In-Line Optical Sensor Calibration Unit with Moveable Filters
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Solution Overview
Problem
Conventional in-line optical sensors require periodic calibration and often need to be removed from the process for calibration, which is inconvenient due to size or cost constraints, and may not have built-in calibration filters, necessitating frequent replacement or manual filter movement.
Innovation Solution
A calibration unit with a housing containing two moveable National Institute of Standards and Technology traceable neutral-density filters, allowing for in-situ calibration without removing the sensor, featuring rotatable filters and actuators for automated movement, enabling reversible attachment to the flow cell, light source, and detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional in-line optical sensors are used without built-in calibration filters, then cost and size constraints are satisfied, but the sensors require removal from the process for calibration which disrupts operation
Solution Approach 1:
The patent combines the calibration filters with the flow cell assembly, integrating the calibration function directly into the sensor housing. This merging allows calibration to be performed in-situ without removing the sensor from the process, thus maintaining process continuity while enabling convenient calibration operation.
Solution Approach 2:
The flow cell assembly is designed to serve multiple functions: it acts as both the process measurement chamber and the housing for calibration filters. The filter assembly can be used for both calibration purposes and as a flow cell spacer, providing multi-functionality that eliminates the need for separate calibration components and enables in-situ calibration.
2Extent of automation
If manual filter movement is used for calibration, then device complexity is reduced, but calibration time and labor requirements increase
Solution Approach 1:
The patent employs a rotatable filter assembly that can dynamically move between different positions (calibration position and flow cell position) through rotation. This dynamic mechanism allows automated positioning of filters during calibration sequences, reducing manual intervention time while maintaining relatively simple device structure through the use of a single rotational degree of freedom.
3Measurement precision
If ND filters are exposed to the optical beam frequently, then calibration accuracy is maintained, but filter deterioration increases requiring more frequent replacement
Solution Approach 1:
The patent extracts the calibration filters from continuous exposure to the optical path by positioning them in a separate filter assembly that can be rotated into the beam path only during calibration. This extraction from continuous exposure reduces cumulative light-induced deterioration while maintaining calibration accuracy when the filters are positioned in the beam during calibration sequences.
Solution Approach 2:
The filter assembly is designed to be positioned in the optical path periodically only during calibration sequences rather than continuously. The rotatable mechanism allows the filters to be inserted into the beam path temporarily for calibration measurements and then rotated out of the path during normal operation, reducing total exposure time and extending filter service life while maintaining measurement precision during calibration events.
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
Enables convenient and flexible calibration of in-line optical sensors within the process, reducing the need for frequent sensor replacement and manual operations, allowing for accurate monitoring of process parameters without disrupting the process setup.
Implementation Method 1
One common calibration method uses neutral density (ND) optical filters of known absorption positioned at any point in the optical path between the light source and detector of the sensor. Such ND filters allow only a known portion of the light form the light source, which is associated with a particular absorption (or transmission) value by the detector.
Data Source
AI summary
A device for calibrating an in-line sensor is disclosed, including a housing having a first aperture and a second aperture arranged along an optical path extending through the housing, a first filter and a second filter disposed within the housing such that the filters are moveable from an operating position to a calibration position. In the calibration position the filters are arranged in the optical path and the housing includes a connection adjacent each of the first aperture and the second aperture, the connection structured to enable the housing to be reversibly attached to a flow cell, a detector and a light source of an in-line sensor.