Electrochemical Sensor Self-Testing via In-Situ Oxygen Generation
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Solution Overview
Problem
Existing electrochemical sensors for measuring oxygen partial pressure in process fluids face challenges in functional testing, particularly at low oxygen concentrations, where distinguishing between sensor defects and low oxygen levels is difficult, and require additional costly gas generators for testing.
Innovation Solution
A test voltage source is applied between the cathode and guard electrode to produce test oxygen, allowing for functional testing without a separate gas generator, utilizing the reversal of the polarographic principle to increase sensor current for evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate gas generator is used to produce testing gas for sensor function checks, then the sensor can be reliably tested, but the device complexity and cost increase
Solution Approach 1:
The patent combines the gas generator functionality with the sensor body itself. The sensor body is equipped with a gas generator that produces testing gas in situ, eliminating the need for separate external gas generation equipment. This merging of functions allows the sensor to perform self-diagnosis while reducing overall device complexity and cost.
Solution Approach 2:
The sensor performs its own functional testing by generating testing gas internally through the integrated gas generator. The sensor body uses its own components (electrolyte, electrodes) to produce oxygen for testing, enabling autonomous self-diagnosis without requiring external testing equipment or removal from the measuring medium.
2Reliability
If the sensor is removed or complex devices are used to separate the sensor for charging with testing gas, then the sensor can be tested, but the ease of operation deteriorates
Solution Approach 1:
The sensor performs its own functional testing in place within the process fluid. The integrated gas generator produces testing gas that charges the sensor body directly where it is installed, eliminating the need for removal or complex separation devices. This self-service capability significantly improves ease of operation while maintaining testing reliability.
3Quantity of substance
If electrochemical sensors with low oxygen concentration are used, then the measurement range is improved, but the measurement precision deteriorates due to very low measurement current
Solution Approach 1:
The gas generator performs preliminary action by generating oxygen within the sensor body before the actual measurement takes place. This pre-generated oxygen creates a measurable current signal even when the ambient oxygen concentration is very low, enabling the sensor to operate in low-oxygen environments while maintaining sufficient measurement precision through the added test signal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables regular, cost-effective functional testing of electrochemical sensors with minimal measurement interruption, eliminating the need for expensive apparatus and complex switching procedures.
Implementation Method 1
a test voltage source which can be switched in a testing mode between the cathode and guard electrode is provided which produces test oxygen in the process fluid between the cathode and guard electrode for testing the function of the sensor
Implementation Method 2
The reduction of the oxygen at the cathode causes a current flow from the cathode to the anode which is proportional to the oxygen partial pressure
Implementation Method 3
an oxygen-permeable membrane, in order to prevent the exchange of the electrolyte with the measuring medium and other impurities
Data Source
AI summary
An electrochemical sensor for measuring the oxygen partial pressure in a process fluid, comprisesan electrolyte-filled sensor body, which is covered on one side charged with the process fluid by an oxygen-permeable membrane,a cathode on the membrane,an annular guard electrode surrounding the cathode, which in measuring operation lies at the same potential as the cathode,an anode charged by the electrolyte in the sensor body,a reference electrode charged by the electrolyte in the sensor body, wherein between the anode and cathode a voltage can be applied, which is controlled between the cathode (8) and reference electrode at a constant polarization voltage and the measuring sensor current flowing in measuring operation between the cathode and anode is a measure for the oxygen partial pressure in the process fluid, anda test voltage source which can be switched in a testing mode between the cathode and guard electrode for producing test oxygen in the electrolyte and/or in the process fluid between the cathode and guard electrode for testing the function of the sensor.