Abstract: Apparatus for measuring electrolyute concentrations in fluid samples. The apparatus includes an ion selective electrode having a plurality of ion selective detection sites. Each site has an affinity for a preselected electrolyte of interest and generates a potential having a magnitude related to the concentration of the corresponding electrolyte in the sample. A voltage to optical transducer circuit is provided to convert the voltage differentials to optical signals having intensity related to the concentration of the electrolytes in a first embodiment, a digital code related to the concentration of the electrolytes in a second embodiment, and an optical absorption or density value related to the concentration of the electrolytes in a third embodiment. The optical signals are suitable for detection by conventional optical detector apparatus of assay instruments and may be processed using conventional two point linear interpolation techniques to determine the concentrations of the preselected electrolytes.

Abstract: Methods and apparatus are provided for sensing gases in the environment wherein electrochemical sensing procedures are utilized not only for monitoring ambient continuously for the presence of such gases; but also, for the periodic automatic recalibration and self-adjustment of the sensing instrument, as required, to accommodate changing conditions with time. Such accommodation includes not only changes in the instrument itself, but also changes in the environment affecting the accuracy of the monitoring function. The instrument is connected with a microprocessor, or other information storage or retrieval instrumentation which controls the periodic recalibration by measuring, separately from the monitoring function, the electrochemical response to a sample of the gas being monitored, and by adjusting the subsequent instrument readings to reflect the recalibration. During this recalibration procedure, the instrument can be adjusted to zero reading for accommodating drift, as will be understood.

Abstract: A wick system for an electrochemical cell is provided to assure the connection between the electrodes of the cell. The wick system of the invention absorbs electrolyte and by capillary action provides a continuous electrolyte path between the electrodes. The wick may be in the form of a substantially flat piece extending in one plane for those cells having all electrodes positioned at one end thereof. Alternatively, the wick may be substantially tubular to extend from one end of a cylindrical electrolyte containing chamber to another, for a cell having electrodes positioned at each end thereof. Additionally, the wick may extend from one end of the cell to the other in a folded bellows-like form. In any of the forms, the wick system allows for a continuous operation of the cell, even with reduced electrolyte content, and regardless of the three-dimensional orientation of the cell, by absorbing electrolyte and maintaining electrolytic contact.