Self-Calibrating AD Converter for Remote Accuracy Stability
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Solution Overview
Problem
Existing AD converters require external instruments for calibration, making it difficult to calibrate multiple AD converters installed at remote locations, especially due to variations in offset voltage and unit voltage over time.
Innovation Solution
An AD converter with self-calibration function that includes a reference voltage unit, a summation and conversion unit capable of summing unit voltages until a reference voltage is exceeded, and a control unit that calibrates unit voltages and offset voltage without external instruments, using a switching section, a comparator, and current sources to determine polarity and convert input voltage to digital values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If external instruments are used for calibration, then calibration accuracy can be ensured, but it becomes difficult to calibrate multiple AD converters at remote locations and requires carrying instruments
Solution Approach 1:
The AD converter performs calibration autonomously using its own internal resources (DA converter, comparator, and stored calibration data) without requiring external calibration instruments. The control unit executes calibration routines that automatically adjust the converter's characteristics, enabling field calibration at remote locations while maintaining accuracy.
Solution Approach 2:
The system creates a digital copy of calibration data in memory, replacing the need for physical reference instruments. The calibration characteristics are stored as digital values that can be recalled and used for repeated calibration operations, eliminating the need to physically transport calibration equipment.
2Reliability
If calibration is performed regularly to maintain accuracy over time, then conversion accuracy is maintained, but it requires external instruments and increases operational complexity
Solution Approach 1:
The calibration function is merged with the normal operation components of the AD converter. The DA converter, comparator, and control unit that exist for normal conversion operations are also utilized for calibration, eliminating the need for separate calibration hardware and reducing overall system complexity.
Solution Approach 2:
The existing components of the AD converter serve dual purposes: the DA converter and comparator are used both for normal conversion operations and for calibration operations. The control unit manages both conversion and calibration functions, making the system multi-functional and reducing the need for dedicated calibration hardware.
3Adaptability or versatility
If self-calibration is implemented without external instruments, then calibration at remote locations becomes feasible, but the calibration mechanism becomes more complex
Solution Approach 1:
The AD converter uses its own internal DA converter and comparator to perform self-calibration without external instruments. The control unit autonomously executes calibration routines, enabling field calibration at remote locations while the complexity is contained within the integrated circuit rather than requiring external equipment.
Data Source
AI summary
An AD converter with self-calibration function that does not require an instrument for calibration, and includes: a reference voltage unit that generates a reference voltage; a summation and conversion unit that has two or more unit voltages serving as units of amount of change in a summed voltage, and during conversion, sums up any one unit voltage of the two or more unit voltages until the summed voltage exceeds the reference voltage, with an input voltage being an initial value of the summed voltage; and a control unit including a calibration control section that calibrates the two or more unit voltages and an offset voltage of a comparator at a time of calibration, and a conversion control section that determines a polarity of the offset voltage of the comparator and thereafter converts the input voltage to a digital value during conversion.