Flow Rate Sensor Sensitivity Correction for Linearity Errors
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Solution Overview
Problem
Flow rate sensors often exhibit poor linearity due to irregularities in the processing of diverting elements, leading to errors in flow rate measurements, which cannot be accurately corrected using conventional methods, affecting the overall accuracy and yield of mass flow controllers.
Innovation Solution
A correction device and method that adjust the sensitivity of flow rate sensors by using a sensitivity correction value function to recalibrate the flow rate characteristic function, allowing for precise sensitivity adjustments and matching the sensor's characteristics to a standard function, thereby improving linearity and reducing errors across the entire range of sensor output values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard flow rate characteristic function is used without modification, then the device complexity is low, but the measurement precision deteriorates due to poor linearity and errors between calculated and actual flow rate values
Solution Approach 1:
The patent applies parameter changes by modifying the standard flow rate characteristic function through sensitivity correction values. The correction device changes the parameters of the characteristic function by multiplying it with sensitivity correction values derived from sensitivity correction value functions, thereby improving linearity and measurement accuracy without requiring complete redesign of the sensor system.
Solution Approach 2:
The patent implements preliminary action by pre-calculating and storing sensitivity correction value functions that compensate for linearity errors. These correction functions are prepared in advance based on sensitivity characteristics and are applied before actual flow rate measurements to prevent errors rather than correcting them after occurrence.
2Measurement precision
If conventional correction methods are applied to sensors with poor linearity, then the device complexity remains low, but the measurement precision worsens because flow rate errors are generated in all values except span flow rate values
Solution Approach 1:
The patent applies local quality by implementing sensitivity correction value functions that provide different correction values for different sensor output ranges. Instead of using a uniform correction factor, the system uses multiple sensitivity correction value functions (e.g., first, second, third functions) that apply appropriate correction levels based on the specific operating range, thereby improving accuracy across all flow rate values including low flow rates where conventional methods fail.
Solution Approach 2:
The patent changes the correction approach by introducing sensitivity correction values that are multiplied with the standard characteristic function. This parameter transformation converts the correction from a simple gradient adjustment to a multi-level sensitivity-based correction that addresses linearity errors throughout the entire measurement range.
3Manufacturing precision
If diverting elements with irregular processing accuracy are used, then the manufacturing precision is poor leading to non-linear sensor characteristics, but the ease of manufacture is improved by using standard processing methods
Solution Approach 1:
The patent applies self-service by enabling the sensor system to automatically compensate for its own manufacturing imperfections. The correction device uses the sensor's own sensitivity characteristics to generate sensitivity correction value functions that automatically adjust for linearity errors caused by diverting element irregularities, eliminating the need for precision manufacturing control.
Solution Approach 2:
The patent changes the approach from controlling manufacturing parameters to correcting operational parameters. Instead of attempting to control diverting element hole sizes during manufacturing, the system measures the actual sensitivity characteristics and applies mathematical corrections to the flow rate characteristic function, thereby achieving high precision despite manufacturing 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 enables precise sensitivity adjustment, improving the linearity of flow rate measurements and reducing errors, ensuring accurate flow rate control and enhancing the adjustment yield in mass flow controllers by matching the post-correction flow rate characteristic function with the actual sensor characteristics.
Implementation Method 1
a thermal flow rate sensor is formed so as to be able to measure a flow rate using the fact that a predetermined relationship exists between a flow rate and an amount of heat captured from an object
Implementation Method 2
two electrical resistance elements are provided on a flow path as a sensor mechanism, and voltage control thereof is performed such that the temperature of each electrical resistance element remains constant
Data Source
AI summary
In order to provide a correction device that enables the accuracy of the linearity between sensor output values and flow rate values in a flow rate sensor, there are provided a sensitivity correction function storage unit that stores a sensitivity correction function in which at least a portion of sensitivity correction values are set to different values in accordance with the sensor output values output from a flow rate sensor in an initial state in which the sensitivity coefficient is set to an initial value, a sensitivity setting unit that sets the sensitivity coefficient based on the initial values and on the sensitivity correction function, and then adjusts the sensitivity of the flow rate sensor, and a coefficient calculation unit that calculates a post-correction flow rate characteristic function based on function correction values that are decided in accordance with the flow rate values output post sensitivity correction.