Flexible PCB Hall Current Sensor for Background Field Compensation
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Solution Overview
Problem
Existing current sensors for measuring large electric currents in conductors are either physically large and difficult to install, or require bulky magnetic shields to mitigate background magnetic field sensitivity.
Innovation Solution
A current sensor design featuring a flexible carrier with separate hall effect sensors mounted on opposing faces of the conductor, combined with a differential amplifier to compensate for background magnetic fields, allowing for accurate current measurement without the need for magnetic flux concentrators or apertures in the conductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a ferrite ring flux concentrator is used to measure current, then measurement precision is improved, but device complexity and installation difficulty increase
Solution Approach 1:
The sensor divides the measurement function into two separate hall effect sensors positioned at opposing faces of the conductor, each measuring local magnetic fields. This segmentation eliminates the need for a complex ferrite ring flux concentrator while maintaining measurement capability through differential processing of the two sensor outputs.
Solution Approach 2:
The patent combines the functions of magnetic field sensing and background field rejection into a single integrated sensor assembly with two hall effect sensors and differential amplifier. This merging achieves both measurement precision and simplicity by processing signals differentially to cancel common background fields.
2Measurement precision
If a ferrite ring flux concentrator is used, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
By segmenting the measurement into two independent hall effect sensors that can be independently positioned on opposing conductor faces, the installation process is simplified. Each sensor can be separately mounted without requiring complex assembly into a ferrite ring structure, making the sensor easier to install on existing conductors.
3Reliability
If a bulky magnetic shield is used to reduce background field sensitivity, then reliability is improved, but device complexity and size increase
Solution Approach 1:
Instead of using a magnetic shield to block background fields from reaching the sensor, the patent inverts the approach by using two sensors to detect background fields and mathematically subtracting them through differential amplification. This active cancellation method achieves background field rejection without requiring bulky passive magnetic shielding.
Solution Approach 2:
The differential amplifier acts as an intermediary that processes the signals from both hall effect sensors, combining the useful current measurement signals while canceling the common background magnetic field signals. This intermediary processing achieves background field rejection without physical shields.
4Measurement precision
If separate hall effect sensors are used on opposing faces, then background field compensation is achieved, but device complexity increases
Solution Approach 1:
The patent merges the functions of two separate hall effect sensors with a differential amplifier into an integrated sensor assembly. This combination achieves background field compensation through differential signal processing while maintaining a relatively simple overall structure that can be manufactured as a single unit or closely integrated 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
The solution enables precise measurement of electric current in conductors with large cross-sectional areas, improving installation ease and reducing sensitivity to background magnetic fields, thus enhancing the accuracy and reliability of current measurement.
Implementation Method 1
separate first and second hall effect sensors or hall sensor packages or components mounted on the carrier at the opposing faces or points of or around the conductor, each hall sensor being arranged to output a signal representative of a magnetic field at the respective sensor
Implementation Method 2
an amplifier or comparator, or more particularly a differential amplifier, which is also preferably mounted on the carrier, the amplifier or comparator being arranged to receive the signals from the first and second hall sensor packages and to combine the signals to provide at least one amplifier output representing the electric current within the conductor compensated to remove any background magnetic field common to the two hall effect sensors
Data Source
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AI summary
There is described an electrically powered vehicle comprising: an electrical conductor arranged to carry motive electric current for powering movement of the vehicle; and a current sensor arranged to measure the motive electric current in the electrical conductor, the current sensor comprising: a carrier extending around the conductor so as to be in confrontation with opposing faces of the electrical conductor; first and second hall sensor packages mounted on the carrier at the opposing faces of the conductor, each hall sensor package being arranged to output a signal representative of a magnetic field at the package; a differential amplifier mounted on the carrier to receive the signals from the first and second hall sensor packages and to combine the signals to provide at least one amplifier output representing the motive electrical current. The carrier may comprise a flexible PCB. There is also described a method of measuring electric current.