Intravascular Sensor Interface Circuit for High Precision Measurement
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Solution Overview
Problem
Current intravascular sensor interface circuitry is costly, physically large, and lacks high measurement accuracy due to the use of high-precision matched resistor pairs, which cannot be readily integrated into a single chip configuration.
Innovation Solution
The implementation of a single-chip interface circuit using current sources instead of resistors, with a switching unit that alternately switches between connection points to cancel temperature drift and reduce noise, providing high precision and reduced size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision matched resistor pairs are used in the sensor interface circuitry, then measurement accuracy is improved, but the physical size increases and integration into a single chip becomes difficult
Solution Approach 1:
The patent replaces the mechanical/physical resistor pair structure with an electrical equivalent circuit implementation using current sources and switching elements. This substitution allows the same measurement function to be achieved with integrated circuit components that can be fabricated on a single chip, resolving the contradiction between measurement precision and physical size.
Solution Approach 2:
The patent changes the operating parameters of the sensor interface by using current sources instead of voltage sources and implementing alternating current excitation with differential measurement. This parameter change enables high-precision measurement while allowing compact integration, as the current-based approach with switching is more amenable to integrated circuit implementation than traditional resistor-based voltage division.
2Measurement precision
If high-precision matched resistor pairs are used in the sensor interface circuitry, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent substitutes expensive, precision-matched physical resistor pairs with standard integrated circuit current sources and switching elements. These replacement components are inexpensive to manufacture using standard semiconductor fabrication processes, thereby reducing manufacturing cost while maintaining measurement accuracy through the differential measurement technique.
Solution Approach 2:
The patent employs standard, inexpensive integrated circuit components that can be mass-produced using conventional fabrication techniques, replacing the need for expensive, individually matched resistor pairs. This approach makes the sensor interface economically viable for disposable or single-use medical sensor applications.
3Measurement precision
If temperature drift compensation is implemented, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex temperature drift compensation circuits with a simplified approach using alternating current excitation and differential measurement. By switching between two measurement configurations and subtracting the signals, temperature drift and offset voltages are automatically compensated without requiring additional temperature sensors or complex compensation circuitry.
Solution Approach 2:
The patent implements periodic switching between two measurement configurations, exciting the sensor with alternating current in opposite directions. This periodic action allows the system to capture two measurements that contain equal but opposite offset voltages and temperature drift components, which are then eliminated through differential subtraction, achieving temperature compensation through time-division multiplexing.
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 achieves high measurement accuracy, reduces physical size and cost, and effectively cancels temperature drift, enhancing the precision of intravascular sensor measurements.
Implementation Method 1
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Data Source
AI summary
The present invention relates to an extracorporeale interface unit (8), for an intravascular measurement system for measuring a physiological, or other, variable in a living body, being adapted to generate a sensor signal in response of said variable. The interface unit (8) comprises a sensor interface circuitry (6) adapted to interface a sensor wire configured to be inserted into the living body and provided with one or many sensor element(s) at its distal region. The sensor interface circuitry (6) further comprises a measurement unit (9) adapted to generate the measured data of the variable as a sensor signal. The sensor interface circuitry (6) comprises two current source units (CSU1, CSU2) adapted to energize the sensor element(s) via at least two connection points (CP1, CP2, . . . CPn), and a switching unit (10), wherein the switching unit (10) is adapted to alternately switch connection between the current source units (CSU1, CSU2) and at least two of the connection points (CP1, CP2, . . . CPn), using a preset switching frequency having essentially the same connection time period (Tc) for each connection. The measurement unit (9) is adapted to determine a sensor variable value (Vdiff) related to the variable at two of the connection points (CP1, CP2, . . . CPn). The present invention further relates to a measurement system (12) comprising said extracorporeale interface unit (8) and a method in said interface unit.