Corrosion Protected Measuring Electrodes in Electromagnetic Flowmeters
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Solution Overview
Problem
Electromagnetic flowmeters face challenges in corrosion resistance of measuring electrodes, leading to increased noise levels and the need for expensive materials, as conventional methods fail to effectively protect electrodes from corrosion across various media types.
Innovation Solution
The implementation of a constant direct current is applied to the measuring electrodes to lower their potential below a threshold value, utilizing a Pourbaix diagram to achieve corrosion immunity, allowing for the use of less expensive materials and reducing the need for material selection based on media type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expensive corrosion-resistant materials such as platinum are used for measuring electrodes, then corrosion resistance is improved, but device cost increases
Solution Approach 1:
The invention changes the electrochemical parameter (electrode potential) of the measuring electrode by applying a cathodic protection current. This shifts the electrode potential to a region where corrosion is suppressed, allowing the use of less expensive materials while maintaining corrosion resistance.
Solution Approach 2:
The invention introduces an external current source as an intermediary system that provides cathodic protection to the measuring electrode. This external current acts as a mediator to prevent corrosion without requiring the electrode material itself to be inherently corrosion-resistant.
2Reliability
If corrosion-resistant materials are used for measuring electrodes, then corrosion resistance is improved, but device complexity increases due to material selection requirements
Solution Approach 1:
The cathodic protection system provides a universal solution that works with various electrode materials and different media types. The same principle of applying negative current can protect any metallic electrode regardless of the specific material or medium, simplifying the overall system design.
3Ease of manufacture
If conventional electrode materials are used without corrosion protection, then device cost is reduced, but measurement precision deteriorates due to increased noise from corrosion
Solution Approach 1:
By changing the electrochemical potential parameter through cathodic protection, the invention eliminates corrosion-related noise while using inexpensive electrode materials, thereby maintaining measurement precision without increasing device cost.
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 approach effectively protects measuring electrodes from corrosion, enabling the use of cheaper materials and maintaining accurate flow measurements across different media conditions without adjusting electrode potentials, thus reducing sensor costs and inventory complexity.
Implementation Method 1
a current source for passing a constant direct current to each of the first and second metallic measuring electrodes, where the constant direct current passed to each of the first and second metallic measuring electrode is established to lower an electrode potential of a respective measuring electrode with respect to the medium to a level below a threshold value to render the respective metallic measuring electrode immune to corrosion with respect to the medium
Implementation Method 2
electromagnetic flowmeters, such as magnetic inductive flowmeters, utilize the principle of electrodynamic induction for flow rate measurement of a fluid medium. In an electromagnetic flowmeter, a magnetic field is generated across a measuring section of a flowmeter pipe through which the medium flows which, by operation of Faraday's law, generates a voltage perpendicular to the flow of the medium and the magnetic field
Data Source
AI summary
A system and method for corrosion protection of measuring electrodes in electromagnetic flowmeters, wherein a respective constant direct current is generated by a current source for first and second metallic measuring electrodes provided on opposite sides of a measuring tube, and the constant direct current is passed from the current source to the first and second metallic measuring electrodes, where the constant direct current passed to each metallic measuring electrode is established to lower the electrode potential of a respective measuring electrode with respect to the medium below a threshold value to render the respective metallic measuring electrode immune to corrosion with respect to a medium.