Electrometers reduction

Historically, the first and most important capacitance method is the vibrating capacitor approach implemented by Lord Kelvin in 1897. In this technique (now called the Kelvin probe), the reference plate moves relative to the sample surface at some constant frequency and tlie capacitance changes as tlie interelectrode separation changes. An AC current thus flows in the external circuit. Upon reduction of the electric field to zero, the AC current is also reduced to zero. Originally, Kelvin detected the zero point manually using his quadrant electrometer. Nowadays, there are many elegant and sensitive versions of this technique. A piezoceramic foil can be used to vibrate the reference plate. To minimize noise and maximize sensitivity, a phase-locked... 

The Plasma Chromatograph (PC, registered trademark of the Franklin GNO Corp.) is also an instrument which does not depend on the use of magnetic fields (33). It should be well suited for the study of macroions because (a) the currents measured are well within the range of a Faraday cage-vibrating-reed electrometer detector system, and (b) the instrument operates at atmospheric pressure, thus making unnecessary the reduction in pressure from that of the electrospray chamber. 

Any study of an electrochemical system should be started with the equilibrium mode. In such a mode, the electrodes should not be called the cathode or the anode, and both half-reactions should be shown as reduction reactions. It is because, by common convention, the reference data on the (standard) electrode potentials are given for the reduction reactions. The convention will be discussed in Chapter 4. However, one electrode of an electrochemical cell should be more positive than another one, and the polarity can be experimentally found using the high-resistance electrometer. Also, the polarity of the electrodes in the equilibrium cell can theoretically be calculated using thermodynamic data. This will also be discussed in Chapter 4. 

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