Interferometric Sensor Phase Shift Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Interferometric sensors face a periodwise ambiguity issue, limiting their unambiguous measurement range for DC voltage or current measurements due to the absence of an oscillating waveform, making it difficult to distinguish phase shifts and resulting in measurement range constraints.
Innovation Solution
The implementation of a phase shift detection unit and a contrast detection unit within an interferometric sensor, which measures the principal value of the relative phase shift and the cross-correlation between waves, respectively, allowing for the conversion of these measures into an unambiguous measurand value by using a pre-determined function or map, thereby removing periodwise ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interferometric measurement is used to measure DC voltage or current, then phase shift can be detected, but periodwise ambiguity limits the unambiguous measurement range to π-voltage
Solution Approach 1:
The patent introduces a new dimension of measurement by detecting not only the phase shift φ but also the interference contrast A(φ). This additional dimension allows the system to distinguish between different periods of phase shift, thereby eliminating the periodwise ambiguity that limits measurement range to π-voltage. The combined measurement of phase and contrast enables unambiguous measurement beyond the traditional limit.
Solution Approach 2:
The interference contrast A(φ) acts as an intermediary parameter that provides additional information about the phase shift period. By measuring both the phase shift φ and the contrast A(φ), the system can determine the correct period assignment and resolve the ambiguity between φ and φ+2nπ, enabling extended measurement range without losing information.
2Measurement precision
If quadrature signals are combined to remove sign ambiguity, then φ and −φ can be distinguished, but periodwise ambiguity between φ and φ+2nπ remains
Solution Approach 1:
The patent extends the measurement by adding the interference contrast dimension. While quadrature signals resolve the sign ambiguity (φ vs -φ), the contrast measurement A(φ) provides additional information that resolves the periodwise ambiguity (φ vs φ+2nπ). This dimensional extension enables complete unambiguous measurement of the phase shift over an extended range.
3Measurement precision
If fringe counting or zero-counting techniques are used to extend measurement range, then AC voltage measurements can reach many times π-voltage, but these techniques require history information that is unavailable or unreliable for DC measurements
Solution Approach 1:
The interference contrast A(φ) serves as a reliable intermediary that provides immediate information about the phase shift period without requiring historical data. Unlike fringe counting or zero-counting methods that depend on tracking changes over time, the contrast measurement gives direct information about the current state, making it reliable for DC measurements where history information is unavailable or unreliable.
Solution Approach 2:
The patent replaces the time-based history-tracking approach (fringe counting, zero-counting) with a simultaneous measurement approach using interference contrast. Instead of tracking phase changes over time to determine period assignment, the system measures both phase and contrast at the same instant, eliminating the need for historical information and improving reliability for DC measurements.
4Measurement precision
If two distinct optical wavelengths are used to extend measurement range, then periodwise ambiguity is eliminated, but device complexity increases significantly due to requiring at least two sets of light sources and detectors
Solution Approach 1:
The patent makes the single optical wavelength system multi-functional by extracting multiple measurement dimensions (phase shift φ and interference contrast A(φ)) from a single wavelength measurement. This eliminates the need for multiple light sources and detectors required by multi-wavelength approaches, thereby reducing device complexity while achieving extended measurement range and unambiguous measurements.
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 increases the unambiguous measurement range of interferometric sensors by accurately determining the relative phase shift, enabling precise measurement of DC voltages or currents beyond the traditional π limit, especially suitable for medium or high voltage applications.
Implementation Method 1
a sensing element whereby a measurand induces a relative phase shift between two waves
Implementation Method 2
at least one detector measuring an interference signal between the two waves
Data Source
AI summary
An interferometric sensor and related methods are provided, with a sensing element whereby a measurand induces a relative phase shift between two waves, at least one detector measuring an interference signal between the two waves, and further including a phase shift detection unit having as input the interference signal and determining a first measure representative of the principal value of the relative phase shift, and a contrast detection unit having as input the interference signal for determining a second measure representative of the cross-correlation between the two waves, and a further a processing unit for converting the first and second measures to a measurand value.