Thermal Flowmeter Logarithmic Calibration
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Solution Overview
Problem
Thermal type flowmeters face challenges in determining the correlation between sensor values and actual flow rates due to variations among products and environmental factors, requiring numerous adjustment points and time-consuming calibration processes.
Innovation Solution
A thermal type flowmeter with a sensor and flow-rate calculating unit that uses a logarithmic equation (sensor value = transformation coefficient A × log(flow rate)^2 + transformation coefficient B × log(flow rate) + transformation coefficient C) to calculate flow rates, allowing for quicker determination of the correlation between sensor values and actual flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the correlation between sensor value and flow rate is determined using traditional calibration methods with multiple adjustment points, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent transforms the calibration problem by changing the mathematical parameter representation. Instead of using the traditional linear relationship between sensor value and flow rate, it applies a logarithmic transformation where log(flow rate) becomes the independent variable. This parameter change allows the calibration data to be fitted to a straight line using least squares method, significantly reducing the number of required calibration points and calibration time while maintaining measurement precision.
2Stability of the object's composition
If the heater temperature difference is maintained at a constant value, then measurement stability is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the heater is controlled to maintain a constant temperature difference between the heater and the fluid. The temperature difference detection unit continuously monitors the temperature difference, and this information is fed back to adjust the heater power, ensuring the temperature difference remains at the predetermined value. This feedback loop stabilizes the measurement conditions while managing the control complexity through a straightforward control strategy.
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
This approach enables the correlation between sensor values and actual flow rates to be determined in a short time, reducing the need for extensive calibration points and improving measurement efficiency.
Implementation Method 1
measures the flow rate of a fluid using the effect of thermal diffusion in the fluid
Implementation Method 2
measures the flow rate from a difference in temperature between the upstream and downstream sides of the heater
Data Source
AI summary
A thermal type flowmeter includes a sensor and a flow-rate calculating unit. The sensor includes a heater that heats a fluid to be measured. The sensor is configured to output a sensor value corresponding to a state of thermal diffusion in the fluid heated by the heater which is being driven in such a manner that a difference between a temperature of the heater and a temperature of the fluid at a location free from thermal influence of the heater is equal to a predetermined temperature difference. The flow-rate calculating unit is configured to calculate a flow rate of the fluid from the sensor value by using a flow-rate calculation equation, “sensor value=transformation coefficient A×log (flow rate)2+transformation coefficient B×log (flow rate)+transformation coefficient C”.