Dual-Strap Wearable Sensor Switching for ECG and PPG Accuracy
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Solution Overview
Problem
Wrist-based activity trackers using both PPG and ECG sensors suffer from inaccurate heart rate readings due to motion artifact and interference, particularly when both sensors are activated simultaneously, leading to high false readings and reduced battery life.
Innovation Solution
A wearable device that can be attached to either a chest strap for ECG measurements or an arm/wrist strap for PPG measurements, with control circuitry to switch between ECG only and PPG only modes, deactivating the unnecessary sensor to reduce noise and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both PPG and ECG sensors are activated simultaneously in wrist-based devices, then more comprehensive heart rate data can be collected, but measurement accuracy deteriorates due to motion artifact and interference
Solution Approach 1:
The patent implements dynamic sensor activation where the control circuitry switches between PPG-only mode and ECG-only mode based on real-time motion detection. When motion artifact is detected, the system dynamically deactivates the ECG sensor to prevent interference, while maintaining PPG operation. This dynamic adaptation resolves the contradiction by making sensor activation conditional rather than simultaneous and static.
Solution Approach 2:
The system employs periodic motion detection and sensor switching, where the control circuitry continuously monitors for motion artifacts and periodically switches between sensor modes. This periodic action allows comprehensive data collection during low-motion periods while maintaining measurement accuracy during high-motion periods by activating only the appropriate sensor.
2Reliability
If both PPG and ECG sensors operate continuously, then more complete monitoring coverage is achieved, but energy consumption increases
Solution Approach 1:
The control circuitry dynamically manages sensor operation based on detected activity state. During periods of detected motion or activity, the system activates only the necessary sensor (PPG for wrist, ECG for chest), deactivating the other to conserve energy. During rest periods, both sensors can operate to provide comprehensive monitoring coverage, thus resolving the contradiction between reliability and energy consumption.
Solution Approach 2:
The system temporarily discards (deactivates) one sensor mode when the other is sufficient, recovering (reactivating) it when needed. For example, during exercise detected by motion sensors, the system discards ECG operation in favor of PPG to save energy, then recovers ECG functionality when the user returns to rest, maintaining monitoring coverage while managing power consumption.
3Adaptability or versatility
If the device is designed to work with both chest strap and arm strap, then versatility is improved, but device complexity increases
Solution Approach 1:
The wearable device is designed with universal functionality to operate with both chest straps and arm straps using the same sensor module. The control circuitry automatically detects the wear location and configures the appropriate sensor mode (ECG for chest, PPG for wrist), eliminating the need for separate dedicated devices and reducing overall system complexity through multi-functionality.
Solution Approach 2:
The device employs dynamic configuration where the control circuitry automatically adjusts which sensor operates based on detected strap type and wear location. This dynamic adaptation simplifies the user experience despite the ability to work with multiple strap types, as the switching logic is automated rather than requiring manual configuration or complex mechanical changes.
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
Improves measurement accuracy by reducing noise and interference, enhances battery life by conserving power, and eliminates accidental triggering of measurements.
Implementation Method 1
They can include an optical blood flow sensor, such as a photoplethysmogram (PPG) sensor. These sensors use flashing LEDs to penetrate the user's skin and detect blood flow, and therefore pulse and heart rate.
Implementation Method 2
Chest-based devices often include electrocardiogram (ECG) sensors, which monitor heart rate using detected electrical signals of the heart.
Data Source
AI summary
A wearable device for monitoring physical activity of a user, the wearable device being reversibly attachable to a chest strap and an arm strap. The wearable device comprises an ECG sensor arranged to collect ECG measurements of the user only when the wearable device is attached to the user's chest by the chest strap, and a PPG sensor arranged to collect PPG measurements of the user when the wearable device is attached to the user's arm or wrist by the arm strap. The wearable device also comprises control circuitry arranged to switch the wearable device between an ECG only mode and a PPG only mode. In the ECG only mode, the control circuitry is configured to control the ECG sensor to collect ECG measurements but prevent the PPG sensor from initiating PPG measurements. In the PPG only mode, the control circuitry is configured to control the PPG sensor to initiate PPG measurements but prevent the ECG sensor from collecting ECG measurements.