Resistance measurement bridge method

A key factor in the suitabihty of cokes for graphite production is their isotropy as determined by the coefficient of thermal expansion. After the calcined coke was manufactured into graphite, the axial CTE values of the graphite test bars were determined using a capacitance bridge method over a temperature range of 25 to 100°C. The results are summarized in Table 24. Also included in the table are bulk density measurement of calcined cokes and the resistivity values of their graphites. 

The ionic conductivity of a solvent is of critical importance in its selection for an electrochemical application. There are a variety of DC and AC methods available for the measurement of ionic conductivity. In the case of ionic liquids, however, the vast majority of data in the literature have been collected by one of two AC techniques the impedance bridge method or the complex impedance method [40]. Both of these methods employ simple two-electrode cells to measure the impedance of the ionic liquid (Z). This impedance arises from resistive (R) and capacitive contributions (C), and can be described by Equation (3.6-1) ... 

The FITSC method is a general method of investigating the electrical properties of high-resistivity solids via the study of thermal relaxation effects and is an attractive alternative to conventional bridge methods, current-voltage temperature measurements, and so forth. 

Bridge methods are also a standard technique for conductivity measurements. The basic Wheatstone bridge circuit is illustrated in Fig. 18. When the bridge is balanced, i.e. the detector D indicates zero current, then the unknown resistance is given by... 

In the year 1843, Charles Wheatstone, the first Professor of Physics at Ring s College, London, invented one of the most accurate and commonly used methods of measuring resistance. It is known as Wheatstone bridge method. By this method the ratio of two resistances is determined and if the value of one of them is known, the value of the other is obtained (Fig 1.3) shows the circuit diagram of Wheatstone bridge. 

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. 

There is no current standard on resistivity measurements other than British Standard BS 1881 Testing Concrete Part 201 1986 Guide to the use of nondestructive methods of test for hardened concrete. Concrete Society (2004) provides a detailed procedure and a pro forma for recording resistivity measurements. Concrete Bridge Development Group (2002) also gives information and guidance. 

Conductivity measurements on electrolyte solutions are generally carried out with the help of bridge methods, a conductance cell filled with the electrolyte solution being one of the resistances in the arms of an ac Wheatstone bridge. Bridge and cell design is highly developed, and a precision of 0.01% is not unusual. 

The side screens enabled that the distance Lh between the edges of the electrodes and the side walls of the cell to be varied for given values Ah and 2Ch- The resistance of the system for various adjusted values Lh was measured by the bridge method using the platinum electrodes in a 0.020 M KCl solution. The electrodes were 2 cm long and 1 cm wide. The inter-electrode distance was 2 cm. Hence, in this case Ah = Ch- The back sides of the electrodes were insulated. The upper edges of the electrode touch the free surface of the solution and the lower edges of the electrode touch the bottom of the cell. 

One of the oldest instrumental methods for concentration determination is to measure electrolytic conductance. The measurement set-up is simple. It is sufficient to determine the resistance between two inert metalhc electrodes. The well-known Wheatstone bridge can be utilized as with any other resistance measurement (Fig. 5.1). The bridge is balanced, i.e. the variable resistor Rv is adjusted to obtain zero at the instrument included in the circuit. Commonly this is an oscilloscope, since AC amplitudes must be detected. If the scope displays zero, the following condition is valid ... 

Outline of Method and Apparatus.—For the purpose of measuring the resistance of a solution, one usually employs the Wheatstone bridge method, the arrangement of which is shown dia-grammatically in Fig. 53. 

A common known method to get eddy-current informations about material flaws is the measurement of real- and imaginary part of the complex impedance of a coil in absolute circuit. The measurement, shown in this paper, are done with an impedance analyzer (HP4192A). The device measures the serial inductance L, and the serial resistance Rs of the complex impedance with an auto-balance bridge measurement circuit [5]. 

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. 

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