Rogowski Coil Clamp-On Multimeter for High Current Measurement
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Solution Overview
Problem
Conventional multimeters require breaking the current-carrying conductor to measure current, limiting their maximum current measurement capacity and being cumbersome in tight spaces due to heavy magnetic cores and alignment requirements.
Innovation Solution
A multimeter kit incorporating a Rogowski coil and a clamp with magnetizable cores, allowing non-contact inductive sensing of alternating current without breaking the circuit, featuring a flexible Rogowski coil for use in confined spaces and high current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a clamp-on multimeter with a magnetic core is used to measure current, then current measurement capability is improved, but the device becomes physically heavy and difficult to use in tight spaces
Solution Approach 1:
The patent extracts the heavy magnetic core from the measurement system by replacing it with a Rogowski coil that uses air as its core. This extraction eliminates the weight problem while maintaining current measurement capability through inductive sensing, directly resolving the contradiction between measurement capability and device weight.
Solution Approach 2:
The patent replaces the mechanical magnetic core system with an electromagnetic Rogowski coil system. The coil uses electromagnetic induction rather than magnetic saturation to measure current, substituting a lightweight electromagnetic structure for a heavy mechanical magnetic structure, thereby reducing weight while preserving measurement function.
2Measurement precision
If a clamp-on multimeter with a magnetic core is used to measure current, then current measurement capability is improved, but the device requires large physical space for jaw alignment
Solution Approach 1:
The patent removes the rigid magnetic core structure that requires jaw alignment and mechanical closing. The Rogowski coil can be opened completely and wrapped around conductors of various shapes and sizes without requiring precise alignment, eliminating the space requirement issue while maintaining measurement capability.
Solution Approach 2:
The patent transforms the static, rigid jaw structure into a dynamic, flexible Rogowski coil that can be opened, wrapped around the conductor, and closed. This dynamic approach allows the measurement device to adapt to different conductor configurations in tight spaces without requiring large alignment areas.
3Measurement precision
If a magnetic core is used in the current clamp, then current sensing is enabled, but the magnetic core becomes saturated at high current levels
Solution Approach 1:
The patent extracts the magnetic core from the system and replaces it with an air-core Rogowski coil. This elimination of the magnetic core removes the saturation limitation entirely, as air does not saturate, thereby extending the measurable current range to very high levels while maintaining sensing capability through electromagnetic induction.
Solution Approach 2:
The patent changes the core material parameter from ferromagnetic material with saturation characteristics to air with no saturation characteristics. This parameter change fundamentally alters the current measurement range, allowing the device to handle high current levels without saturation while maintaining accurate sensing through the Rogowski coil's inductive response.
4Measurement precision
If an internal current shunt is used in a multimeter, then current measurement is enabled, but the maximum current capacity is limited to ten amperes
Solution Approach 1:
The patent replaces the internal current shunt system with an external Rogowski coil system that measures current through electromagnetic induction. This substitution eliminates the current capacity limitation of the shunt and fuse, allowing measurement of very high current levels without breaking the circuit or requiring current-limiting components.
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
Enables accurate and flexible measurement of alternating current in tight spaces with higher current capacity and no risk of magnetic core saturation, eliminating the need for internal fuses and reducing physical constraints.
Implementation Method 1
A Rogowski coil adapted for use with a multimeter for inductive sensing of alternating current without breaking an electrical circuit that includes the conductor
Implementation Method 2
The current clamp is closed around the current-carrying conductor, which may include copper wires and buss bars, to sense the magnetic field created by the current flow
Data Source
AI summary
A clamp-on multimeter measures alternating current flow in an electrical conductor. The multimeter includes a display, a housing including the display, a first sensor, a second sensor, a processor and an integrator. The first sensor has a magnetizable material core and inductively senses the alternating current. The first sensor includes a first clamp portion fixed to the housing and a second clamp portion pivotally coupled to the first clamp portion. The second sensor includes a Rogowski coil that has a non-magnetic core and inductively senses the alternating current. The processor receives an input signal in a first voltage range and sends an output signal to the digital display. The integrator scales a signal from the second sensor in a second voltage range to the first voltage range. The housing includes the processor, the integrator, and a selector configured to select the input signal to the processor from one of the first sensor and the integrator.