Measurement of polarographic current
First Claim
1. In a polarographic cell of the type wherein the electrodes are continuously washed by a buffer solution, and wherein an electrical cell current is generated by the oxidation of hydrogen peroxide carried by the buffer solution past said electrodes, the improvement in measuring said cell current which comprises:
- means for converting said cell current to an equivalent cell signal voltage;
control means, connected to said cell signal voltage, for electronically generating a first signal when said cell signal voltage is below a pre-selected rate of change and a second signal when said cell signal voltage is above said pre-selected rate of change;
means, connected to said cell signal voltage and said control means, for electronically holding and passing a constant voltage signal, equal in magnitude to the value of said cell signal voltage at the time said second signal is generated, in response to said second signal;
peak detector means, connected to said cell signal voltage and said control means, for holding and passing as a constant voltage signal the maximum value reached by said cell signal voltage, said peak detector means being responsive to said second signal to release any previous peak value held therein; and
subtraction means for electronically subtracting said voltage signal equal in magnitude to the value of said cell signal voltage at the time said second signal is generated from said voltage signal representing the maximum value reached by said cell signal voltage and furnishing a voltage signal equal to the difference thereof.
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Accused Products
Abstract
Apparatus and method for the measurement of a cell current. A polarographic cell, which may be a two or three electrode system, furnishes a cell current which is a measure of a particular constituent of a material under test in the cell. The electrodes are continuously washed by a buffer solution which gives a base line or steady state current. The current from the cell is converted to a voltage for ease of measurement. The first derivative with respect to time is taken of the voltage. When this rate of change of voltage exceeds a pre-selected level, a signal is generated. This signal causes a sample and hold unit to hold and present as a constant output the voltage level at that time. This is the steady state value. The signal also resets a peak detector which accepts the cell voltage and tracks its value until a maximum is reached. Then, the maximum value is held as a constant output quantity. An electronic difference amplifier subtracts the steady state voltage from the maximum detected voltage to give a value of voltage representing the true peak level.
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Citations
12 Claims
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1. In a polarographic cell of the type wherein the electrodes are continuously washed by a buffer solution, and wherein an electrical cell current is generated by the oxidation of hydrogen peroxide carried by the buffer solution past said electrodes, the improvement in measuring said cell current which comprises:
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means for converting said cell current to an equivalent cell signal voltage; control means, connected to said cell signal voltage, for electronically generating a first signal when said cell signal voltage is below a pre-selected rate of change and a second signal when said cell signal voltage is above said pre-selected rate of change; means, connected to said cell signal voltage and said control means, for electronically holding and passing a constant voltage signal, equal in magnitude to the value of said cell signal voltage at the time said second signal is generated, in response to said second signal; peak detector means, connected to said cell signal voltage and said control means, for holding and passing as a constant voltage signal the maximum value reached by said cell signal voltage, said peak detector means being responsive to said second signal to release any previous peak value held therein; and subtraction means for electronically subtracting said voltage signal equal in magnitude to the value of said cell signal voltage at the time said second signal is generated from said voltage signal representing the maximum value reached by said cell signal voltage and furnishing a voltage signal equal to the difference thereof. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a method of measuring biological fluids wherein a polarographic cell is continuously washed by a buffer solution and wherein an electrical cell current is generated by the oxidation of hydrogen peroxide carried by the buffer solution past the cell electrodes, an improved method of measuring said cell current which comprises the steps of:
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electronically converting said cell current to an equivalent cell signal voltage; electronically generating a signal quantity representing the time rate of change of said cell signal voltage; electronically generating a first signal when said time rate of change is less than a pre-selected value; electronically generating a second signal when said time rate of change is greater than said pre-selected value; electronically holding and passing as a constant voltage signal the value of said cell signal voltage present at the time of generation of said second signal; electronically measuring and holding the maximum value reached by said cell signal voltage; and electronically subtracting said constant voltage signal from said maximum value of said cell signal voltage to thereby generate a difference voltage. - View Dependent Claims (10, 11, 12)
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Specification