Electrical Plug Contacts for Four-Wire Socket Resistance Testing

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Solution Overview

Problem

Existing electrical socket testing methods struggle to accurately measure resistance and identify defective socket contacts due to lead resistances and contact errors, which can lead to inaccurate readings and potential fire hazards.

Innovation Solution

An electrical plug with multiple isolated electrical contacts that allow for four-terminal sensing, enabling precise resistance and impedance measurements by isolating contact points and using Kelvin connections, thereby eliminating lead resistance errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional two-wire testing methods are used to measure socket resistance, then the testing process is simple, but lead resistances and contact errors cause inaccurate readings

Engineering Contradiction:
Improveresistance measurement accuracyVSAvoidtesting method complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The pin is divided into multiple electrically isolated contact portions (first contact portion, second contact portion, third contact portion, fourth contact portion) that can independently engage with different regions of the pin receptor. This segmentation allows separate current and voltage measurement paths, eliminating lead resistance errors through four-wire sensing while maintaining a simple plug structure.

Inventive Principle:
Principle #1Segmentation

2Reliability

If multiple electrical contacts are integrated into a single pin, then the plug structure remains simple, but accurate isolation and measurement become difficult

Engineering Contradiction:
Improvecontact isolation reliabilityVSAvoidpin structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

Multiple electrically isolated contact portions are merged into a single pin structure. The first and second contact portions engage with a first pin receptor region, while the third and fourth contact portions engage with a second pin receptor region. This merging maintains structural simplicity while achieving reliable electrical isolation through separate contact zones.

Inventive Principle:
Principle #5Merging (Combining)

3Measurement precision

If four-wire sensing is implemented to eliminate lead resistance errors, then measurement precision improves, but the testing system becomes more complex

Engineering Contradiction:
Improveimpedance measurement accuracyVSAvoidsensing circuit complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The plug itself provides the four-wire sensing capability through its multi-contact design. The first and second contact portions serve as current carrying contacts, while the third and fourth contact portions serve as voltage sensing contacts. This self-service approach eliminates the need for external four-wire sensing equipment, maintaining simplicity while achieving high precision measurements.

Inventive Principle:
Principle #25Self-service

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

The plug provides accurate resistance and impedance measurements, identifying defective socket contacts and reducing fire risks by ensuring precise electrical testing without nulling lead resistances.

Implementation Method 1

a first pin for engagement with a first pin receptor of the electrical mains socket, wherein the first pin comprises first and second electrical contacts, each comprising a surface portion to engage with a different respective region of the first pin receptor

Methodology Applied
Scientific EffectElectrical Conduction: Conduction (electrical)

Implementation Method 2

a circuit connected to the first, second, third, and fourth electrical contacts, and configured to measure, by four-wire sensing, at least one of an impedance and a resistance of an electrical installation connected to the electrical mains socket

Methodology Applied
Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentEP3807659B1Electrical plug and methods for testing an electrical mains socket and an electrical mains plug
Publication Date: 2025.08.06 MEGGER INSTRUMENTS LTD
  • EP3807659B1 patent drawingFigure 1~2
  • EP3807659B1 patent drawingFigure 3
  • EP3807659B1 patent drawingFigure 4

AI summary

An electrical plug (1) for testing an electrical mains socket (2) is provided. The electrical plug (1) comprises a pin (12) for engagement with a pin receptor (4) of the electrical mains socket (2). The pin (12) comprises first (13) and second (14) electrical contacts, each comprising a surface portion to engage with a different respective region of the pin receptor (4). The first (13) and second (14) electrical contacts are electrically isolated from one another at the pin (12). An electrical testing system and a method of testing an electrical mains socket (2) is provided. The electrical testing system comprises the electrical plug (1) and a first circuit (16) connected to the first (13) and second (14) electrical contacts and configured to measure an electrical resistance therebetween. The method includes providing the electrical plug (1) and measuring an electrical resistance between the first (13) and second (14) electrical contacts. A further method is provided for testing an electrical mains plug (61) comprising a pin (62), by providing an electrical socket (63) with a pin receptor (64) having first (65) and second (66) regions electrically isolated from one another.