Half Wheatstone Bridge Intraocular Pressure Sensor
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Solution Overview
Problem
Conventional intraocular pressure sensors face challenges in real-time measurement and miniaturization, leading to energy loss and power limitations, making them unsuitable for continuous monitoring of glaucoma progression.
Innovation Solution
A pressure sensing device using a half Wheatstone bridge with two variable resistors and a variable capacitor unit, employing an RC delay comparison method to generate and compare charging voltages, thereby reducing energy consumption and maintaining measurement resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional Wheatstone bridge sensor is used, then pressure measurement capability is provided, but energy loss and power consumption increase
Solution Approach 1:
The patent extracts only the necessary components from a conventional Wheatstone bridge, using a half-bridge configuration with two variable resistors instead of four. This reduction in component count minimizes the sensor size and power consumption while maintaining pressure measurement capability through the RC delay comparison method
Solution Approach 2:
The patent replaces the conventional voltage-based Wheatstone bridge measurement system with an RC delay comparison system. Instead of directly measuring voltage changes, the system uses capacitor charging/discharging time differences to encode pressure information, which reduces power consumption and enables miniaturization
2Volume of moving object
If sensor size is reduced for miniaturization, then implantability is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent substitutes direct voltage measurement with RC delay time measurement. The charging and discharging time constants of the capacitor provide a time-based encoding of pressure information that maintains measurement precision even with reduced sensor size, as the time measurement is less susceptible to size-related parasitic effects
Solution Approach 2:
The patent changes the measurement parameter from voltage amplitude to time constant. By measuring the RC delay time rather than voltage levels, the system achieves better scaling behavior for miniaturized sensors, as time constants scale more predictably with size than voltage signals are affected by parasitic capacitance and resistance changes
3Device complexity
If a full Wheatstone bridge is used, then measurement stability is improved, but device complexity increases
Solution Approach 1:
The patent extracts and uses only two variable resistors from the conventional four-resistor Wheatstone bridge configuration. The half-bridge design reduces circuit complexity while maintaining measurement stability through the RC delay comparison method, which is less sensitive to component mismatches and environmental variations
Solution Approach 2:
The patent introduces a capacitor as an intermediary element that stores energy during charging and discharging cycles. The capacitor's charge and discharge characteristics provide a stable time-based measurement reference that compensates for the reduced complexity of the half-bridge configuration, maintaining measurement stability with fewer components
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 device achieves efficient and accurate intraocular pressure measurement with reduced sensor size and power loss, ensuring reliable and continuous monitoring of glaucoma progression.
Implementation Method 1
two variable resistors of which resistance values are changed according to an environmental change
Implementation Method 2
a variable capacitor unit electrically connected to the half Wheatstone bridge unit and generating RC delays for two variable resistors, respectively
Data Source
AI summary
According to an exemplary embodiment of the present disclosure, a pressure sensing device using a sensor based on a Wheatstone bridge includes: a half Wheatstone bridge unit including two variable resistors of which resistance values are changed according to an environmental change; a variable capacitor unit electrically connected to the half Wheatstone bridge unit and generating RC delays for two variable resistors, respectively; an amplifier amplifying respective charging voltages charged after a time of the respective RC delays; and a comparator comparing the amplified charging voltages and outputting the compared charging voltages as digital values. As a result, an intraocular pressure sensing device is further miniaturized and has smaller power loss.