Capacitive Blood Pulse Sensor with Shielded E-Field
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Solution Overview
Problem
Current methods for noninvasive measurement of blood flow, such as palpation, are limited in accuracy and convenience, particularly for measuring vascular pulsation without direct contact or invasive procedures.
Innovation Solution
A capacitive sensing system utilizing a capacitive sensor with a sensor electrode and shield, positioned near skin pulse points, generates and concentrates an electric field to measure capacitance changes corresponding to vascular pulsation, converting these measurements into data representative of heart rate through a capacitance-to-digital conversion unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If palpation (touch) is used to examine arterial pulse, then the measurement can be performed with simple equipment, but the measurement precision and reliability are limited
Solution Approach 1:
The patent replaces the mechanical palpation method with a capacitive sensing system that uses electrical fields to detect skin displacement caused by arterial pulse. The capacitive sensor measures changes in capacitance as the skin moves toward and away from the sensor electrode during pulse waves, converting mechanical displacement into electrical signals for precise measurement without direct mechanical contact.
Solution Approach 2:
The patent introduces an electric field as an intermediary between the sensor and the arterial pulse. The capacitive sensor creates an electric field that interacts with the skin surface, and changes in the electric field caused by skin displacement are measured to detect pulse. This intermediary approach allows non-contact measurement while maintaining high precision.
2Ease of operation
If direct contact methods are used for pulse measurement, then the measurement can be obtained, but the convenience and user experience are reduced
Solution Approach 1:
The patent replaces direct mechanical contact with capacitive sensing that operates through near-field electrical interaction. The sensor electrode generates an electric field that penetrates through air or minimal contact to the skin surface, detecting pulse-induced skin displacement without requiring firm physical contact. This maintains measurement precision while significantly improving ease of operation and user comfort.
3Ease of operation
If capacitive sensing is used for noninvasive measurement, then the convenience and noninvasive nature are improved, but the measurement precision may be affected by environmental factors
Solution Approach 1:
The patent divides the capacitive sensing system into functionally independent components: a sensor electrode for generating the electric field, a sensor shield for blocking external electrical interference, and signal processing circuitry. The shield is specifically designed to segment and isolate the sensing region from environmental electromagnetic noise, maintaining measurement reliability in noninvasive applications.
Solution Approach 2:
The patent addresses the vulnerability of capacitive sensing to environmental electromagnetic interference by introducing a driven shield that generates a counteracting electric field. The shield is driven at the same frequency and phase as the sensor electrode, creating an opposing field that cancels out external interference and stabilizes the measurement, converting the potential harm of environmental noise into a controlled condition.
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
Enables accurate, noninvasive, and convenient measurement of vascular pulsation, allowing for continuous monitoring of heart rate without direct contact, enhancing measurement precision and user experience.
Implementation Method 1
exciting the sensor electrode to generate a sensor E-field between the sensor electrode and the skin pulse point based on sensor self-capacitance
Implementation Method 2
generate a sensor E-field between the sensor electrode and the skin pulse point
Implementation Method 3
driving sensor shield to generate a shield E-field such that the sensor E-field is concentrated in the direction of the skin pulse point
Implementation Method 4
acquiring capacitance measurements for a proximal self-capacitance of the sensor electrode with the skin pulse point at proximal displacement, and a distal self-capacitance of the sensor electrode with the skin pulse point at distal displacement
Data Source
AI summary
A capacitive sensing system is adapted for noninvasive measurement of blood pulse (hear rate). A capacitive sensor is located near a skin pulse point exhibiting pulse displacement of skin tissue from vascular pulsation (for example, the temple area of the head), and includes a sensor electrode disposed over and spaced from the skin pulse point, such that the distance between sensor electrode and the skin pulse point cycles between a proximal and a distal displacement distance based on vascular pulsation. A capacitance-to-digital conversion (CDC) unit includes excitation circuitry providing sensor excitation to generate a sensor E-field between the sensor electrode and the skin pulse point based on sensor self-capacitance, and capacitance acquisition/conversion circuitry that acquires capacitance measurements for proximal and distal self-capacitance (for example, by multi-phase capacitive charge transfer using a switched capacitor arrangement), and converts these capacitance measurements into sensor data representative of vascular pulsation.