Variable Resistance Dipole for Local Electrical Resistance Measurement
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Solution Overview
Problem
Existing methods for measuring local electrical resistance of a surface face challenges in achieving a wide dynamic range while maintaining precision and speed, with solutions like logarithmic amplifiers being difficult to calibrate and transimpedance amplifiers requiring frequent gain changes, leading to measurement delays and complexity.
Innovation Solution
A measurement apparatus using a resistive measurement dipole with variable resistance, connected between a conductive probe and ground, allows for dynamic range compression through a voltage divider, enabling a wide measurement range of up to 10 or 12 decades with minimal impact on acquisition time, and includes a control device to adapt the resistance value based on measured contact resistance and a calibration resistor for easy calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If logarithmic amplifiers are used to widen measurement dynamic range, then measurement range is improved, but calibration precision and measurement accuracy deteriorate
Solution Approach 1:
The patent introduces a voltage divider circuit as an intermediary between the current source and the measurement system. This voltage divider, composed of a first resistor and a second resistor, transforms the current measurement problem into a voltage measurement problem that can be solved with high-precision voltage measurement circuits, avoiding the calibration issues of logarithmic amplifiers while achieving wide dynamic range measurement
Solution Approach 2:
The patent replaces the logarithmic amplifier (electronic system with calibration issues) with a passive voltage divider circuit combined with high-precision voltage measurement. This substitution eliminates the need for complex calibration procedures while maintaining wide measurement dynamic range capability
2Adaptability or versatility
If transimpedance amplifier with variable gain is used to measure wide resistance ranges, then measurement dynamic range is improved, but acquisition time increases due to gain changes
Solution Approach 1:
The patent segments the resistance measurement range into multiple measurement ranges, each corresponding to different combinations of the first resistor and second resistor in the voltage divider. By switching between different resistor combinations rather than using variable gain amplification, the system achieves wide dynamic range measurement without the time delays associated with gain changes
Solution Approach 2:
The patent implements dynamic switching between different resistor configurations in the voltage divider circuit based on the measured resistance value. This dynamic adaptation allows the system to maintain optimal measurement conditions across a wide resistance range while keeping acquisition time short, as the switching occurs during or between measurement cycles
3Adaptability or versatility
If logarithmic amplifiers or transimpedance amplifiers are used to achieve wide dynamic range, then measurement range is improved, but circuit complexity increases
Solution Approach 1:
The patent extracts the active amplification function from the measurement circuit and replaces it with a passive voltage divider circuit. By removing the logarithmic amplifier or transimpedance amplifier, the system achieves wide dynamic range measurement with significantly reduced circuit complexity, using only passive resistors and a simple voltage measurement circuit
Solution Approach 2:
The patent replaces complex, expensive active amplification circuits with simple, inexpensive passive resistor components. The voltage divider circuit uses basic resistors that are cheaper and more reliable than logarithmic amplifiers or transimpedance amplifiers, while achieving the same wide dynamic range measurement capability
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 apparatus achieves precise and rapid measurement of local electrical resistance over a wide dynamic range, reducing measurement uncertainty and acquisition time, while being simple to calibrate and implement, allowing for the generation of high-resolution resistance images.
Implementation Method 1
The contact resistance (to be measured) and the resistive measuring dipole (known) form a voltage divider. It is easy to demonstrate that the voltage across the terminals of the measuring dipole is a non-linear function of the contact resistance.
Data Source
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AI summary
Apparatus for measuring the local electrical resistance of a surface, comprising: a DC voltage source for applying a polarization voltage (Vp0i) to a sample (E) to be characterized; a measurement circuit (CM), that can be connected to a conducting probe that is able to come into contact with a surface (SE) of said sample, so as to generate a signal (S) representative of a contact resistance between said conducting probe and said surface of the sample; and a control device (CMD) for commanding said measurement circuit; characterized in that said measurement circuit comprises: a resistive measurement dipole (DM) exhibiting a variable resistance, connected between said conducting probe and a circuit earth; and a calculation unit (UC) for generating said signal representative of a contact resistance between said conducting probe and said surface of the sample as a function of a voltage (Vs) across the terminals of said resistive measurement dipole.