Wheatstone’s bridge

Show that the proportional error involved in the measurement of an electrical resistance on a Wheatstone s bridge is least near the middle of the bridge. Let B denote the resistance, l the length of the bridge, the distance of the telephone from one end.. . y = Bx/(l + x). Proceed as above and show that when (the middle of the bridge), the proportional error is a minimum. 

Ri and R2 are predetermined resistances. These days, Wheatstone s bridge circuit is only used for precision measurements, if at aU. Modem instraments for measuring conductivity work using automatic balancing by a complex electronic circuitry and display the desired resistance directly (or, when appropriately cahbrated, the conductivity). 

Fig. 21.14 Experimental setup (Wheatstone s bridge circuit) for determining the electric resistance of an electrolyte solution.

Wheatstone s bridge hwet- Ston, wet-, chiefly British -stsn- [Sir Charles Wheatstone] (1872) n. If the resistances, ri, t2, r, and T4 form the arms of a Wheatstone s bridge in order as the circuit (omitting cell and galvanometer connections) is traced, when the bridge is balanced... 

In the non-isothermal method the catalytically active sensing element and a similar but catalytically inert element form two arms of a Wheatstone s bridge. Power is supplied to the circuit to heat the elements to their operating temperature, and the values of the fixed resistors selected such that the bridge balances in air. When flammable gas is passed over the elements, reaction takes place on the sensing element, imparting power to the element and thus... 

The isothermal method employs a similar Wheatstone s bridge circuit to the earlier method. However, the compensator is replaced by a fixed resistor, and the voltmeter is replaced by a feedback circuit (17) which governs the electrical power supplied to the catalytic element. In this way the heat liberated during reaction is sensed by the feedback circuit and the electrical power is reduced to maintain the element at a constant temperature. Thus, if P is the electrical power required to maintain the element at... 

Ami S, Hliwa M, Joachim C (2003) Balancing a four-branch-single-molecule nanoscale Wheatstone bridge. Nanotechnology 14 283... 

The method determines the partial pressure of methane in the gas phase above the solution (Henry s law). Methane catalytically oxidizes on a heated platinum filament, that is part of a Wheatstone bridge. The heat generated increases the electrical resistance of the filament which is measured and compared against calibrated standards. 

Nernst applied the electrical bridge invented by Wheatstone to the measurement of the dielectric constants for aqueous electrolytes and different organic fluids. Nemst s approach was soon employed by others for measurement of dielectric properties and the resistance of galvanic cells. Finkelstein applied the technique to the analysis of the dielectric response of oxides. Warburg developed expressions for the impedance response associated with the laws of diffusion, developed almost 50 years earlier by Fick, and introduced the electrical circuit analogue for electrolytic systems in which the capacitance and resistance were functions of frequency. The concept of diffusion impedance was applied by Kruger to the capacitive response of mercury electrodes. ... 

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. 

Although the Nemst method is subject to many minor sources of error Nernst s results on the dielectric constant of liquids are very close to those obtained by later and more precise measurements. The Wheatstone bridge method lias been used by Smyth and associates.6 In principle their bridge is essentially that shown in Fig. 2. However, a vacuum tube oscillator replaces the induction coil, and precision in locating the balance is attained with the aid of vacuum tube amplification. As in precise conductance measurements care must be exercised to avoid errors due to capacity effects between the different arms of the bridge, and to earth. This may be accomplished by appropriately designed electrostatic screening, ... 

Fig. 4.1.12 Thin-film metal structures on the steel membrane of Bosch s high-pressure sensor and the equivalent circuit of a Wheatstone bridge [27]...

The sensor s transducer principle combines a membrane, as a mechanical transducer, with thin-film metal resistors forming a Wheatstone bridge, as an electromechanical transducer. The output voltage of the Wheatstone bridge is given by... 

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