Variable-voltage sources

The function of a simple three-electrode system can be understood from Fig. 18b.2a. The variable voltage source, Vs, is placed between the working and the counter electrodes so that the electrochemical reaction can take place on both electrodes at the applied excitation potential. The current response flowing during a redox reaction is monitored by the voltmeter across a standard resistor, Rt. Since we are only interested in... 

Fig. 18b.2. (a) A simple three-electrode system with a variable voltage source, (b) A potentiostat made of three operational amplifiers. 

Voltage followers are used to buffer the output of voltage sources. An unbuffered voltage source is loaded when a load causes current to flow from the source. In Fig. 5(a), a battery and a potentiometer are used to construct a variable voltage source. In the presence of a load resistance, the load parallels a portion of the potentiometer, changing the parallel portion of the potentiometer resistance to Rp = + l)- This causes the... 

A storage oscilloscope with a variable voltage source on the input makes it possible to write any curves on the screen and to store them for subsequent mathematical manipulations. More effort is involved in the scanning of a cut-out template curve or a curve plotted by an electron beam (cathode ray). 

General-purpose stabilized variable-voltage sources. 149... 

The practical circuit in Figure 24-6c shows other components necessary in potentiostalic coulometry. This circuit includes a variable voltage source at the noninverting input of the operational amplifier so that the potentiostat control potential can be varied, a booster amplifier to supply the high currents that are often necessary, and an integrator and readout device. The presence of the booster amplifier has no effect on the potential control circuit. In the circuit, I, = I - I2, but because the input bias current /j of operational amplifier 1 is negligibly small, — /, which passes to the integrator and readout. 

Cartridge Heater Leads to Variable Voltage Source... 

The Volta-potential difference A i/r bet ween the test electrode and the reference electrode is given by the sum of the CPD A[Pg.553]

The simplest variable voltage source is a battery connected across a potentiometer and adjusted manually. The batteries can be replaced by a... 

The vibrating capacitor method is based on the work of Lord Kelvin [1898K] and of Zisman [32Z]. A condensor is formed of the surface to be studied and a reference electrode in front of it which are connected by a ammeter and a variable voltage source. If the capacitance between the plates (sample and reference electrode) is changed, e.g., by changing their distance, a current will flow. By compensating the... 

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