the bridge method uses the resistance sensor together with a variable resistor and two fixed resistors to form the four legs of a conventional Wheatstone bridge circuit. On the other hand, the potentiometric method, also called a half bridge, connects the resistance sensor in series with a known resistor. 

Resistivity measurements are done on meander shaped samples by the standard potentiometric method in a stirred bath of liquid nitrogen relative to a dummy specimen For this procedure of residual re istometry the ultra-high measuring accuracy of 3.10 results below 300°C and of 3.10 for annealing treatments at higher temperatures. 

Potentiometry is a powerful electrochemical method when the OCP is measured using a high-resistance electrometer. This method is a common tool for studying equilibrium systems in electrochemical science and engineering. In noneqnilibrium stndies, OCP measurement is nsnally the first step to find out if the cell of interest works properly. Note that dnring the potentiometric measurements, due to the absence of cnrrent in the circuit, any undesirable potential drops inside the phases are absent. In noneqnilibrinm electrochemical systan, the potential drop between working and reference electrodes (called IR drop) is a serious issue to be taken into account experimentally and/or theoretically. 

The international standard for measurement of resistivity of rubbers is ISO 185317 which details one procedure only, the potentiometric or four electrode method. The principle of the method is shown in Figure 13.2 the strip test piece has metal current electrodes clamped at each end and is... 

Conductivity, Electrical Conductometry and Conductometric Titrations. Electrical conductivity is thequality or ability of a substance to transmit electrical energy. If it deals with the conductivity of an electrolyte in solution, it is then called electrolytic conductivity. Conductometry deals with analyses by measuring electrolytic conductivity, based on the fact that ionic substances in many solvents conduct electricity. Conductometric titrations are quantative analysis based on the fact that with the addn of the titrating agent to a soln being titrated, the specific conductivity (reciprocal of specific resistance in mhos) changes at a different rate before and after the end point (Comp with Potentiometric Analysis) Refs 1 )Kirk Othmer 4 (L 949), 325-33 (Conductometry) 2)W.G.Berl, Edit, "Physical Methods... 

Electrochemistry works using the principles of oxidation-reduction reactions which generate electric currents or, more simply, the conversion of chemical information into an electrical signal. Electrochemical cells or sensors usually contain a working electrode, to which a potential is applied, and a reference electrode. The oxidation-reduction reaction that ensues is then recorded as an electric current which is a measurement of the analyte from the reaction. Electrochemical methods can be further subdivided into amperometric (measures current), potentiometric (measures potential), conductometric (measures the conductive properties of the medium), impedimetric (measures resistance and reactance) or field effect (measures current through charge accumulation at a gate electrode). ... 

---