Voltage measurement with spaced reference electrode
First Claim
1. In the measurement of corrosion currents of an Interface Electrode System through measurement of a range of current-potential relationships on a system including a nongaseous ionic conductor in which are immersed a measured electrode, an opposed electrode, and a reference electrode wherein the reference electrode is spaced from said measured electrode, the method of correcting for the sum of the IR voltage drops of ionic conduction between said measured and reference electrodes and of electronic conduction in a lead wire between a measuring device and the measured electrode, comprising the steps of:
- establishing an IR drop across a potentiometer by passing a DC correction current therethrough, said IR drop having a voltage greater than the sum of the IR drops to be corrected for;
maintaining said correction current at a value proportional to a DC polarizing current of said measured current-potential relationship, and in a direction of flow fixed with relation to the direction of flow of said DC polarizing current;
providing one end and an arm of said potentiometer in series with a potential measuring circuit between said measured and reference electrodes, and in polarity to oppose the polarity of said IR drops; and
adjusting the arm of said potentiometer to deliver that value of correction voltage that produces approximately 0.02 volt separations between transition points of line slope change in an X-Y recording of said measured range of current-potential relationships.
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Accused Products
Abstract
Method and device for accurately measuring polarization voltage of a measured electrode with a reference electrode in the form of an electrode in direct contact with the ionic conductor and separated in spacing from said measured electrode. The error of ionic conductor IR drop between measured and reference electrodes is corrected by a voltage of opposed polarity connected in series with said reference electrode, made proportional to the DC current polarizing said measured electrode, and adjusted in value to produce a characteristic 0.020 volt separation between transition points of line slope change in the measured initial range of the polarization current-potential relationship. Calibrating circuitry enables an X-Y recorder to accurately plot the current potential relationship.
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Citations
24 Claims
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1. In the measurement of corrosion currents of an Interface Electrode System through measurement of a range of current-potential relationships on a system including a nongaseous ionic conductor in which are immersed a measured electrode, an opposed electrode, and a reference electrode wherein the reference electrode is spaced from said measured electrode, the method of correcting for the sum of the IR voltage drops of ionic conduction between said measured and reference electrodes and of electronic conduction in a lead wire between a measuring device and the measured electrode, comprising the steps of:
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establishing an IR drop across a potentiometer by passing a DC correction current therethrough, said IR drop having a voltage greater than the sum of the IR drops to be corrected for; maintaining said correction current at a value proportional to a DC polarizing current of said measured current-potential relationship, and in a direction of flow fixed with relation to the direction of flow of said DC polarizing current; providing one end and an arm of said potentiometer in series with a potential measuring circuit between said measured and reference electrodes, and in polarity to oppose the polarity of said IR drops; and adjusting the arm of said potentiometer to deliver that value of correction voltage that produces approximately 0.02 volt separations between transition points of line slope change in an X-Y recording of said measured range of current-potential relationships. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 15, 16)
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10. In apparatus for measuring corrosion currents of an Interface Electrode System through measurement of a range of current-potential relationships on a system including a nongaseous ionic conductor in which are immersed a measured electrode, an opposed electrode, and a reference electrode wherein the reference electrode is spaced from said measured electrode, improvement through means to correct for the sum of IR voltage drops of ionic conduction between said measured and reference electrodes and of electrode conduction in a lead wire between a measuring device and the measured electrode, said apparatus comprising:
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means for establishing an IR drop across a potentiometer by passing a DC correction current therethrough, said IR drop having a voltage greater than the sum of the IR drops to be corrected for; means for maintaining said correction current at a value proportional to a DC polarizing current of said measured current-potential relationship, and in a direction of flow fixed with the relation to the directional flow of said DC polarizing current; one end and an arm of said potentiometer in series with a potential measuring circuit between said measured and reference electrodes, and in polarity to oppose the polarity of said IR drops; and means for adjusting the arm of said potentiometer to deliver that value of correction voltage that produces approximate ly 0.02 volt separations between transition points of line scope change in an X-Y recording of said measured range of current-potential relationships - View Dependent Claims (11, 12, 13, 14, 17, 22, 23, 24)
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18. In a device for measuring corrosion currents of the Interface Electrode System through measurement of initial range of current-potential relationship made on a system including a non-gaseous ionic conductor in which is immersed a measured electrode, an opposed electrode, and a reference electrode in the form of an electrode spaced from said measured electrode the improvement comprising:
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means for DC voltage delivery to said measured and opposed electrodes including a source of variable DC voltage connected across first and second potentiometers; a motor connected to the arm of said first potentiometer through a releasable clutch mechanism and gear train adapted to drive the arm of said first potentiometer across its resistor from positive to negative polarity through a time lapse of about 30 minutes, with the arm of said first potentiometer connected to said measured electrode and the arm of said second potentiometer connected to said opposed electrode; means for polarizing current measurement comprising a microammeter connected in series with the polarizing current, and the X axis input of an X-Y recorder connected across said microammeter; an error correcting potentiometer connected at one end to said measured electrode; means for polarization voltage measurement including one lead from the Y axis input of said X-Y recorder connected to said reference electrode, and the other lead connected through a free electrode potential equalizing circuit to the arm of said error correcting potentiometer; means for passing a correction current through said error correcting potentiometer, proportional to said polarizing current and in direction to oppose the polarization voltage produced on said measured electrode; and whereby the voltage separation between consecutive transition points in the recorded current-potential relationship is made substantially equal to 0.020 volt by the adjusted position of the arm of said error correcting potentiometer. - View Dependent Claims (19, 20, 21)
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Specification