Resistive Bridge Sensor Offset Calibration for Arterial Pulse Sensing
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Solution Overview
Problem
Existing blood pressure detection systems, particularly those using resistive bridge sensors, suffer from DC offset issues due to process variations and environmental factors, limiting their linear range and accuracy in sensing arterial pulse waveforms.
Innovation Solution
An offset calibration circuitry is implemented using successive approximation registers (SARs) and current digital to analog converters (IDACs) to compensate for the offset voltage of resistive bridge sensors, coupled with a comparator to adjust bits based on a common mode voltage, reducing power consumption during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offset calibration circuitry with SAR and IDAC is implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The offset calibration circuitry is segmented into distinct functional blocks: SAR (successive approximation register) for digital value storage, IDAC (current digital to analog converter) for current generation, comparator for voltage comparison, and switch matrix for signal routing. Each block performs a specific function in the offset calibration process, allowing for modular design and independent optimization of each component.
Solution Approach 2:
The system performs offset calibration as a preliminary action before normal arterial pulse waveform sensing operations. The SAR and IDAC components pre-calculate and store compensation values that are applied beforehand to eliminate offset errors, ensuring high measurement precision from the start of actual sensing operations without requiring continuous complex computations during normal operation.
2Measurement precision
If continuous calibration operations are performed, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The offset calibration circuitry operates periodically rather than continuously. The SAR and IDAC components perform calibration operations at predetermined intervals or under specific trigger conditions, allowing the system to maintain high measurement precision while consuming power only during calibration events rather than during entire operation periods. This periodic operation significantly reduces average power consumption compared to continuous calibration.
Solution Approach 2:
The system incorporates automatic offset calibration capability that can self-initiate calibration operations based on detected conditions or time intervals. The comparator and control logic automatically determine when calibration is needed and execute the calibration sequence without requiring external intervention, optimizing the balance between maintaining precision and minimizing power consumption through intelligent, condition-based calibration triggering.
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 system achieves accurate and efficient arterial pulse waveform sensing with reduced power consumption and a compact form factor, suitable for long-term monitoring.
Implementation Method 1
The pressure sensor may be coated with a soft biocompatible material, e.g. silicone, for comfortable skin attachment, to facilitate relatively long term monitoring. The pressure sensor may be positioned, for example, on the test subject's neck, wrist and/or finger.
Implementation Method 2
An offset calibration circuitry is implemented using successive approximation registers (SARs) and current digital to analog converters (IDACs) to compensate for the offset voltage of resistive bridge sensors
Implementation Method 3
The SAR controller circuitry is configured to adjust each bit of the first SAR and each bit of the second SAR based, at least in part, on an output of a comparator. The comparator is configured to compare a voltage on the negative voltage port or a voltage on the positive voltage port to a common mode voltage.
Data Source
AI summary
One embodiment provides an offset calibration circuitry configured to compensate an offset voltage of a resistive bridge sensor. The offset calibration circuitry includes a first current digital to analog converter (IDAC) coupled to a first successive approximation register (SAR), a second IDAC coupled to a second SAR and an SAR controller circuitry. The first IDAC is configured to couple to a negative voltage port of a resistive bridge sensor. The first SAR is configured to store a first digital value. The second IDAC is configured to couple to a positive voltage port of the resistive bridge sensor. The second SAR is configured to store a second digital value. The SAR controller circuitry is configured to adjust each bit of the first SAR and each bit of the second SAR based, at least in part, on an output of a comparator. The comparator is configured to compare a voltage on the negative voltage port or a voltage on the positive voltage port to a common mode voltage.