High Resolution DAQ Calibration Using Low Res DAC
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Solution Overview
Problem
High-resolution data acquisition systems require expensive and sensitive high-resolution reference sources for calibration, making field calibration impractical and costly, as they need a reference source with at least one to two orders higher resolution than the system, which is not feasible with lower resolution digital to analog converters.
Innovation Solution
Initial calibration with a high-resolution reference source generates characteristic coefficients, and a look-up table is created to allow subsequent calibration using a lower resolution digital to analog converter, enabling field calibration of the data acquisition system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution reference source is used for calibration, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system performs preliminary calibration using a high-resolution reference source to generate characteristic coefficients and a look-up table. This preliminary action stores the high-precision calibration data, enabling subsequent calibrations to use a lower-resolution DAC without sacrificing measurement precision.
Solution Approach 2:
The invention creates a digital copy of the high-resolution reference data in the form of a look-up table stored in memory. This copy contains pre-calculated characteristic coefficients that replicate the high-resolution reference behavior, allowing the system to use a lower-resolution DAC while maintaining calibration accuracy through software-based correction.
2Measurement precision
If a high-resolution reference source is used for calibration, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The system performs preliminary calibration using a high-resolution reference source to generate characteristic coefficients and a look-up table. This preliminary action stores the high-precision calibration data, enabling subsequent calibrations to use a lower-resolution DAC without sacrificing measurement precision.
Solution Approach 2:
The invention replaces the expensive, sensitive high-resolution reference source with a lower-resolution DAC that is cheaper, more robust, and suitable for field deployment. The look-up table stored in memory serves as a digital substitute that enables the lower-resolution hardware to achieve high-resolution calibration results.
3Device complexity
If a lower resolution digital to analog converter is used, then device complexity and cost are reduced, but measurement precision deteriorates
Solution Approach 1:
The invention introduces a look-up table stored in memory as an intermediary between the lower-resolution DAC and the high-resolution measurement requirements. This look-up table contains pre-calculated characteristic coefficients that compensate for the DAC's lower resolution, enabling the system to achieve high-resolution calibration accuracy through software-based correction rather than hardware precision.
Solution Approach 2:
The system changes the operational parameters of the DAC by using non-uniform step sizes in the look-up table. The calibration process divides the measurement range into segments with different resolutions, allocating higher precision to critical measurement ranges and lower precision to less critical ranges, thereby optimizing the use of the lower-resolution DAC while maintaining overall measurement accuracy.
Data Source
AI summary
A high resolution data acquisition (DAQ) system is initially calibrated with a reference source having a resolution higher than the DAQ system. Measurements over the operating range of the DAQ system are taken, and characteristic calibration coefficients are determined from the measurements. Software corrections based upon the calibration coefficients are made to DAQ system measurements. A digital to analog converter (DAC) on-board the DAQ system having a lower resolution than the DAQ system is calibrated by generating a look-up table of input digital codewords and output electrical signals measured by the calibrated DAQ system. This look-up table is used to field calibrate the DAQ system using only the DAC, rather than the high resolution reference source.