Biological Sensor DC Noise Removal for Oxygen Saturation Accuracy
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Solution Overview
Problem
Conventional photoplethysmographic sensors face challenges in maintaining a high signal-to-noise ratio due to external light interference, leading to saturation issues and reduced accuracy in oxygen saturation measurements.
Innovation Solution
A biological sensor design that includes a microcontroller with a driving signal generator, a light-emitting element, a light-receiving element, and an amplifying circuit with an offset unit, which converts and amplifies current detection signals, reducing DC noise by applying a pulse-form offset voltage synchronized with the driving signal, thereby improving the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amplification rate of the amplifier is reduced to prevent output saturation caused by external light DC noise, then the saturation problem is avoided, but the amplitude of the pulsation component drops and the accuracy of oxygen saturation detection decreases
Solution Approach 1:
The patent extracts and removes the DC noise component caused by external light interference through a DC blocking capacitor in the signal processing circuit. This separates the useful AC pulsation signal from the harmful DC noise, allowing the amplifier to operate at high gain without saturation while maintaining accurate detection of the pulsation component for oxygen saturation calculation.
Solution Approach 2:
The patent introduces a DC blocking capacitor as an intermediary element between the photodiode and the amplifier. This capacitor acts as a mediator that blocks the DC noise component from reaching the amplifier while allowing the AC pulsation signal to pass through, enabling the amplifier to amplify the signal without being saturated by DC noise.
2Measurement precision
If the amplification rate of the amplifier is increased to improve the signal to noise ratio, then the detection sensitivity improves, but the output saturation occurs when external light DC noise increases
Solution Approach 1:
The patent extracts and removes the DC noise component caused by external light interference through a DC blocking capacitor in the signal processing circuit. This separates the useful AC pulsation signal from the harmful DC noise, allowing the amplifier to operate at high gain without saturation while maintaining accurate detection of the pulsation component for oxygen saturation calculation.
Solution Approach 2:
The patent introduces a DC blocking capacitor as an intermediary element between the photodiode and the amplifier. This capacitor acts as a mediator that blocks the DC noise component from reaching the amplifier while allowing the AC pulsation signal to pass through, enabling the amplifier to amplify the signal without being saturated by DC noise.
3Ease of operation
If external light enters the light-receiving element and combines with the detection signal, then the light reception output includes both signal and noise components, but the signal to noise ratio drops due to DC noise from external light
Solution Approach 1:
The patent extracts and removes the DC noise component caused by external light interference through a DC blocking capacitor in the signal processing circuit. This separates the useful AC pulsation signal from the harmful DC noise, allowing the amplifier to operate at high gain without saturation while maintaining accurate detection of the pulsation component for oxygen saturation calculation.
Solution Approach 2:
The patent introduces a DC blocking capacitor as an intermediary element between the photodiode and the amplifier. This capacitor acts as a mediator that blocks the DC noise component from reaching the amplifier while allowing the AC pulsation signal to pass through, enabling the amplifier to amplify the signal without being saturated by DC noise.
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 enhances the signal-to-noise ratio of the detection signal, allowing for higher amplification rates without saturation, improving the accuracy of oxygen saturation measurements and reducing power consumption while maintaining robustness against variations in skin conditions and body movement.
Implementation Method 1
a light-emitting element that emits light in accordance with the driving signal
Implementation Method 2
a light-receiving element that outputs a current detection signal based on an intensity of received light
Implementation Method 3
an amplifying circuit that converts the current detection signal into a voltage detection signal, amplifies an alternating current component of the voltage detection signal, and outputs an amplified detection signal
Data Source
AI summary
A biological sensor capable of improving the signal to noise ratio of a detection signal obtained by a light-receiving element and amplified by an amplifier is provided.The biological sensor includes a microcontroller that generates a driving signal, a light-emitting element that emits light in accordance with the driving signal, a light-receiving element that outputs a current detection signal based on an intensity of received light, and an amplifying circuit that converts the current detection signal into a voltage detection signal, amplifies an alternating current component of the voltage detection signal, and outputs an amplified detection signal. Furthermore, the microcontroller generates an offset signal that is applied to an offset circuit to offset the direct current component of the voltage detection signal and to obtain biological information by processing the amplified detection signal.