Optical Blood Sensor Clip with On-Clip Signal Conversion
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Solution Overview
Problem
Conventional optical blood monitoring systems during hemodialysis face issues with noise introduction and heat generation due to long cable lengths and series resistance, which degrade signal quality and reduce the lifespan of LEDs.
Innovation Solution
A sensor clip assembly with a microcontroller that processes conditioned analog signals to raw digital data, includes transimpedance amplifiers and digitally-controllable trimpots for noise filtering and gain adjustment, and features a USB output for direct data transmission to an external device, reducing noise and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If long cable lengths are used to transmit analog signals from the sensor clip assembly to the external device, then the system can be designed with separate processing units, but noise is introduced and signal quality degrades
Solution Approach 1:
The patent integrates the microcontroller, signal processing circuits, and data transmission interface directly into the sensor clip assembly housing. This merging of functions eliminates the need for long external cables and separate processing units, thereby maintaining signal quality while achieving a compact design.
Solution Approach 2:
The patent introduces a USB interface as an intermediary for digital data transmission from the sensor clip assembly to the external device. This intermediary enables short-distance digital communication, avoiding the noise issues associated with long analog cable transmissions.
2Ease of manufacture
If series resistance is used in the LED circuit, then the circuit design is simplified, but heat generation increases and LED lifespan is reduced
Solution Approach 1:
The patent replaces the conventional series resistance-based current limiting approach with a microcontroller-controlled PWM (pulse width modulation) driving scheme. This substitution allows for precise LED current control without the heat generation and lifespan reduction caused by series resistance, while maintaining ease of circuit design through software control.
3Device complexity
If analog signals are transmitted over long distances, then system components can be separated, but noise introduction degrades measurement precision
Solution Approach 1:
The patent performs preliminary analog-to-digital conversion and signal processing within the sensor clip assembly before data transmission. By converting analog signals to digital format and completing processing operations at the source, the system eliminates noise introduction during transmission and ensures high measurement precision for blood parameters.
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 solution provides accurate, real-time monitoring of hematocrit, oxygen saturation, and blood volume changes with reduced noise and extended LED lifespan by converting analog signals to digital within the sensor clip assembly, improving signal quality and operational efficiency.
Implementation Method 1
LED emitters and photodetectors for the optical blood monitor are fastened (e.g., by clipping) into place onto the blood chamber over the lenses. Multiple wavelengths of light may be resolved through the blood chamber and the patient's blood flowing through the chamber with a photodetector detecting the resulting intensity of each wavelength.
Implementation Method 2
A sensor clip assembly with a microcontroller that processes conditioned analog signals to raw digital data, includes transimpedance amplifiers and digitally-controllable trimpots for noise filtering and gain adjustment
Data Source
AI summary
Systems and sensor clip assemblies for optically monitoring blood flowing through a blood chamber are provided. A sensor clip assembly includes emitters and photodetectors positioned on opposing arms, a signal conditioning circuit for conditioning raw analog signals generated by the photodetectors while the sensor clip assembly is fastened to a blood chamber, and an analog-to-digital converter for converting the conditioned analog signals to raw digital data. The sensor clip assembly may include a microcontroller for calculating parameters of blood flowing through the blood chamber such as hematocrit, oxygen saturation, and change in blood volume from the raw digital data. The sensor clip assembly is in communication with a networked computer, and the networked computer is in communication with a remote computer configured to provide a user interface for monitoring and/or controlling the sensor clip assembly.