Magnetoresistive Sensor with Auxiliary Coil for Current Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring small current signals on top of or after high current peaks face challenges such as accuracy issues due to resistance heating, integration offsets, and hysteresis effects in magnetic field sensors, making it difficult to detect small variations accurately.
Innovation Solution
A sensor unit comprising at least one magnetoresistive sensor located at a radial distance from the conductor with a circular cross-section, utilizing an auxiliary coil to generate a continuous bias magnetic field that induces magnetic saturation, allowing direct measurement of the magnetic field generated by the current, and using the angular dependency of the measurement signal for high sensitivity and reduced offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor is used to measure current directly, then the current can be measured directly from voltage drop, but the resistance heats up during peak current and changes characteristics, reducing measurement accuracy for small currents after the peak
Solution Approach 1:
The patent replaces the electrical measurement method (voltage drop across shunt resistor) with a magnetic field-based measurement method. A magnetoresistive sensor detects the magnetic field generated by the current, eliminating the need for additional resistance in the circuit and thus avoiding heating problems while maintaining measurement capability.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the current to be measured and the sensor. Instead of directly measuring electrical properties that cause heating, the system measures the magnetic field generated by the current, which serves as a mediator that doesn't suffer from thermal effects.
2Measurement precision
If a coil is used to detect magnetic field changes, then the current can be measured through induced voltage, but integration adds up errors resulting in offset that prevents accurate measurement of small currents after large peaks
Solution Approach 1:
The patent replaces the coil-based inductive measurement method with a magnetoresistive sensor that directly measures magnetic field strength. This substitution eliminates the need for signal integration, thereby removing the source of integration offsets and enabling accurate measurement of small currents even after large current peaks.
Solution Approach 2:
The patent uses a magnetoresistive sensor that creates a direct copy of the magnetic field distribution without requiring mathematical integration. The sensor's resistance changes directly reflect the local magnetic field strength, providing an immediate measurement without accumulating errors over time.
3Measurement precision
If ferromagnetic core is added to enhance magnetic field signal, then sensitivity is improved, but high magnetic fields magnetize the material causing distortion and additional offsets due to hysteresis effects
Solution Approach 1:
The patent replaces ferromagnetic materials with magnetoresistive materials that have different characteristics. The magnetoresistive sensor detects magnetic field changes through resistance changes without the hysteresis effects that plague ferromagnetic materials, enabling accurate measurement even in the presence of strong magnetic fields from large current peaks.
Solution Approach 2:
The patent changes the material parameter from ferromagnetic to magnetoresistive. This parameter change fundamentally alters how the material responds to magnetic fields, eliminating hysteresis and saturation effects while maintaining high sensitivity to magnetic field changes.
4Measurement precision
If magnetic field sensors with high sensitivity are used, then small current signals can be detected, but offsets are still present due to hysteresis effects in the magnetic materials
Solution Approach 1:
The patent changes the material parameter from conventional magnetic materials to magnetoresistive materials. This parameter change maintains high sensitivity for detecting small current signals while eliminating the hysteresis offsets that are inherent in traditional magnetic field sensors.
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 detection of small current variations up to 1MHz without signal distortion or offset, maintaining high resolution and sensitivity even during large current peaks, and effectively compensates for external field contributions.
Implementation Method 1
The auxiliary coil is located such as to apply this bias magnetic field to the magnetoresistive sensor
Implementation Method 2
it is strong enough at the position of the sensor for inducing magnetic saturation in the magnetoresistive sensor
Implementation Method 3
at least one magnetoresistive sensor located at a radial distance from the outer surface of the conductor
Data Source
Figure 1~4
Figure 5~6
Figure 7~8
AI summary
A sensor unit for the measurement of a current in a conductor (1) comprising at least one magnetoresistive sensor (5, 6) located at a radial distance from the outer surface of the conductor (1) is disclosed, wherein the conductor (1) has a circular cross-section, and wherein it comprises at least one auxiliary coil (7) for the generation of a bias magnetic field (Hbias) to the magnetoresistive sensor (5, 6) strong enough for inducing magnetic saturation in the magnetoresistive sensor (5, 6) continuously during the whole current measurement process. Further the use of such a sensor and a method for measuring the current in the conductor using such a sensor unit are disclosed.