Thermal Sensor 3-Omega Measurement for Changing Media
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Solution Overview
Problem
Existing thermal flow sensors require calibration for specific measured media and are imprecise when operating on changing media, necessitating complex and costly procedures that interrupt ongoing measurements.
Innovation Solution
A method utilizing a 3-omega measuring technique with alternating voltage to determine thermal properties of the medium, allowing for continuous measurement by selecting a frequency that penetrates the medium at zero flow velocity, enabling simultaneous compensation for medium changes and flow velocity detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal flow sensors are calibrated for specific measured media, then measurement precision is improved, but device complexity and operational complexity increase due to required calibration procedures
Solution Approach 1:
The sensor performs self-calibration by automatically determining thermal parameters of the measured medium through 3-omega measurement during operation. The sensor element measures thermal conductivity and heat capacity without requiring external calibration equipment, allowing the system to adapt to different media automatically
Solution Approach 2:
The patent changes the measurement approach by using 3-omega measurement technique that determines thermal parameters through alternating voltage application and temperature oscillation analysis. This parameter-based approach replaces traditional calibration procedures, enabling continuous adaptation to different media without physical recalibration
2Measurement precision
If thermal flow sensors require recalibration when measured medium changes, then measurement precision is maintained, but loss of time occurs due to measurement interruptions
Solution Approach 1:
The sensor continuously determines thermal parameters of the measured medium during ongoing flow velocity measurements. The 3-omega measurement is performed continuously or periodically without interrupting the flow velocity measurement process, maintaining continuous operational capability across different media
Solution Approach 2:
The sensor performs preliminary determination of thermal parameters before flow velocity measurement to enable immediate accurate measurement. By first characterizing the medium's thermal properties through 3-omega measurement, the system prepares compensation data in advance, allowing continuous operation without interruption
3Measurement precision
If separate determination of thermal conductivity and heat capacity is performed, then measurement precision is improved, but device complexity and production costs increase
Solution Approach 1:
The patent combines the determination of thermal conductivity and heat capacity into a single integrated measurement process using one sensor element. The 3-omega measurement technique simultaneously extracts both thermal parameters from the temperature oscillation and voltage phase shift data, eliminating the need for separate measurement systems
Solution Approach 2:
The single sensor element performs multiple functions: it measures flow velocity, determines thermal conductivity, and determines heat capacity all through the 3-omega measurement technique. This multi-functional approach replaces what would traditionally require separate specialized sensors and measurement systems
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 and accurate measurement of flow velocity and medium composition without requiring prior calibration, reducing complexity and cost by using a single sensor to adapt to varying media conditions.
Implementation Method 1
the first sensor element is periodically heated by means of an alternating voltage provided in the sensor element
Implementation Method 2
a measured variable of the measured medium is determined based on a comparison of the third harmonic oscillation of the alternating voltage provided in the first sensor element with the third harmonic oscillation of temperature of the first sensor element, especially by calculating a phase shift between the third harmonic oscillation of the alternating voltage and the amplitude of the third harmonic oscillation of temperature
Implementation Method 3
As a result of flow of the measured medium around the heating element, a heat transport into the measured medium takes place, which changes with flow velocity
Data Source
AI summary
A method for operating a thermal sensor, wherein the thermal sensor includes a sensor element and an electronics, the sensor element in thermal contact with a container, in which a measured medium flows with a flow velocity, the sensor element periodically heated by an alternating voltage and, at the same time, a temperature of the sensor element is registered versus time, wherein the electronics determines a measured variable of the measured medium based on a comparison of the third harmonic oscillation of the alternating voltage with the third harmonic oscillation of the temperature, including calculating a phase shift between the third harmonic oscillation of the alternating voltage and the amplitude of the third harmonic oscillation of the temperature, and wherein a frequency of the alternating voltage is selected to achieve a penetration depth of an emitted heat of the sensor element into the measured medium at essentially zero flow velocity.