DC Voltage Measurement Using Standard Voltage Source Calibration
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Solution Overview
Problem
Current methods for measuring DC voltage in motor vehicle batteries, such as those with 'stop and start' systems, face precision issues due to the spread of reference voltage in analog-to-digital converters, leading to measurement errors greater than ±240 mV, and existing solutions to improve precision are costly and ineffective in addressing temperature drift in level adapters.
Innovation Solution
A method and device that utilize a standard voltage source to correct for reference voltage variations by converting the DC voltage into a digital value using an analog-to-digital converter with a specific proportionality factor, and incorporating a digital calibration procedure to account for initial tolerances, along with a multiplexer to alternate between battery and standard voltage signals, reducing errors and increasing precision to ±200 mV without significant cost increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional voltage regulator is used to provide reference voltage to the analog-to-digital converter, then the device complexity and cost are kept low, but the measurement precision deteriorates due to reference voltage spread of approximately ±2%, resulting in measurement errors of approximately ±240 mV
Solution Approach 1:
The patent introduces a standard voltage source as an intermediary reference that is more stable and precise than the conventional voltage regulator output. This standard voltage source serves as a mediator between the measurement system and the reference requirement, providing a stable reference without requiring complex voltage regulation circuitry. The standard voltage source is used to calibrate the measurement system, thereby improving precision without significantly increasing device complexity.
Solution Approach 2:
The patent implements a feedback mechanism by measuring the actual voltage from the standard voltage source and using this information to calculate a correction factor. This correction factor is then applied to the measurements taken by the analog-to-digital converter. The feedback loop continuously monitors and adjusts the reference voltage effectively, compensating for variations and improving measurement precision without requiring a complex voltage regulator.
2Measurement precision
If reduced tolerance components are used to produce the level adapter, then the measurement precision is improved, but the manufacturing cost increases by a factor greater than 5 and the temperature drift coefficient cannot be completely protected against
Solution Approach 1:
The patent uses a standard voltage source as an intermediary reference that is more stable and precise than the conventional voltage regulator output. This standard voltage source serves as a mediator between the measurement system and the reference requirement, providing a stable reference without requiring complex voltage regulation circuitry. The standard voltage source is used to calibrate the measurement system, thereby improving precision without significantly increasing device complexity.
Solution Approach 2:
The patent changes the reference voltage parameter from a regulated voltage (which has spread and temperature drift) to a standard voltage from a standard voltage source (which has known, stable characteristics). This parameter change fundamentally alters the reference stability, improving measurement precision without requiring expensive reduced tolerance components in the level adapter. The correction factor calculated from the standard voltage source compensates for any remaining variations.
3Measurement precision
If the reference voltage spread is reduced to meet the ±200 mV precision requirement, then the measurement precision is improved, but the cost of the voltage regulators and electronic modules increases considerably
Solution Approach 1:
The patent introduces a standard voltage source as an intermediary reference that is more stable and precise than the conventional voltage regulator output. This standard voltage source serves as a mediator between the measurement system and the reference requirement, providing a stable reference without requiring complex voltage regulation circuitry. The standard voltage source is used to calibrate the measurement system, thereby improving precision without significantly increasing device complexity.
Solution Approach 2:
The patent implements a feedback mechanism by measuring the actual voltage from the standard voltage source and using this information to calculate a correction factor. This correction factor is then applied to the measurements taken by the analog-to-digital converter. The feedback loop continuously monitors and adjusts the reference voltage effectively, compensating for variations and improving measurement precision without requiring a complex voltage regulator.
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 solution achieves precise DC voltage measurement with reduced errors, meeting the requirements of 'stop and start' systems while maintaining reasonable costs by using a moderate-cost voltage standard and digital calibration, effectively correcting for reference voltage and level adapter variations.
Implementation Method 1
converting the DC voltage into a digital value by means of an analog-to-digital converter with which a reference voltage is associated
Implementation Method 2
delivering, to the analog-to-digital converter, a standard voltage coming from a standard voltage source
Implementation Method 3
computing a digital value representing the digital value of the voltage, such that: Ncor=Co×(Nbat/Nvo)
Data Source
AI summary
A method for measuring a DC voltage such as the voltage Vbat of a motor vehicle battery, according to which the voltage Vbat is converted into a digital value Nbat by an analog-to-digital converter (3) with which a reference voltage Vref is associated. A standard voltage Vo coming from a standard voltage source (11) is, furthermore, delivered regularly to the analog-to-digital converter, and the voltage Vo is converted into a digital value Nvo, then a digital value Ncor representing the value of the voltage Vbat is computed, such that Ncor=Co×(Nbat/Nvo), where Co=Ncor_max×(2N/Vbat_max)×(Vo/Vref), Ncor_max being a value selected for coding the maximum value of Ncor, Nbat_max a digital value resulting from the conversion of the maximum voltage Vbat_max to be measured, and N the number of bits of the analog-to-digital converter.