Bipolar digipotentiogrator for electroanalytical uses.  Direct conversion of charge to a digital number

Goldsworthy, William W.; Clem, Ray G.

doi:10.1021/ac60316a013

Cited by 20 publications

(9 citation statements)

References 14 publications

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“…With the interrupter method [36][37][38][39][40][41][42][43][44][45][46][47][48] the polarization current is interrupted periodically for short times within the microsecond range. In these interrupter periods t 0 the ohmic voltage drop iR u disappears immediately, while the "true" polarization voltage E p of the working electrode only decreases slowly due to the storage capacity of the double layer C dl .…”

Section: Current Interrupt Methodsmentioning

confidence: 99%

The iR drop - well-known but often underestimated in electrochemical polarization measurements and corrosion testing

Oelßner¹,

Berthold

Guth

2006

Materials and Corrosion

107

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At first sight the problem of the iR drop and its compensation in electrochemical polarization measurements seems to have only minor significance, but it has actually troubled electrochemists and corrosion scientists for more than a hundred years. For reducing the iR drop in the electrochemical cell, its computation, experimental determination and numerical or automatic electronic compensation numerous scientific and experimental work has been carried out and appropriate suggestions were submitted. These efforts led to commercially available potentiostats with sophisticated facilities for automatic iR compensation. Nevertheless, to date these possibilities have been utilized with a certain hesitancy. Many users underestimate the iR drop, regarding it often merely as a marginal problem, which only has to be taken into account in experiments with very high currents or extremely low conductivity of the electrolyte. Furthermore, there are also doubts and prejudices regarding modern methods of iR compensation, resulting from previous unpleasant experiences or reports on failed experiments with inappropriate equipment or imperfect methods. Reduction or automatic compensation of the iR drop is necessary more frequently than generally assumed and also in most cases possible. On the other hand the application of the different methods is still not completely uncomplicated and requires special experimental experience and care. The aim of the present work is it therefore to give a comprehensive retrospective overview of the ohmic drop problem and the relevant activities to overcome it.

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Section: Current Interrupt Methodsmentioning

confidence: 99%

The iR drop - well-known but often underestimated in electrochemical polarization measurements and corrosion testing

Oelßner¹,

Berthold

Guth

2006

Materials and Corrosion

107

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“…In use of electronic methods, careful design of the potentiostat is very helpful. The current interruption potentiostat (6)(7)(8)(9) and the digital potentiostat (10) were designed so that the sensing of the potential between the working electrode and reference electrode is accomplished when no current passes through the electrochemical cell. The potential control is thus free of iR error.…”

Section: Glossary A¡"mentioning

confidence: 99%

Intelligent, automatic compensation of solution resistance

He¹,

Faulkner²

1986

Anal. Chem.

104

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“…The difference between these two values of current is electronically stored (using sample-and-hold circuitry) and presented to a suitable readout device. The majority of the charging current is effectively subtracted out, although a small concentration independent dc component remains (8).…”

Section: Theorymentioning

confidence: 99%

“…1-61, where the feedback control is still accomplished by means of an analog potentiostat, DDC of the electrode potential is a concept in which the control action is generated by means of a computational algorithm within the computer. This approach is also different from the type of digital control described by Goldsworthy and Clem (7, 8) and White (9), in which the control is effected through measurement of the electrode potential by means of a differential comparator, followed by a digital output. In their technique, which does not involve the use of a computer, the control action and its characteristics are fixed in hardware.…”

mentioning

confidence: 96%

Application of direct digital control of electrode potential to controlled-potential electrolysis experiments

Pomernacki¹,

Harrar²

1975

Anal. Chem.

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A mlnlcomputer program and electronlc hardware have been developed for controlllng the potentlal of an electrode through the medlum of an algorlthm wlthln the computer. The control algorlthm found to be satlsfactory Is the dlscrete equlvalent of proportlonal-plus-Integral actlon. Control func= tlone are carrled out In assembly language at a sampllng rate of 1 kHz; the parameters that govern the control actlon and electrolysls condltlons can easlly be changed on-llne vla a hlgh-level conversatlonal language. Theory has been developed for guidance In tunlng the controller for varlous electrolysls cell characterlstlcs. Detalled control obJectlves and speclflcatlons have been formulated for typical electrolysls experlments. The system has been tested wlth mercury-pool and platlnum worklng-electrode cells, demonstratlng that the control objectives can be met and that the theory Is useful. System rlsetlmes of lese than 8 msec can be achleved, and steady-state control errors are not slgnlflcant. A malor fractlon of the tlme durlng each sampllng perlod ls available for other data processlng.The direct digital control (DDC) of the potential of the working electrode in a 3-electrode cell has been viewed as an interesting possibility (1, 2 ) ever since the advent of minicomputers. In contrast to computer-controlled potentiostats (see, for example, Refs. 1-61, where the feedback control is still accomplished by means of an analog potentiostat, DDC of the electrode potential is a concept in which the control action is generated by means of a computational algorithm within the computer. This approach is also different from the type of digital control described by Goldsworthy and Clem (7, 8) and White (9), in which the control is effected through measurement of the electrode potential by means of a differential comparator, followed by a digital output. In their technique, which does not involve the use of a computer, the control action and its characteristics are fixed in hardware.Direct digital control via software has been widely implemented in industrial process control (10-121, but for a number of reasons has not yet found application in electrochemistry. One reason has been that a speed of response comparable to that of analog circuitry could not be attained because of computational speed limitations in the computer. Now, however, the existence of faster minicomputers, digital multiply/divide circuits, and advanced software techniques have enabled significantly faster data processing. At the present time, DDC would appear to be practical at least for laboratory-scale controlled-potential electrolysis, and possibly analytical voltammetry, because these techniques do not require very high control speeds.A second factor hindering the development of DDC in the laboratory has been the much greater cost of the digiAuthor to whom correspondence should be addressed.tal, compared to the analog approach. However, when the ubiquity and versatility of the minicomputer is considered, the use of DDC can be regarded much more favorably. ...

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Bipolar digipotentiogrator for electroanalytical uses. Direct conversion of charge to a digital number

Abstract: A bipolar digital potentiostat based upon the principle of charge injection or extraction has been built, tested and applied to polarographic and anodic stripping analyses. It is capable of o. 01% precision.

Cited by 20 publications

References 14 publications

The iR drop - well-known but often underestimated in electrochemical polarization measurements and corrosion testing

The iR drop - well-known but often underestimated in electrochemical polarization measurements and corrosion testing

Intelligent, automatic compensation of solution resistance

Application of direct digital control of electrode potential to controlled-potential electrolysis experiments

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