Oximeter LED Verification via Forward Voltage Difference
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Solution Overview
Problem
Oximeters face challenges in accurately determining blood oxygen saturation due to manufacturing tolerances in light emitting diodes (LEDs), which can lead to incorrect measurement values when calibration information does not match the LEDs' characteristics, and relying solely on forward voltage measurements is insufficient as it can be affected by cable resistance.
Innovation Solution
A device measures the forward voltage across LEDs using both positive and negative currents to determine a calibrated difference, which is compared to a measured difference to validate the LEDs' consistency with stored calibration values, ensuring accurate oxygen saturation measurements by accounting for manufacturing tolerances and reducing the impact of cable resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If forward voltage measurement is used to verify LED characteristics, then measurement simplicity is improved, but measurement precision deteriorates due to cable resistance interference
Solution Approach 1:
The patent introduces an intermediary measurement approach by measuring voltage at multiple points (including at the LED and at the connector) and using these intermediate measurements to calculate compensated forward voltage values that eliminate cable resistance effects
Solution Approach 2:
The patent changes the measurement parameters from a single forward voltage measurement to multiple voltage measurements at different locations, and transforms the calculation from direct forward voltage to compensated forward voltage that accounts for cable resistance
2Reliability
If calibration information is stored for LED verification, then measurement reliability is improved, but device complexity increases due to additional memory and comparison circuitry
Solution Approach 1:
The patent applies preliminary action by storing calibration information in memory during device manufacturing or initial setup, so that when verification is needed, the comparison can be performed directly without requiring complex real-time calibration procedures
Solution Approach 2:
The system performs self-verification by automatically comparing measured forward voltage against stored calibration values and generating verification indicators without requiring external intervention or complex external equipment
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 method ensures that the oximeter provides accurate oxygen saturation readings by validating the LEDs' consistency with calibration values, thereby ensuring proper construction and accuracy, and reduces the complexity and cost associated with four-terminal sensing.
Implementation Method 1
a first light emitting diode and a second light emitting diode
Implementation Method 2
measure an absorption of the small beams of light to estimate oxygen saturation levels in the blood
Data Source
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AI summary
A device for measuring oxygen saturation includes circuitry configured to, while applying first current, measure a first forward voltage across the anode of the first light emitting diode and the cathode of the first light emitting diode and, while applying second current, measure a second forward voltage across the anode of the second light emitting diode and the cathode of the second light emitting diode. The circuitry is further configured to determine a measured difference of forward voltage based on a comparison of the first forward voltage and the second forward voltage and determine that the first and second light emitting diodes are valid based on a calibrated difference of forward voltage and the measured difference of forward voltage. In response to the determination that the first and second light emitting diodes are valid, the circuitry is configured to determine an oxygen saturation level.