Fluid analyzer with feedback control
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Solution Overview
Problem
Mid-infrared spectroscopy faces challenges in measuring low concentrations of analytes due to strong background absorbance, interference from background matrices, and weak, broad spectral features that are difficult to discriminate from instrumentation drifts.
Innovation Solution
A fluid analyzer system with an optical source and detector that modulates fluid flow to separate analyte and reference streams across an interrogation region, allowing for differential measurement and improved signal-to-noise ratio through lock-in amplification and digital signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If dual beam optical paths are used to measure sample and reference simultaneously, then measurement speed is improved, but optical matching complexity and device complexity increase significantly
Solution Approach 1:
The patent divides the measurement process into sequential segments: first measuring the reference channel, then measuring the sample channel. This temporal segmentation replaces the spatial segmentation of dual-beam systems, eliminating the need for complex optical matching while maintaining measurement capability.
Solution Approach 2:
The patent implements periodic switching between reference and sample measurement modes. The optical path is rapidly alternated between reference and sample channels in a periodic manner, enabling time-resolved differential measurement without requiring simultaneous dual-beam optical paths.
2Device complexity
If pseudo dual beam time method is used to alternate sample and reference cells, then device complexity is reduced, but measurement stability deteriorates due to system drift
Solution Approach 1:
The patent applies feedback control by continuously monitoring the optical path stability and dynamically adjusting measurement timing. The system measures reference and sample in rapid succession with controlled timing, using the reference measurement as a feedback baseline to correct for drift effects in the sample measurement.
Solution Approach 2:
The patent performs preliminary measurement of the reference channel before measuring the sample channel. This preliminary reference measurement establishes a baseline that accounts for current system conditions, allowing subsequent sample measurements to be differentialized against this baseline to eliminate drift effects.
3Measurement precision
If longer pathlengths are used to improve sensitivity for low concentration analytes, then measurement sensitivity is improved, but background absorbance interference worsens
Solution Approach 1:
The patent extracts the background absorbance component by measuring it separately in the reference channel (which contains only solvent without analyte). This extracted reference signal is then used to differentialize the sample measurement, effectively removing the harmful background absorbance while preserving the analyte signal.
Solution Approach 2:
The patent introduces a reference measurement as an intermediary step between the light source and sample analysis. The reference channel acts as a mediator that captures the background absorbance characteristics, which are then mathematically removed from the sample signal to reveal the pure analyte absorption features.
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
Enhances sensitivity and accuracy in measuring low analyte concentrations by canceling out background interferences and minimizing noise from instrumentation drifts, enabling longer pathlengths and more robust sampling in strongly absorbing matrices.
Implementation Method 1
Mid-infrared (Mid-IR) spectroscopy is a powerful tool for both qualitative and quantitative measurements of organic materials
Implementation Method 2
Flow-control devices conduct analyte and reference fluids through a channel and the interrogation region, and manipulate fluid flow in response to control signals to move a fluid boundary separating the analyte and reference fluids across the interrogation region
Data Source
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AI summary
There is disclosed a fluid analyzer, comprising: an optical source (16) and an optical detector (20) defining a beam path of an optical beam (24); a fluid channel with an interrogation region (22) in which the optical beam (24) interacts with a channel fluid (12); a flow-control device (18) configured to conduct, in use, a sample fluid (10) and a reference fluid (14) through the interrogation region (22), the flow-control device (18) being configured to manipulate the flow of a respective fluid in response to a fluid modulation signal; and a controller operative 1) to generate the fluid modulation signal having a time-varying characteristic to control the flow-control device (18) to operate to cause, in use, a fluid boundary separating the sample (10) and reference (14) fluids to be moved across the interrogation region accordingly, 2) to sample an output signal from the optical detector (20) at one interval of the fluid modulation signal during which the interrogation region (22) contains more sample fluid than reference fluid and at a second interval during which the interrogation region (22) contains more reference fluid than sample fluid, thereby generating corresponding output signal samples, and 3) to determine from the output signal samples a measurement value indicative of an optically measured characteristic of the sample fluid; wherein the sample fluid and the reference fluid are chosen for an optical characteristic and a fluid analyzer operating condition is adjusted in a feedback loop operative over more than one fluid modulation signal period to set the measurement value at a desired value for subsequent operation of the fluid analyzer.