Nuclear Basis Weight Sensor Passline Correction
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Solution Overview
Problem
Basis weight sensors, particularly nuclear-based ones, face accuracy issues due to pass-line deviations caused by the fluctuating position of the moving web during measurement, leading to measurement errors.
Innovation Solution
Characterizing the pass-line behavior of the sensor as a function of sheet weight and position within the gap, using a calibration process to correct initial basis weight measurements by measuring the position of the sheet and applying a correction factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the web is unsupported in the measurement region to allow free movement, then the web can move naturally without constraint, but the web position deviates from the nominal path causing measurement errors
Solution Approach 1:
The system continuously measures the actual web position using a position sensor and feeds this information back to the control system. The control system then applies real-time corrections to the basis weight measurements based on the measured position deviations, eliminating measurement errors caused by web flutter while maintaining free web movement.
Solution Approach 2:
The system changes the measurement parameters by introducing position as an additional measured variable. By measuring both web position and radiation transmission simultaneously, and using the position information to correct the basis weight calculation, the system compensates for position-induced measurement errors without constraining web movement.
2Measurement precision
If the web position is constrained to maintain a fixed pass-line, then measurement accuracy is improved, but the web movement is restricted and natural web behavior is altered
Solution Approach 1:
Instead of physically constraining the web, the system uses feedback from position sensors to digitally correct measurements. The control system receives position data, calculates the deviation from the nominal pass-line, and applies correction factors to the basis weight measurements, achieving accuracy without mechanical constraints.
Solution Approach 2:
The system replaces mechanical position constraint mechanisms with an electronic correction system. Rather than using physical guides or supports to fix the web position, the invention uses radiation-based position sensing and computational correction to achieve the same measurement accuracy goal without mechanical interference.
3Adaptability or versatility
If calibration is performed for multiple materials and conditions, then measurement accuracy across different materials is improved, but the calibration process complexity and time increase
Solution Approach 1:
The system measures web position as an additional parameter and uses this parameter to correct basis weight measurements in real-time. By incorporating position as a correction variable, the system maintains measurement accuracy across different materials and thicknesses without requiring separate calibration procedures for each material type, as the position-based correction universally compensates for pass-line variations.
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 renders the basis weight sensor pass-line insensitive, providing accurate measurements regardless of web position fluctuations, eliminating the need for recalibration with changes in web thickness or composition, except when switching to different materials.
Implementation Method 1
A radioactive thickness/density gauge is based upon the principle that a mass of material will absorb the products of radioactive emission in a known and repeatable manner. An industrial web-gauging instrument, known as a beta-gauge, typically utilizes a radioactive isotope that decays through beta particle emission.
Implementation Method 2
The amount of radiation sensed by the detector is directly related to the amount of radiation absorbed by the web material being measured.
Implementation Method 3
measuring the position of the sheet of material within the gap
Data Source
AI summary
Nuclear-based basis weight sensors are passline-sensitive. Error in measurement is induced when the sheet moves up and down in the gap between the radiation source and detector. A passline-insensitive basis weight sensor includes a triangulation sensor to measure the position of the sheet within the gap. The sensor and gap is characterized in the laboratory for its passline behavior over a range of basis weights. The curves are either parameterized or a lookup table is created for each weight and passline position and the data added to the sensor's processor. The basis weight measured can be automatically corrected to account for deviations from the passline or nominal path through the sensor.