pH and concentration meter

• US 5,198,093 A
• Filed: 01/17/1992
• Issued: 03/30/1993
• Est. Priority Date: 05/10/1990
• Status: Expired due to Fees

• Current Assignee: Continental Bank NA
• Original Assignee: Orion Research, Inc. (Thermo Fisher Scientific Incorporated)
• Inventors: West, Steven, Barbookles, James, Somes, Loren, McIntre, Christopher, Shyr, Chin-I, Cohen, Jeffrey S., Paquette, Thomas, Sydlowski, Paul, Brockway, Laura
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US07/803,326
• Time in Patent Office: 438 Days
• Field of Search: 204/406, 204/407, 204/433, 204/416
• US Class Current: 204/406
• CPC Class Codes: G01N 27/4165 for pH meters

Abstract

The present invention comprises an electrochemical metering apparatus that provides for convenient storage and presentation of the analytical electrode, simple assembly, and two calibration modes. The apparatus includes an electrode storage and presentation assembly that permits the user to introduce the electrode into a sample solution while simultaneously observing the meter'"'"'s output, and store the electrode when not in use. All structural components are intended to fit together with interlocking tabs and windows. A serial port fits within the construction of the main housing without the need for bolts, and battery clips that depend directly from the circuit board obviate the need for wiring connections. The present invention also features two calibration modes. A "segment addition" mode permits separation of the voltage/concentration curve into individually plotted regions, the number of which depends on the number of reference solutions used in the calibration procedure. The segment corresponding most closely to the measured potential of a sample solution is used to calculate concentration. In an alternative calibration mode, one or more reference solutions are used to establish metered voltage/concentration combinations that are compared with expected, known values. Any discrepancies therebetween furnish a "noise level" value associated with the apparatus that can be used to more precisely define the orientation of the voltage/concentration curve.

Claims

1. Apparatus for measuring the equivalent ion concentration of a sample solution, comprising:

a. an electrode means that responds to a potential difference representative of the concentration of ionic species in solution;

b. a display means;

c. memory means to store sets of values, each set comprising a known equivalent ion concentration and a measured potential difference at such concentration;

d. processor means to calculate a baseline standard cell potential from each of these sets of values according to the Nernst equation; and

e. input means to receive electrode signals representative of the potential difference of a sample solution and to transfer the signals to the processor means for calculation of the equivalent ion concentration of the solution and display thereof on the display means,

wherein the processor means comprises means to calculate the equivalent ion concentration based on the baseline standard cell potential associated with the measured potential difference that is closest to the potential difference of the sample solution.

2. Apparatus for calibrating an electrochemical metering apparatus that includes display means and means for receiving signals generated by an electrode means that responds to a potential difference and calculating therefrom a value for the concentration of ionic species in solution according to the Nernst equation, the calibration apparatus comprising:

a. memory means to store sets of values, each set comprising a known equivalent ion concentration and a measured potentials difference at such concentration; and

b. processor means including;

1) means to calculate a baseline standard cell potential for each of these sets of values;

2) means to compute differences among the calculated baseline potentials;

3) means to calculate a correction value which, when added to the known equivalent ion concentrations to produce adjusted ion concentrations, minimizes differences among the baseline potentials associated with the adjusted ion concentrations; and

4) means to store the correction value in the memory means for use in calculating equivalent ion concentrations according to the Nernst equation.

3. Apparatus for measuring the equivalent ion concentration of a sample solution, comprising:

a. an electrode means that responds to a potential difference representative of the concentration of ionic species in solution;

b. a display means;

c. memory means to store sets of values, each set comprising a known equivalent ion concentration and a measured potential difference at such concentration;

d. processor means comprising means to calculate equivalent ion concentrations based on measured potential differences according to the Nernst equation;

e. input means to receive electrode signals representative of the potential difference of a sample solution and to transfer the signals to the processor means for calculation of the equivalent ion concentration of the solution according to the Nernst equation, and display thereof on the display means; and

f. calibration means for deriving a correction value for use by the processor means in solving the Nernst equation, the calibration means including;

1) means to calculate a baseline standard cell potential for each of the sets of values stored in the memory means;

2) means to compute differences among the calculated baseline potentials; and

3) means to calculate a correction value which, when added to the known equivalent ion concentrations to produce adjusted ion concentrations, minimizes differences among the baseline potentials associated with the adjusted ion concentrations.