Thermal Flow Sensor Using 3-Omega Phase Shift Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thermal flow sensors require recalibration when the measuring medium changes, leading to inaccurate readings and complex, costly processes due to the need for separate determination of thermal parameters and flow velocity compensation.
Innovation Solution
A method using a 3-omega measurement with a thermal sensor that periodically heats a sensor element with an alternating voltage, determining a phase shift of the third harmonic to measure the medium's properties independently of flow velocity, allowing simultaneous compensation for medium changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal flow sensors are recalibrated when the measuring medium changes, then measurement accuracy is improved, but operational complexity and cost increase due to requiring separate calibration steps
Solution Approach 1:
The patent combines the calibration function and flow measurement function into a single integrated operation. By using the sensor element to simultaneously determine thermal parameters (through 3-omega measurement) and flow velocity, the system eliminates the need for separate calibration steps while maintaining measurement accuracy across different measuring media.
Solution Approach 2:
The sensor element serves multiple functions: it acts as both a flow measurement sensor and a calibration sensor. The same sensor element determines both the thermal parameters of the measuring medium and the flow velocity, making the system universally applicable to different media without requiring separate calibration equipment or procedures.
2Measurement precision
If thermal parameters are determined separately from flow velocity, then measurement accuracy is improved, but measurement time and operational complexity increase
Solution Approach 1:
The patent enables continuous simultaneous determination of thermal parameters and flow velocity. The sensor element continuously performs both measurement functions without interruption or sequential steps, eliminating calibration time loss while maintaining accuracy through the 3-omega measurement method integrated with flow detection.
Solution Approach 2:
The determination of thermal parameters and flow velocity is merged into a single simultaneous measurement process. The same sensor element and measurement signal are used to extract both types of information, eliminating the need for separate measurement sequences and reducing total measurement time.
3Measurement precision
If multiple sensors and electronic components are used for separate determination of thermal parameters and flow velocity, then measurement capability is improved, but production cost and device complexity increase
Solution Approach 1:
A single sensor element performs multiple measurement functions that would traditionally require separate sensors. The same sensor element determines both thermal parameters (thermal conductivity, heat capacity) and flow velocity, significantly reducing component count, manufacturing complexity, and production costs while maintaining full measurement capability.
Solution Approach 2:
The sensor element serves itself by using its own heating and sensing capabilities to determine both thermal parameters and flow characteristics. The measurement system uses the sensor's intrinsic properties and the measuring medium's interaction with it to extract multiple parameters without requiring additional dedicated components for each measurement type.
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 continuous, accurate measurement of flow velocity and medium composition without interrupting operation, reducing complexity and costs by eliminating the need for separate calibration steps.
Implementation Method 1
the first sensor element is periodically heated by means of an alternating voltage introduced into the sensor element
Implementation Method 2
a measured quantity of the measuring medium is determined by comparing the profile of the third harmonic of the alternating voltage introduced into the first sensor element with the profile of the third harmonic of the temperature of the first sensor element
Implementation Method 3
These sensors utilize the fact that a flowing medium carries away heat from a heated surface
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method for operating a thermal sensor (100), the thermal sensor (100) comprising at least a first sensor element (101) and an electronic unit (110), wherein: the first sensor element (101) is brought into thermal contact with a container (3), more particularly a pipe, through which container (3) a measurement medium (2) flows at any flow velocity; the first sensor element (101) is periodically heated by means of an alternating voltage applied to the sensor element (101), and a curve of the temperature of the first sensor element (101) is simultaneously captured; the electronic unit (110) determines a measurement variable (V3ω) of the measurement medium (2) by comparing the curve of the third harmonic oscillation of the alternating voltage applied to the first sensor element (101) to the curve of the third harmonic oscillation of the temperature of the first sensor element (101), more particularly by calculation of the phase shift between the curve of the third harmonic oscillation of the alternating voltage and the curve of the amplitude of the third harmonic oscillation of the temperature; and a frequency of the alternating voltage is selected such that the heat emitted by the first sensor element (101) penetrates into the flow profile of the measurement medium (2) with a depth of penetration (ET) in which the flow velocity of the measurement medium (2) is nearly zero. The invention also relates to a thermal sensor (100) designed to be operated by means of the method according to the invention.