PPG Sensor Current-Gain Calibration for Stable Signal Levels
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Solution Overview
Problem
Existing PPG signal acquisition methods face challenges in achieving an appropriate signal level for different users, leading to signal saturation or low signal-to-noise ratio, which affects the accuracy of bio information extraction.
Innovation Solution
An electronic device controls the current and gain values of a PPG sensor using a specified range and stored PPG models to adapt to individual users, allowing for one-time measurement to achieve a specified PPG signal level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If automatic gain control is repeatedly performed to adapt current and gain values for different users, then the PPG signal level becomes appropriate for bio information extraction, but PPG signal delay and distortion occur leading to measurement errors
Solution Approach 1:
The system performs preliminary characterization of skin optical properties before actual PPG measurement. By pre-determining the relationship between LED current and detected signal intensity for each user's skin type, the system establishes optimal measurement parameters in advance, eliminating the need for repeated AGC adjustments during actual measurement and thus preventing signal distortion and discontinuity.
Solution Approach 2:
The system uses the PPG sensor itself to characterize the user's skin optical properties during an initial calibration phase. By measuring the user's specific skin characteristics with the same sensor that will be used for actual bio information measurement, the system creates user-specific calibration data that enables accurate measurement without requiring external calibration equipment or repeated adjustments.
2Measurement precision
If multiple PPG measurements are performed with different current and gain values to find appropriate signal level, then accurate bio information can be acquired, but measurement time increases and productivity decreases
Solution Approach 1:
The system performs preliminary characterization of skin optical properties before actual PPG measurement. By pre-determining the relationship between LED current and detected signal intensity for each user's skin type, the system establishes optimal measurement parameters in advance, eliminating the need for repeated AGC adjustments during actual measurement and thus preventing signal distortion and discontinuity.
3Measurement precision
If high current intensity is applied to the light emitter to increase PPG signal level, then signal to noise ratio improves, but signal saturation occurs making bio information extraction difficult
Solution Approach 1:
The system dynamically adjusts the LED current parameter based on the detected skin optical properties. By changing the current parameter according to each user's specific skin characteristics (stored in the database), the system optimizes the balance between signal intensity and saturation, ensuring the PPG signal remains within the optimal measurement range for accurate bio information extraction.
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 enables accurate bio information acquisition by adjusting current and gain values based on user-specific models, minimizing measurement delays and distortions, and ensuring a stable signal level.
Implementation Method 1
The PPG sensor may include a light emitter (e.g., LED) that emits light
Implementation Method 2
the light detector may collect the reflected light. The light collected by the light detector may be transformed into an electrical signal
Data Source
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AI summary
An electronic device is disclosed. According to an embodiment disclosed herein, an electronic device may include a PPG sensor including a light emitter that applies a current in a specified range and emits a light signal corresponding to the current and a light detector that amplifies a received light signal by applying one of a plurality of gain values, a memory that stores a plurality of sets of PPG models corresponding to the plurality of gain values and including a current value and PPG level data corresponding to the current value, and at least one processor electrically connected to the PPG sensor and the memory, wherein the at least one processor may acquire a first PPG signal from the PPG sensor set with a first current value satisfying the specified range and a first gain value of the plurality of gain values when a user's contact is detected by the PPG sensor, generate a first PPG model corresponding to the user based on a first PPG model set corresponding to the first gain value among the plurality of sets of PPG models, the first current value and the first PPG signal, determine a second gain value and a second current value for acquiring a PPG signal with a specified PPG level, based at least on the first PPG model set, and acquire a second PPG signal with the specified PPG level using the PPG sensor set with the second gain value and the second current value. In addition, various embodiments understood from the specification are possible.