Movable Photodiode Refractometer for Gradient Chromatography
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Solution Overview
Problem
Deflection-type refractometers have limited measurement ranges, preventing their use in gradient chromatography due to restricted differential refractive index detection, requiring a reference liquid chamber that causes instability and complexity, and are unable to provide absolute refractive index measurements.
Innovation Solution
A deflection-type refractometer with a movable position sensing detector that tracks the deflected beam, allowing for a large measurement range and enabling the detection of absolute refractive index without a reference chamber, using a light source, measuring cell with non-parallel faces, and a control unit to calculate refractive index based on beam displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed position split photodiode is used to detect beam deflection, then the device structure is simple, but the measurement range is limited
Solution Approach 1:
The patent transforms the fixed photodiode structure into a movable one. The photodiode is mounted on a movable platform that can be positioned along the beam path, allowing the detector to dynamically adjust its position to track the deflected beam across a much wider measurement range while maintaining structural simplicity through automated control.
Solution Approach 2:
The patent introduces a movable platform as an intermediary between the fixed cell and the photodiode. This platform serves as a mediator that carries the photodiode to various positions, enabling extended measurement range without requiring a complex fixed detector structure or moving the entire detection system.
2Measurement precision
If a reference liquid chamber is used in differential detection, then the refractive index can be measured, but the system becomes complex and unstable
Solution Approach 1:
The patent removes the reference liquid chamber from the system entirely. Instead of using differential detection with a reference chamber, the invention uses absolute detection where the movable photodiode directly measures the beam deflection caused by the sample liquid alone, eliminating the source of instability and complexity associated with reference liquid management.
Solution Approach 2:
The system uses the ambient air as the reference medium instead of requiring a separate reference liquid chamber. The beam passes through the sample liquid interface with air, and the deflection is measured directly. This self-service approach eliminates the need for additional reference liquid supply systems and reduces overall system complexity.
3Measurement precision
If the distance L from cell to photodiode is increased to improve sensitivity, then the measurement precision improves, but the device size increases
Solution Approach 1:
The patent makes the photodiode position dynamic rather than fixed at a large distance L. By mounting the photodiode on a movable platform that can position itself close to the cell, the system achieves high sensitivity through precise positional control rather than through a large fixed distance, thereby reducing overall device size while maintaining measurement precision.
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 solution provides a highly extended measurement range with high precision and sensitivity, enabling the detection of refractive index changes in gradient chromatography and eliminating the need for a reference chamber, thus simplifying the system and reducing instability.
Implementation Method 1
measuring cell (230) arranged such that a beam of light from the light source impinges on the measuring cell and is deflected after traversing two non-parallel faces of the measuring cell
Implementation Method 2
An optical sensor mounted on a movable platform for detecting the deflected beam of light
Data Source
AI summary
A deflection-type refractometer with extended measurement range having a light source generating a beam of light; a measuring cell with a sample chamber receiving a sample liquid; an optical sensor mounted on a movable platform for detecting the deflected beam of light; a driving unit configured to move the platform; a distance measurement unit for monitoring the displacement of the platform; a control unit configured to calculate the deflection of the beam of light based on the displacement of the platform and an output signal of the optical sensor to obtain a refractive index measure of the sample liquid using the calculated deflection.