Digital DC Transducer Calibration via Hall Sensor
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Solution Overview
Problem
Current DC current sensors using Hall-effect sensors face issues with nonlinearity, accuracy, and temperature compensation, requiring manual calibration with trim pots and analog circuitry that is time-consuming and prone to errors.
Innovation Solution
A digitally controlled direct current transducer system incorporating an open-loop Hall-effect sensor, ADCs, a temperature sensor, a mode-selection device, and a digital processor to operate in temperature-compensated and calibration modes, eliminating the need for manual trim pot adjustments and improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If analog circuitry with trim pots is used for signal processing, then the device complexity is reduced and manufacturing cost is lowered, but measurement precision deteriorates due to ±20% tolerance and manual calibration requirements
Solution Approach 1:
The patent replaces the mechanical analog trim pot adjustment system with a digital calibration system. A digital processor reads calibration values from non-volatile memory and applies digital correction factors to the Hall sensor output, eliminating the need for physical trim pots and manual mechanical adjustment while achieving ±1% or better accuracy.
Solution Approach 2:
The patent changes the operating parameters of the Hall sensor by applying temperature compensation algorithms stored in memory. The system measures temperature with a separate sensor, retrieves pre-characterized compensation data from non-volatile memory, and applies digital correction factors to compensate for temperature-induced drift, thereby maintaining measurement precision across varying temperatures without additional analog circuitry.
2Manufacturing precision
If manual calibration with trim pots is performed, then manufacturing precision can be adjusted, but productivity deteriorates due to time-consuming calibration processes
Solution Approach 1:
The patent performs calibration actions in advance during the manufacturing process by programming digital correction values into non-volatile memory while the device is still on the production line. This preliminary digital programming replaces time-consuming post-assembly manual trim pot adjustments, enabling rapid calibration without sacrificing precision and significantly improving manufacturing throughput.
Solution Approach 2:
The system incorporates self-calibration capabilities where the digital processor automatically reads calibration parameters from non-volatile memory and applies corrections without requiring external manual intervention. This self-service approach eliminates the need for technician involvement in the calibration process, thereby improving productivity while maintaining manufacturing precision.
3Device complexity
If open-loop Hall-effect sensor is used, then device complexity is reduced compared to closed-loop, but measurement precision deteriorates due to nonlinearity
Solution Approach 1:
The patent replaces the need for complex closed-loop feedback circuitry with a digital post-processing approach. The simple open-loop Hall sensor output is read by a digital processor that applies nonlinearity correction algorithms stored in non-volatile memory, achieving linearized output without the additional analog circuitry and feedback mechanisms required by closed-loop designs.
Solution Approach 2:
The patent changes the output parameters of the Hall sensor through digital correction. Pre-characterized correction lookup tables stored in non-volatile memory contain nonlinearity compensation data that the digital processor applies to the raw sensor output, transforming the nonlinear open-loop response into a linearized measurement without modifying the sensor hardware itself.
4Device complexity
If analog circuitry is used for signal processing, then device complexity is lowered, but reliability deteriorates due to poor temperature compensation capability
Solution Approach 1:
The patent replaces analog temperature compensation circuitry with a digital implementation. A temperature sensor provides digital readings to the processor, which retrieves pre-programmed compensation factors from non-volatile memory and applies digital correction to the Hall sensor output. This digital approach provides superior temperature stability without the complexity and drift issues of analog compensation circuits.
Solution Approach 2:
The system dynamically changes the output parameter correction based on measured temperature. The digital processor continuously monitors temperature via a dedicated sensor, selects appropriate compensation factors from non-volatile memory based on the measured temperature range, and applies real-time digital correction to maintain measurement reliability across the full operating temperature range.
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 system provides increased accuracy and reduced errors by digital signal processing, allowing for easy recalibration and improved temperature compensation without the need for manual calibration, enhancing the reliability of DC current measurements.
Implementation Method 1
Many DC current sensors in the market today use Hall-effect sensors as the primary element for detecting a magnetic field generated by current flowing through the conductor. A Hall-effect sensor is a transducer that varies its output voltage in response to a magnetic field.
Implementation Method 2
A closed-loop Hall-effect sensor has a coil that is actively driven to produce a magnetic field that opposes the field produced by the current being sensed.
Data Source
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AI summary
A direct current transducer includes an open-loop Hall-effect sensor, a first ADC coupled to the open-loop Hall-effect sensor, a thermistor, a second ADC coupled to the thermistor, a manually controlled mode-selection device, a digital processor coupled to the first ADC and the second ADC, and digital memory coupled to the digital processor. The manually controlled mode-selection device is operative to develop an operating mode selection digital signal for a plurality of operating modes including a temperature- compensated direct current (DC) transducer mode and a calibration mode.