Sensor Optimizing Signal Span to Offset Ratio
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Solution Overview
Problem
Existing sensors for measuring the relative position of a control rod within a nuclear reactor suffer from low signal span to offset ratio, leading to reduced accuracy and sensitivity, and require calibration due to unpredictable flux density and large residual magnetic fields.
Innovation Solution
A method using a sensor with primary and secondary electromagnetic coils made from a copper-manganese-nickel alloy, where the coils are wound around a core body matching the conductivity and permeability of the object, and the AC frequency is optimized to maximize the signal span to offset ratio, thereby improving accuracy and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple inductor principle is used in the sensor, then the device complexity is reduced, but the signal span to offset ratio decreases
Solution Approach 1:
The sensor is divided into multiple discrete coils (first coil, second coil, third coil, fourth coil) arranged in a specific pattern around the probe tube. This segmentation allows each coil to contribute to different aspects of the magnetic field generation and detection, enabling the system to achieve both structural simplicity and high measurement precision through coordinated operation of multiple simple elements
Solution Approach 2:
The patent combines the functions of multiple coils working together to generate and detect the magnetic field. The first and second coils generate the magnetic field while the third and fourth coils detect changes, merging the functions of field generation and detection into a unified sensor structure that achieves high signal span to offset ratio without excessive complexity
2Reliability
If transformer windings are used to generate magnetic field between primary and secondary windings, then the sensor can detect position through magnetic field changes, but a large residual magnetic field exists resulting in large voltage offset
Solution Approach 1:
The patent uses an asymmetric arrangement where the detection coils are positioned to detect only the changes in magnetic field caused by the leadscrew movement, while the residual magnetic field from the probe tube and windings is rejected. The specific geometric arrangement of coils at different positions around the tube creates an asymmetric detection pattern that cancels out the offset
Solution Approach 2:
The patent extracts and eliminates the offset component from the measurement signal. By using multiple coils in a specific configuration and processing their combined output, the system separates the useful signal (caused by leadscrew position changes) from the unwanted offset (caused by residual magnetic field), effectively removing the offset to improve measurement precision
3Measurement precision
If multiple inductive elements are manufactured and calibrated in situ to achieve best magnetic field, then the measurement accuracy can be optimized, but the manufacturing complexity and time increase
Solution Approach 1:
The patent achieves high measurement accuracy through careful selection and optimization of geometric parameters of the coils (such as their positions, dimensions, and spacing) and material properties, rather than through extensive manufacturing variations and in-situ calibration. The design uses fixed geometric ratios and standardized dimensions that can be manufactured with常规 precision while still achieving optimal magnetic field characteristics
Solution Approach 2:
The patent performs preliminary optimization of the sensor design through theoretical calculation and simulation before manufacture. The coil configurations and geometric parameters are predetermined based on analytical models of the magnetic field, allowing the sensor to achieve high accuracy directly from the manufacturing process without requiring time-consuming in-situ calibration of multiple prototypes
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 significantly enhances the signal span to offset ratio, providing higher resolution and accuracy in determining the relative position of the control rod, reducing errors and improving measurement precision.
Implementation Method 1
supplying the primary coil(s) with an alternating current to result in the generated time varying magnetic field
Implementation Method 2
a secondary electromagnetic coil arranged to detect the time varying magnetic field and to output, on the basis of the detected time varying magnetic field, a signal
Implementation Method 3
the voltage across the inductor changes because of magnetic coupling effects
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A method of optimising the output of a sensor for indicating the relative location of a metallic object. The sensor is of the type having a primary electromagnetic coil arranged to generate a time varying magnetic field; and a secondary electromagnetic coil arranged to detect the time varying magnetic field as affected, directly or indirectly, by the object and to output, on the basis of the detected time varying magnetic field, a signal indicative of the relative location of the object. The method includes the steps of: supplying the primary coil with an alternating current to result in the generated time varying magnetic field; locating the object in a first position and recording the signal output by the secondary electromagnetic coil for a range of respective frequencies of the supplied alternating current; locating the object in a second position and recording the signal output by the secondary electromagnetic coil for the range of respective frequencies of the supplied alternating current; calculating, for each of the respective frequencies, a value for the span to offset ratio of the measured signals on the basis of the respective signals measured for the object in the first and second positions; and determining the frequency of the supplied alternating current which provides the maximum span to offset ratio on the basis of the calculations.