Adaptive A/D Resolution in Process Variable Transmitters
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Solution Overview
Problem
Conventional process variable transmitters set A/D converters to a fixed resolution, leading to suboptimal measurement accuracy as the input signal often operates within a narrower range than the full sensor range, resulting in unnecessary resolution errors.
Innovation Solution
The transmitter dynamically adjusts the resolution of the A/D converter based on the measured signal level, normalizing the input signal or adjusting the voltage reference to maintain optimal resolution zones, ensuring the converter operates at the highest possible resolution for the given signal range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the configurable resolution gain adjustment is set for a single, fixed resolution to accommodate the entire sensor range, then the A/D converter can measure the full range of the sensor, but the measurement circuit is not tuned to use the full capability of the A/D converter resulting in suboptimal measurement accuracy
Solution Approach 1:
The patent implements dynamic resolution adjustment by monitoring the actual input signal level and automatically changing the A/D converter resolution setting to match the signal range being measured. This allows the system to transition from a static fixed-resolution configuration to a dynamic adaptive configuration that optimizes measurement precision for the current operating conditions while maintaining the ability to cover the full sensor range when needed.
Solution Approach 2:
The system changes the resolution parameter of the A/D converter based on the measured signal level. By adjusting the resolution setting (a key parameter) according to the actual signal conditions, the system achieves optimal measurement accuracy for the current signal range while preserving the capability to measure across the entire sensor range when the signal requires it.
2Measurement precision
If the A/D converter is set to high resolution for narrow signal ranges, then measurement accuracy is improved, but the converter cannot accommodate the full sensor range
Solution Approach 1:
The system dynamically adjusts the A/D converter resolution setting based on the actual input signal level. When the signal is within a narrow range, the resolution is increased to maximize measurement precision. When the signal approaches the full sensor range, the resolution is adjusted downward to accommodate the broader range, thus achieving both high resolution when needed and full range coverage when required.
Solution Approach 2:
The resolution parameter of the A/D converter is changed based on the measured signal level. This parameter adjustment allows the system to optimize for high resolution when the signal is confined to a narrow range, while maintaining the capability to cover the full sensor range when the signal expands, thereby resolving the contradiction between resolution and range coverage.
3Adaptability or versatility
If the configurable resolution gain adjustment is set to accommodate the full sensor range, then the A/D converter can measure any signal level, but resolution errors increase when the signal operates within a narrower range
Solution Approach 1:
The system implements automatic resolution optimization by continuously monitoring the input signal level and adjusting the A/D converter resolution setting accordingly. This dynamic adjustment eliminates resolution errors that would occur with a fixed high-range setting by tailoring the resolution to the actual signal conditions, while maintaining the capability to accommodate the full sensor range when necessary.
Solution Approach 2:
The system uses feedback from the measured signal level to automatically adjust the resolution setting. By feeding back information about the actual signal conditions to the resolution control mechanism, the system can optimize measurement precision for the current operating point while preserving the ability to cover the full sensor range when the feedback indicates it is necessary.
Data Source
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AI summary
A process variable transmitter (10) is used to measure a process variable, and, in doing so, dynamically changes the resolution of the A/D converter (18) based upon the measured value of the analog input signal. This can be done by automatically adjusting the configurable resolution gain adjustment based on the value of the analog signal being measured, by normalizing the input signal being measured so that it is centered in an optimal resolution window of the A/D converter (18), or by adjusting a voltage reference provided to the A/D converter (18).