The Foxboro Company

Kenneth S Fletcher, Iii

Raymond Annino

Jay M Weiner

Maynard C Cheney

William E Earle

A gas chromatograph for measuring the amounts of selected sample gas components such as oxygen and carbon monoxide. The system comprises a high-temperature (600.degree. C.) zirconia cell detector supplied on one side with a continuous stream of oxygen flowing at a constant rate. A voltage source connected to the zirconia cell transports all of this oxygen to the other side of the cell, resulting in a constant background cell current. Sample components from the chromatographic column are injected sequentially into the oxygen stream. When oxygen is injected the cell current increases due to the increase in total oxygen available for transport through the cell. When carbon monoxide is injected, it is fully combusted with the oxygen, and the current correspondingly decreases due to reduction of the oxygen available for transport. The deviation in cell current with reference to the background current is integrated for each component to produce output signals indicating the amount of the component.

Apparatus and method for determining the amount of a sample gas component

An ion-sensitive electrode, usable for measuring the activity or concentration of a predetermined ion in a fluid stream of an industrial process, includes a vessel partially filled with an electrolyte and fabricated with one wall portion thereof comprising a rigid, porous fritted back-up element and a relatively thin, ion-sensitive, non-porous membrane. Being preferably made of the same ion-sensitive material as the membrane, the back-up element is produced using a sintering process which results in a porous solid having maze-like passages extending randomly therethrough in all directions. One surface of the back-up element is fused to and supports a thin layer of ion-sensitive material that has been applied to the back-up element, heated to its molten working temperature and then cooled to form the non-porous membrane. Located within the vessel, the back-up element also serves to transport the electrolyte through its passages for wetting the interior surface of the thin membrane fused to the back-up element. The exterior surface of the membrane is in contact with the fluid stream so that an electrical potential responsive to the activity or concentration of the pre-determined ion can be developed across the membrane.

Ruggedized ion-responsive electrode and its manufacturing process

An amperometric analysis system and method includes a flow tube constituting the amperometric cell in which magnetic flow metering electrodes function also as the counter and test electrodes for amperometric measurement. By combining the magnetic flow measurement with the amperometric measurement, additional electrodes are not needed to obtain the flow signal for compensating the amperometric measurement. Ultrasonic drivers are mounted on the end of the shank of the counter and test electrodes and driven by an ultrasonic oscillator to activate the electrodes to keep them clean. Complementary cleaning can be obtained through the simultaneous application of an electrochemical anodic pulse. The system includes a three-electrode circuit potentiostat in which the potential of the test electrode is fixed versus a reference electrode and the current flows between the test electrode and the counter electrode. An isolated current source allows the magnetic flow metering electrodes to serve simultaneously as test and counter electrodes in the amperometric circuit. The flow tube also includes a thermistor temperature compensator. Reliable direct amperometric analysis of a flowing stream is made possible by the invention.

On-line amperometric analysis system and method incorporating automatic

An automatic titration system and method in which the titrant is generated electrolytically and a two-position slider type ceramic sample valve, reliably, accurately and repetitively obtains a volumetric sample from a process loop and introduces it to a titration cell containing a generator or working compartment and an auxiliary compartment separated by a porous frit. The system also includes a two-position slider type ceramic reagent valve for introducing reagent into the titration cell. Titrant created at a generator electrode surface is dispersed into the bulk of the solution by a magnetically coupled impeller in the working compartment which mixes and also pumps the contents of the cell through the reagent and sample valves in a closed loop. Generator and auxiliary electrodes are connected to a current source which provides the electrolysis current. The progress of the titration is monitored by indicating and reference electrodes in the titration cell connected to an appropriate endpoint indicator, output of which is compared to a known setpoint corresponding to the titration endpoint. The total charge delivered to the generator and auxiliary electrodes during titration is measured by a timer or integrator and read out as a trend output signal. The automatic titration system and method of this invention advantageously lends itself to microprocessor control over the titration reaction and titrator sequencing.

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Norfolk, MA, United States of America

Kenneth S Fletcher, Iii