Cable Locator Self-Test via Direct Sensor Coupling
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Solution Overview
Problem
Existing cable locating instruments face challenges in achieving high accuracy and sensitivity due to imbalances in sensor transfer functions, susceptibility to environmental factors, and limitations in self-test measurements, leading to errors in depth calculation and signal rejection.
Innovation Solution
A detection apparatus with a self-test system that directly couples a programmable self-test signal into each sensor through a wired connection, using a digital-to-analog converter and current source to generate signals across a range of frequencies, allowing for precise phase balance determination and characterization of antenna responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a micro-sonde is used to energize sensors for self-test, then magnitude response can be compared, but measurement precision deteriorates due to susceptibility to position changes and magnetic field distortion
Solution Approach 1:
The invention extracts the self-test function from external micro-sonde equipment and integrates it directly into the sensor assembly through self-test windings. This eliminates the need for separate calibration equipment and removes the associated problems of position sensitivity and magnetic field distortion from external sources.
Solution Approach 2:
The self-test windings act as an intermediary mechanism that provides controlled magnetic field excitation directly to the ferrite core sensors. This intermediary structure enables precise self-testing without the uncertainties introduced by external micro-sonde positioning and operation.
2Reliability
If additional self-test windings are added to sensors, then separate energization of both antennas is possible, but device complexity increases and parasitic capacitance modifies transfer function
Solution Approach 1:
The self-test windings are designed to serve multiple functions: they provide separate energization of both antennas for self-testing, maintain the existing sensor functionality, and enable programmable frequency operation. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The system uses a programmable current source that can operate at multiple frequencies to energize the self-test windings. By changing operational parameters (frequency, current magnitude) rather than adding physical components, the system achieves versatile self-testing capability with minimal added complexity.
3Measurement precision
If more sensors are used to improve location accuracy, then location accuracy improves, but ease of operation deteriorates due to increased equipment unwieldiness
Solution Approach 1:
The invention combines multiple sensor elements into an integrated array with shared electronics and common self-test windings. This merging approach maintains the location accuracy benefits of multiple sensors while reducing overall equipment size and improving ease of operation through consolidation.
Solution Approach 2:
The sensor array is segmented into modular units, each with its own self-test capability through integrated windings. This segmentation allows for independent testing and calibration of individual sensor elements, simplifying operation and maintenance while maintaining high location accuracy through the combined array.
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 high-precision channel balancing, improved accuracy, and increased immunity to environmental factors, reducing errors and the need for frequent calibration, while enhancing the integrity and fidelity of detection measurements.
Implementation Method 1
the self-test signal is inductively coupled into the antenna
Implementation Method 2
a coil of wire wound on a ferrite core
Data Source
Figure 1
Figure 2~3
AI summary
A detection apparatus with a self-test is presented. A detection apparatus such as a cable locator has an array of sensors (1.1-1.3) in the form of ferrite antennas to detect an electromagnetic field produced by an object such as a buried cable. The signals are amplified, digitized and fed to a processing unit (4) that outputs a detection signal to a display to indicate the detection of a cable. A programmable signal generator outputs a self-test signal via a voltage-current converter that is used to check the balance between the sensors. The self-test signal is directly coupled into each of the sensors through a wired connection and the processing unit uses the self-test signal to accurately determine the magnitude and phase balance of the sensors. The magnitude and phase data may be used to calibrate the instrument, apply data corrections or flag errors.