Low-Resistance Current-Measuring Resistor with Localized Coating
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Solution Overview
Problem
Existing low-resistance current-measuring resistors face issues with oxidation, leading to unsightly discoloration and impaired solderability, and previous solutions like galvanic coatings can be electrically conductive, causing resistance falsification or requiring laborious manual application of insulating coatings.
Innovation Solution
Applying a metallic coating directly to the entire free surface of the resistor element without an insulation layer, using materials like nickel-phosphorus with low electrical conductivity and high specific resistance, and ensuring the coating is thin and envelops the resistor circumferentially to prevent electrical bypass and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a metallic coating is applied to prevent oxidation, then surface protection is improved, but electrical conductivity increases causing resistance falsification
Solution Approach 1:
The patent applies different materials to different surfaces of the same component. The lateral edges receive an electrically insulating coating to prevent bypass currents, while the top and bottom surfaces receive a conductive metallic coating for oxidation protection and solderability. This local differentiation resolves the contradiction by providing oxidation protection where conductivity is needed while preventing resistance falsification where insulation is required.
Solution Approach 2:
The coating is divided into functionally distinct segments: an insulating coating segment on the lateral edges and a metallic coating segment on the top and bottom surfaces. This segmentation allows each portion to fulfill its specific function without interfering with the other, thereby preventing both oxidation and resistance falsification simultaneously.
2Measurement precision
If an electrically insulating coating is applied to prevent resistance falsification, then measurement precision is improved, but manufacturing complexity increases due to laborious manual application
Solution Approach 1:
The resistor element is prepared with pre-defined surface characteristics before coating application. The lateral edges are specifically prepared to receive insulating coating while top and bottom surfaces are prepared for metallic coating. This preliminary preparation enables automated or semi-automated coating processes rather than requiring laborious manual application, thus improving manufacturing efficiency while maintaining measurement precision.
3Object-affected harmful factors
If the entire resistor is galvanized for complete oxidation protection, then surface protection is improved, but electrical conductivity increases causing substantial resistance falsification
Solution Approach 1:
Instead of uniform galvanization, the patent applies insulating coating specifically to the lateral edges where bypass currents would occur, while allowing metallic coating on top and bottom surfaces for oxidation protection. This local quality approach prevents resistance falsification while maintaining necessary oxidation protection.
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 simplifies manufacturing by eliminating the need for manual paint application, minimizes electrical bypass, maintains resistance accuracy, and ensures effective surface protection while maintaining temperature constancy and solderability.
Implementation Method 1
the material of the connection parts and the resistor element oxidizes so that such current-measuring resistors then turn brown and look unattractive, the solderability also being impaired through the oxidation
Implementation Method 2
said material having sufficiently low electrical conductivity and sufficiently high specific electrical resistance. Nickel-phosphorus (NiP) is preferably used as the material for the metallic coating
Implementation Method 3
A known method to solve this problem is to galvanically tin-plate or nickel-plate the composite material strip
Data Source
AI summary
The invention relates to a resistor, in particular a low-resistance current-measuring resistor, comprising a first connection part (1) that consists of a conductor material for introducing an electrical current (I), a second connection part (2) that consists of a conductor material for discharging said electrical current (I), and a resistor element (3) that consists of a resistor material and is arranged between the two connection parts (1, 2) in the direction of the current, also comprising a resistor coating (7) that consists of a metallic material for the purpose of achieving protection from corrosion, and/or improving solderability. According to the invention, the metallic coating (7) is applied directly to the entire free surface of the resistor element (3) without any insulation layer.