AD Conversion Timing With Non-Integer Sampling Interval Correction
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Solution Overview
Problem
Analog/digital conversion systems in medical imaging, such as X-ray CT scanners, face errors due to voltage threshold exceedance and noise issues, particularly when input voltages approach the maximum range, leading to measurement errors and uneven sampling intervals.
Innovation Solution
The system adjusts sampling timing by performing the N-th sampling at a timing when the interval between the (N-1)-th and N-th samples is equal to the sampling period multiplied by a predetermined coefficient k, set to a non-integer value to minimize detection value errors, allowing for precise analog/digital conversion even when measurement periods do not correspond to sampling periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sampling is performed at fixed intervals using an AD converter with limited dynamic range, then high-intensity radiation can be converted into digital signals, but measurement errors increase when input voltage approaches the maximum range
Solution Approach 1:
The patent applies dynamics by making the sampling interval variable rather than fixed. The sampling interval is dynamically adjusted based on the measured voltage level - when voltage is low, shorter intervals are used; when voltage approaches maximum range, longer intervals are used. This dynamic adaptation resolves the contradiction by preventing measurement errors at high voltage levels while maintaining efficient sampling at lower levels.
Solution Approach 2:
The patent changes the parameter of sampling interval based on voltage level conditions. By monitoring the voltage level and adjusting the sampling interval parameter accordingly, the system optimizes measurement accuracy across the full dynamic range of the AD converter, preventing the detection value errors that occur with fixed-interval sampling.
2Productivity
If the sampling interval is extended to cover the entire measurement period, then fewer sampling operations are needed, but detection value errors increase when voltage exceeds the threshold
Solution Approach 1:
The system dynamically adjusts sampling intervals based on real-time voltage conditions. Rather than using a single extended interval, the system switches between shorter and longer intervals depending on whether voltage is below or above the threshold, maintaining both efficiency and accuracy.
Solution Approach 2:
The patent implements periodic sampling with variable periods. The sampling operation repeats periodically, but the interval between repetitions changes based on voltage level - shorter periods when voltage is low, longer periods when voltage is high. This periodic action with variable timing resolves the contradiction between productivity and measurement precision.
3Ease of operation
If fixed sampling periods are used regardless of voltage level, then the sampling process is simple and efficient, but measurement errors occur when input voltage is high
Solution Approach 1:
The patent transitions from static fixed sampling to dynamic adaptive sampling. The sampling process automatically adjusts its characteristics based on voltage level, maintaining simplicity of operation while eliminating measurement errors through condition-based interval selection.
Solution Approach 2:
The system uses feedback from voltage level measurements to control sampling interval selection. The measured voltage feeds back into the sampling control logic, which then adjusts the appropriate interval to use. This feedback mechanism maintains operational simplicity while ensuring measurement precision across all voltage conditions.
Data Source
AI summary
In order to provide a highly precise analog/digital conversion system in which an output error of an AD converter is small, sampling is performed at a certain sampling period S from the start time of a measurement period TL to the (N−1)-th sampling when the measurement period TL does not correspond to the sampling period S multiplied by the number of samplings N, the N-th sampling is performed at a timing when a time interval between the (N−1)-th sampling and the N-th sampling is equal to the sampling period S multiplied by a predetermined coefficient k, and the k value is set to a non-integer optimum value evaluated in advance in accordance with the N value in order to minimize an error of the detection value of the AD converter.