Chromatograph Detector Sampling Interval Adjustment
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Solution Overview
Problem
Chromatographic detectors face inaccuracies in retention time due to frequency deviations in crystal oscillators, leading to discrepancies between apparatus internal time and real time, especially over extended analysis periods, which affects the accuracy of peak retention times and user trust in the system.
Innovation Solution
A detector system that adjusts data sampling intervals dynamically to synchronize apparatus internal time with real time by using a signal generator to adjust the reference clock signal, allowing for varying data sampling intervals within a time adjustment period, and an automatic parameter-setting method using a time adjustment jig to minimize time lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed sampling period is used in the A/D converter, then the temporal resolution is maintained, but the retention time accuracy deteriorates due to crystal oscillator frequency deviation
Solution Approach 1:
The patent applies dynamics by making the data sampling interval variable rather than fixed. The sampling interval is dynamically adjusted based on the elapsed time from analysis initiation, using a sampling interval correction value that changes over time. This allows the system to compensate for crystal oscillator frequency deviation and maintain retention time accuracy without requiring complex hardware modifications.
Solution Approach 2:
The patent changes the parameter of sampling interval from a constant value to a time-dependent variable. By introducing a sampling interval correction value that varies with elapsed time, the system adjusts the sampling interval to counteract the cumulative time lag caused by frequency deviation, thereby maintaining measurement precision throughout the analysis.
2Productivity
If the sampling period is extended to reduce data load, then the CPU and memory requirements are reduced, but the temporal resolution deteriorates
Solution Approach 1:
The patent changes the sampling interval parameter from a fixed value to a dynamically adjusted value based on elapsed time. This allows the system to optimize the balance between data processing efficiency and temporal resolution by adapting the sampling interval to the specific requirements of each analysis phase, rather than using a constant interval throughout.
3Adaptability or versatility
If multiple detectors are used with independent A/D converters, then the detection capability is enhanced, but the retention time synchronization between detectors deteriorates
Solution Approach 1:
The patent introduces a feedback mechanism where the elapsed time from analysis initiation is continuously monitored and used to adjust the sampling interval. This feedback loop ensures that all detectors, regardless of their individual A/D converter characteristics, remain synchronized in terms of retention time, as the adjustment is based on the common reference of elapsed time rather than independent clock signals.
Data Source
AI summary
The present invention provides a detector for a chromatograph capable of obtaining the accurate retention time, even if there is a frequency deviation of the clock signal for determining the timing of data sampling, by conforming the progress of the detector internal time accompanied with the repetition of the sampling to that of real time. In the detector, consecutive data sampling intervals are defined to be a time adjustment period, and in one time adjustment period, each of the sampling intervals whose number is given as the interpolation value M is elongated by a predetermined number of clock counts compared to each of the other sampling intervals. If the clock signal has a positive frequency deviation, the apparatus internal time determined by the clock signal progresses faster than real time. However, providing the interpolation value M corresponding to the amount of the frequency deviation elongates the time adjustment period on the basis of the apparatus internal time, to be conformed to the time adjustment period on the basis of real time which is determined by the sampling period.