Capacitor Biasing Circuit for Resistive Sensor Readout
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Solution Overview
Problem
Passive resistive sensor structures like Wheatstone bridges and Hall elements face inaccuracies due to temperature and mechanical stress variations, which affect the biasing source and the sensor itself, leading to drift in sensitivity and offset errors.
Innovation Solution
A method and circuit that utilize a capacitor to integrate and average the sensor readout signal over time, allowing the biasing current to flow through the sensor and capacitor simultaneously, enabling the determination of the total charge flow and reducing sensitivity to bias source drift, thereby improving accuracy and noise resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a constant biasing current or voltage is used to bias the resistive sensor structure, then the sensor can provide a stable output signal, but the sensitivity and offset drift due to temperature and mechanical stress variations
Solution Approach 1:
The patent measures the actual biasing current through a capacitor by integrating the current over time and using this measured value to normalize the sensor output signal. This feedback mechanism compensates for drift in the biasing current caused by temperature and stress variations, maintaining measurement precision despite changes in biasing conditions
Solution Approach 2:
The patent changes the approach from maintaining constant biasing parameters to measuring and adapting to actual biasing parameters. By measuring the actual current through capacitor integration and using this variable parameter to normalize the output, the system accommodates parameter changes rather than resisting them
2Measurement precision
If complex biasing circuits are used to maintain constant current, then temperature and stress sensitivity is reduced, but device complexity increases
Solution Approach 1:
The patent introduces a capacitor as an intermediary element that simplifies the biasing circuit. Instead of using complex constant current sources with temperature compensation, the capacitor integrates the biasing current and provides a measurable signal that can be used to normalize the output, achieving temperature independence with simpler circuitry
Solution Approach 2:
The biasing circuit uses itself to compensate for its own deficiencies. The same circuit that generates the biasing current also measures it through the capacitor integration, and uses this self-measured information to correct the sensor output, eliminating the need for external complex compensation circuits
3Device complexity
If traditional readout methods are used, then the circuit is simple, but noise resistance and Signal-to-Noise Ratio are poor
Solution Approach 1:
The patent implements continuous integration of the biasing current through the capacitor during the measurement period. This continuous action accumulates the current signal over time, improving the signal level relative to noise and enhancing the Signal-to-Noise Ratio while maintaining a relatively simple readout circuit
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 method provides a highly accurate and stable sensor readout that is less dependent on temperature and mechanical stress, allowing for the use of less complex biasing circuits and improved Signal-to-Noise Ratio, reducing the need for constant biasing current or voltage.
Implementation Method 1
biasing the resistive sensor structure by means of a biasing circuit comprising said first capacitor so as to allow or to force a biasing current through said first capacitor and through said resistive sensor structure
Data Source
AI summary
A method of biasing and reading-out a passive resistive sensor structure having two excitation nodes and two readout nodes, comprises the steps of: a) determining a first state of a first capacitor corresponding to a first amount of charge biasing the sensor structure such that a biasing current flows through said first capacitor during a first time interval determining a second state of the first capacitor corresponding to a second amount of charge integrating or averaging the readout signal during a second time interval related to the first time interval, thereby obtaining an integrated or averaged readout signal determining the sensor readout signal based on the integrated or averaged readout signal and a change in state of the first capacitor.