Thermal Flow Sensor Self-Calibration for Unknown Media
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Solution Overview
Problem
Thermal flow sensors require calibration for specific measuring media, which is inconvenient when the medium's properties are unknown, and existing self-calibration methods need prior information about the fluid's properties.
Innovation Solution
A method for calibrating thermal flow sensors by creating a basic calibration using a known medium, determining correction variables for unknown media, and compensating flow velocity measurements using thermal parameters, allowing calibration without prior knowledge of the medium's properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal flow sensors are calibrated for specific measuring media, then measurement precision is improved, but device complexity and ease of operation deteriorate due to requiring special calibration setups and reference sensors
Solution Approach 1:
The thermal flow sensor performs self-calibration by automatically determining its own thermal parameters through measurement of the measuring medium's thermal properties. The sensor uses its heating element and temperature sensors to measure thermal conductivity and heat capacity of the medium, then applies these measurements to compensate for thermal parameter variations and calculate accurate flow velocity without external calibration equipment.
Solution Approach 2:
The sensor incorporates feedback mechanisms where measured thermal parameters of the measuring medium are used to adjust and compensate the flow velocity calculation. The system continuously monitors thermal properties and uses this information to correct measurement deviations, ensuring accurate flow velocity determination across different media types.
2Measurement precision
If thermal flow sensors require calibration for each measuring medium, then measurement precision is improved, but loss of time increases due to recalibration requirements when medium changes
Solution Approach 1:
The sensor automatically performs calibration for each measuring medium without requiring manual intervention or external calibration equipment. When the medium changes, the sensor simply measures the new medium's thermal parameters and adjusts its calibration accordingly, eliminating the need to send the sensor to a calibration facility.
Solution Approach 2:
The sensor performs preliminary measurement of the measuring medium's thermal parameters before using it for flow velocity measurement. By determining thermal conductivity and heat capacity in advance, the sensor prepares the necessary calibration data beforehand, allowing immediate accurate measurement without time-consuming recalibration procedures.
3Ease of operation
If existing self-calibration methods are used, then ease of operation is improved, but measurement precision deteriorates because prior information about fluid properties is required
Solution Approach 1:
The sensor determines its own thermal parameters by measuring the measuring medium's thermal properties directly. Instead of relying on pre-provided fluid property information, the sensor uses its heating element and temperature sensors to measure thermal conductivity and heat capacity, then uses these measured values to compensate for thermal parameter variations and calculate accurate flow velocity.
Solution Approach 2:
The patent replaces the need for mechanical or manual calibration procedures with an automated thermal measurement system. The sensor uses electrical heating and temperature sensing to measure thermal parameters, substituting manual calibration operations with automated thermal property measurement and computational compensation.
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 user-calibrated thermal flow sensors to operate accurately with any medium without special setups or reference sensors, allowing for flexible and efficient deployment in various applications.
Implementation Method 1
As the medium flows around the heating element, heat is transferred into the medium, and this transfer changes with the flow velocity
Implementation Method 2
a flowing medium carries away heat from a heated surface
Data Source
Figure 1~2
AI summary
The invention relates to a method for operating a thermal flow sensor (100), the thermal flow sensor (100) having at least one sensor element (101, 102, 103) and an electronic unit, the method comprising: - creating a basic calibration of the thermal flow sensor (100), wherein the thermal flow sensor (100) senses at least one flow speed of a first measurement medium and creates a measured value of the flow speed during the creation of the basic calibration, wherein the first measurement medium has defined first thermal parameters, in particular a first thermal conductivity and/or a first thermal capacity and flows with at least one defined value of a flow speed, and wherein the basic calibration causes the value, created by the thermal flow sensor (100), of the flow speed of the first measurement medium to be adjusted to the defined value of the flow speed of the first measurement medium; - determining second thermal parameters, in particular a second thermal conductivity and/or a second thermal capacity, of a second measurement medium (2) by means of the thermal flow sensor (100); - calculating a correction variable, wherein the correction variable compensates deviations between the second thermal parameters of the second measurement medium (2) and the first thermal parameters of the first measurement medium (2); and - sensing the flow speed of the second measurement medium (2) and creating flow speed measured values compensated by means of the correction variable. The invention also relates to a thermal flow sensor.