Vehicle Ammeter Zero-Crossing Circuit Offset Correction
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Solution Overview
Problem
Current motor vehicle electrical systems face challenges in accurately measuring current due to zero point deviations, which can lead to significant measurement errors, especially in high-current applications and varying temperature conditions, and existing methods to correct these errors are either costly or impractical during vehicle operation.
Innovation Solution
A motor vehicle electrical system with an ammeter that includes a current sensor and a metrological zero-crossing circuit to determine zero crossings independently of models, allowing for cost-effective sensor selection and real-time correction of current measurements using a correction current value stored during zero crossings, even when the battery cannot be completely separated from consumers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensor with high measurement accuracy is used, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent applies preliminary action by determining the zero-point deviation in advance (during system initialization or calibration phase) and storing this value for subsequent correction of current measurements. This allows the use of lower-cost sensors while achieving accurate measurements through software-based correction of the pre-determined offset error.
2Measurement precision
If the battery is disconnected from loads to determine zero-point deviation, then measurement precision is improved, but ease of operation worsens
Solution Approach 1:
The system performs preliminary determination of zero-point deviation during initialization or calibration phases when the system state is known, storing this information for later use. This allows accurate offset characterization without requiring repeated disconnections during normal operation, thereby maintaining operational flexibility while achieving measurement precision.
Solution Approach 2:
The patent creates a digital copy or representation of the zero-point deviation value that can be stored and reused multiple times. Instead of physically disconnecting the battery each time measurement accuracy is needed, the system uses the stored zero-point deviation data to correct measurements during normal operation, eliminating the need for repeated operational disruptions.
3Measurement precision
If zero-point deviation is corrected using model-based estimation, then measurement precision may be improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential zero-point deviation component from the complex measurement error profile and corrects for this specific parameter in isolation. Rather than implementing complex model-based estimation that accounts for multiple error sources, the system identifies and corrects the dominant zero-offset error, significantly reducing computational complexity while maintaining practical measurement accuracy.
Solution Approach 2:
The system changes the measurement parameter by determining the zero-point deviation as a separate offset value that can be applied to correct all subsequent measurements. This parameter transformation approach simplifies the correction process compared to continuous model-based estimation, as it converts a dynamic correction problem into a static offset compensation that can be applied uniformly across the measurement range.
Data Source
Figure 1~3
Figure 4~5
AI summary
A vehicle electrical system with an ammeter for measuring the current in a line (2, 21, 31) of the electrical system. The ammeter has: - a current sensor (3, 22, 32) for measuring the current in the line (2, 21, 31) of the electrical system and for outputting a current value; and - a zero-crossing circuit (5, 23, 34) for determining a zero crossing (54a, 54b, 54c, 54d) of the current in the line (2, 21, 32).