Scanning Detector Phase Slope Discrimination
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Solution Overview
Problem
Existing handheld scanning detectors cannot distinguish between iron-based and non-magnetic, highly conductive metallic objects, such as copper, especially when they are in close proximity, leading to difficulties in accurately identifying subsurface structures in concrete or masonry.
Innovation Solution
A handheld scanning detector equipped with a field-sensor comprising a pair of primary pickup-coils and an excitation-coil arrangement, which generates an alternating magnetic field and measures the phase difference between the excitation current and induced voltage signals, allowing the interpretation unit to differentiate between iron-based and copper-based objects by analyzing the slope of the phase and magnitude of eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional scanning detector is used to detect subsurface structures, then the detector can identify the presence of metallic objects, but it cannot distinguish between different materials (iron-based vs. copper-based) when they are in close proximity
Solution Approach 1:
The patent applies parameter changes by measuring the phase angle of the voltage signal at two different excitation frequencies (first and second frequencies). By comparing the phase angles at these different frequencies, the system can distinguish between iron-based and copper-based objects. The phase angle response to frequency changes differs characteristically between these material types, enabling material differentiation without requiring the detector to physically separate or reconfigure for different detection modes.
2Measurement precision
If the detector uses a single frequency excitation, then the device complexity is low, but the measurement precision for material identification is insufficient
Solution Approach 1:
The patent employs periodic action by using alternating excitation at two distinct frequencies. The excitation signal is periodically switched between the first frequency and the second frequency, and the phase angle measurements are taken correspondingly. This periodic multi-frequency excitation enables material identification through frequency-dependent phase response while maintaining a relatively simple system architecture that can be implemented with standard signal generation and measurement circuits.
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
Effectively identifies and discriminates between iron-based and copper-based objects, even when they are in close proximity, improving the accuracy of subsurface structure detection and material composition analysis.
Implementation Method 1
A current source (31) injects an alternating excitation-current (33) in the excitation-coil arrangement (22, 23). Thus, the excitation-coils are emitting a corresponding alternating magnetic field.
Implementation Method 2
A phase-analyser (38) determines a phase (phi) between the alternating excitation-current (33) and a difference of induced voltage-signals (36) in the primary pickup-coils (24, 25).
Implementation Method 3
A magnitude-analyser (42) determines a magnitude of eddy currents (41) in the primary pickup-coils (24, 25), or the secondary pickup-coils (26, 27).
Data Source
Figure 1~3
Figure 4~6
AI summary
The scanning detector (1) is designed to detect and to identify first structures (2) only made of iron-based objects (7) and second structures (6) comprising iron-based objects (7) and non-magnetic and highly conductive metallic objects (8). The structures are below a surface, for instance embedded in masonry. A movement sensor (13) determines a movement of the scanning detector (1) along a measuring-direction (9). A field-sensor (13) comprises a pair of primary pickup-coils (24, 25) along the measuring-direction (9) and an excitation-coil arrangement (22, 23) arranged between the primary pickup-coils (24, 25). A current source (31) injects an alternating excitation-current (33) in the excitation-coil arrangement (22, 23). Thus, the excitation-coils are emitting a corresponding alternating magnetic field. A phase-analyser (38) determines a phase (phi) between the alternating excitation-current (33) and a difference (36) of induced voltage-signal (34 in the primary pickup-coils (24, 25). An interpretation unit (17) determines a slope of the phase (phi). The interpretation unit (17) identifies a structure by discriminating among the first structures (2) and the second structures (6) based on whether the slope is increasing or decreasing. A display (18) or a transceiver (20) is used to inform the user about the identified structure.