Method for self calibration of measurement nonlinearity
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Solution Overview
Problem
Existing electronic instrumentation faces challenges in maintaining linearity over time and temperature without external calibration, and requires frequent corrections, especially for faster measurements with lower accuracy, which complicates calibration and increases costs.
Innovation Solution
The instrument self-adjusts linearity by using its internal current source to measure the capacitance, eliminating source linearity errors and employing a self-calibration algorithm that accounts for dielectric absorption and integral nonlinearity, allowing for linearity adjustments without external references or multipoint calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multipoint calibration is performed to maintain measurement linearity, then measurement precision is improved, but productivity deteriorates due to reduced throughput
Solution Approach 1:
The system performs preliminary characterization of the measurement circuit's nonlinearity by measuring cardinal points (extremes and midpoints) to establish correction data in advance. This correction data is then applied during normal operation without requiring multipoint calibration, thus maintaining linearity while preserving throughput.
Solution Approach 2:
The system changes the measurement approach from multipoint calibration to cardinal point measurement, reducing the number of measurement points from multiple points across the range to just the extremes and midpoints. This parameter change in measurement strategy enables faster calibration while maintaining adequate linearity correction.
2Measurement precision
If dual converters are used to address linearity issues, then measurement precision is improved, but device complexity increases due to board space and calibration traceability
Solution Approach 1:
The measurement circuit is designed to perform multiple functions: normal measurement operation and self-calibration using its own internal resources (current source, stable time reference, and measurement circuitry). This eliminates the need for separate dual converter hardware, reducing board space and simplifying calibration traceability while maintaining linearity correction capability.
Solution Approach 2:
The measurement circuit performs self-calibration using its own internal current source and stable time reference to generate correction data without requiring external equipment or separate calibration hardware. This self-service approach reduces device complexity and board space requirements while maintaining measurement precision.
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 approach enables stable and efficient self-calibration of measurement circuits, reducing the need for external equipment and maintaining high linearity without impacting throughput, even for lower resolution, high-speed measurements.
Implementation Method 1
measuring a ramp rate of voltage across the capacitance
Implementation Method 2
measuring a ramp rate of voltage across the capacitance with a measurement circuit
Data Source
AI summary
A method for calibrating a test instrument having an initial output voltage level and an open output relay can include programming the test instrument for a certain current level, starting a timer, and stopping the timer (responsive to the test instrument entering compliance) to determine a time interval. The method can also include determining whether the time interval is within a desired range.