Computerized device for pulsed potential voltammetric measurement of oxygen using a membrance covered polarographic electrode

• US 4,556,472 A
• Filed: 06/27/1984
• Issued: 12/03/1985
• Est. Priority Date: 04/19/1982
• Status: Expired due to Term

• Current Assignee: Providence Plantations, Rhode Island Board of education (STATE OF RHODE ISLAND)
• Original Assignee: Board of Governors For Higher Education State of, Providence Plantations
• Inventors: Langdon, Christopher
• Primary Examiner(s): Metz, Andrew H.
• Assistant Examiner(s): Chapman, Terryence
• Application Number:
  US06/625,134
• Time in Patent Office: 524 Days
• Field of Search: 204/1 T, 204/400, 204/406, 204/415
• US Class Current: 204/406
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors

Abstract

An oxygen analyzer which measures the level of dissolved oxygen in a liquid stream. The measuring process embodies chronoamperoemetry of pulsed potential voltammetry. The signal from the electrode is real time averaged. The analyzer does not require temperature, salinity or pressure compensation circuitry and does not have to be calibrated repeatedly.

Claims

1. An apparatus for determining the level of oxygen in a fluid stream which comprises:

(a) means to place an electrode in electrolytic communication with a fluid stream containing oxygen;

(b) means to energize the electrode for a first duration of time (d) and to prevent energization of the electrode for an interval of time (i), which interval of time (i) is longer than the duration time (d), the electrode providing a first signal corresponding to the oxygen to be measured derived from time (d);

(c) means to sample repeatedly over at least one cycle of the predominant noise frequency the first signal generated from the electrode which signal corresponds to time (d), the first signal sampled at a rate over at least the one cycle of the predominant noise frequency such that the sampled signal when averaged provides a signal substantially free of drift;

(d) means to average the signals so sampled;

(e) means to store the signals so averaged;

(f) means to provide a second signal corresponding to the salinity of the fluid stream;

(g) means to input the value of the salinity into the apparatus;

(h) means to calculate salinity correction factors;

(i) means to apply the salinity corection factors to stored averaged signals to produce data corresponding to the level of the oxygen in the fluid stream being measured; and

(j) computer means to control the energization of the electrode; and

the sampling, averaging and storing of the signals; and

the calculation of the salinity correction factors and the application of the correction factors to the averaged signals.

2. The apparatus of claim 1 which includes means to calculate and means to display the time rate of change of oxygen concentration using linear regression analysis.

3. The apparatus of claim 1 wherein the measns to energize the electrode includes means to apply a polarizing voltage to the electrode.

4. The apparatus of claim 1 which includes means to display the level of the oxygen in the fluid stream.

5. The apparatus of claims 1 or 4 wherein the means to average the signal so taken includes means to average the signal over at least two cycles of the predominant noise frequency.

6. The apparatus of claim 1 which includes:

means to provide a third signal which corresponds to the temperature of the fluid stream;

means to calculate temperature correction factors;

means to apply the temperature correction factor to the stored signals and wherein the computer means includes means to calculate the temperature correction factors and to apply said correction factors to the averaged signals.

7. The apparatus of claim 6 which includes:

means to calculate the temperature correction factors using nonlinear equations.

8. The apparatus of claim 6 which includes means to alternately select for sampling both the first and the third signals.

9. The apparatus of claim 8 which includes means to display simultaneously the level of the oxygen in the fluid stream and the temperature of the fluid stream.