Thermal Flow Meter with Three-Sensor Diagnostic and Error Correction
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Solution Overview
Problem
Existing thermal flowmeters face challenges in accurately determining mass flow rate and flow direction simultaneously, especially at varying flow rates and in the presence of sensor drift or coating formation, leading to measurement errors.
Innovation Solution
A thermal flowmeter with at least three sensor elements and an electronics unit that allows continuous determination of mass flow rate and flow direction, while also diagnosing sensor states and correcting for malfunctions or coating formation, using adjustable heating power and separate control units for each sensor element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only two sensor elements are used in the flowmeter, then the device complexity is reduced, but the ability to simultaneously determine mass flow rate, flow direction, and diagnose sensor states is compromised
Solution Approach 1:
The flowmeter uses three sensor elements instead of two, segmenting the measurement function into distinct components: two sensors for flow rate and direction determination, and one sensor for diagnostic purposes. This segmentation allows simultaneous flow measurement and sensor state monitoring without compromising either function.
2Measurement precision
If sensor elements are heated continuously to maintain temperature difference, then mass flow rate measurement is improved, but sensor drift and coating formation occur leading to measurement errors
Solution Approach 1:
The system performs preliminary diagnostic checks by comparing measurements from multiple sensor elements before final flow rate determination. This preliminary action detects sensor drift or coating formation early, allowing correction or rejection of affected sensor data before it compromises the measurement.
Solution Approach 2:
The flowmeter continuously monitors sensor element states by comparing measurements across all three sensors. When drift or coating formation is detected in one sensor, the system provides feedback to adjust or replace that sensor's data with readings from other sensors, maintaining measurement reliability.
3Measurement precision
If multiple sensor elements are used for flow direction detection, then flow direction determination is improved, but the device complexity and cost increase
Solution Approach 1:
Each sensor element serves multiple functions: they all contribute to flow rate determination, flow direction detection, and mutual diagnostic verification. The third sensor element is particularly valuable as it provides redundant measurement capability and enables diagnostic functions without requiring separate dedicated sensors for each purpose.
4Adaptability or versatility
If heating power is increased to maintain temperature difference at higher flow rates, then mass flow rate measurement range is extended, but energy consumption and sensor drift increase
Solution Approach 1:
The heating power supplied to sensor elements is dynamically adjusted based on the measured flow rate. At higher flow rates where more heating power is needed to maintain temperature difference, the system monitors sensor states more closely and uses multiple sensors to distribute the measurement function, reducing the heating burden on individual sensors and thereby reducing overall energy consumption and drift.
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 mass flow rate and flow direction, while simultaneously diagnosing sensor states and correcting for errors, thereby improving measurement accuracy and reliability.
Implementation Method 1
the heat is derived from the active temperature sensor via heat conduction, thermal radiation and possibly also over free convection within the medium
Implementation Method 2
there is an additional cooling of the active temperature sensor by the pebble medium flowing past. An additional heat transport occurs due to forced convection
Implementation Method 3
an additional resistance heating can be integrated within the respective sensor element. Alternatively, however, the temperature sensor can also itself as a resistance element, for. B. in the form of an RTD resistor element
Implementation Method 4
the at least two sensor elements are introduced into a pipeline flow through a fluidized medium at least temporarily and partially flowed through, such that they are in thermal contact with the medium
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a thermal flow meter (1), in particular for determining and/or monitoring the mass flow rate (ΦΜ) and/or the flow velocity (vD) of a flowable medium (3) through a pipeline (2), comprising at least three sensor elements (4a, 4b, 4c) and an electronics unit (9), and to a method for operating a thermal flow meter (1), wherein each of the at least three sensor elements (4a, 4b, 4c) is in thermal contact with the medium (3) at least partially and/or at times and comprises a heatable temperature sensor (5a, 5b, 5c), wherein the electronics unit (9) is designed to heat each of the three sensor elements (4a, 4b, 4c) with a heating power (P1, P2, P3), to sense the temperature (T1, T2, T3) of each of the heating elements, and to heat at least two of the at least three sensor elements (4a, 4b, 4c) simultaneously, to continuously determine the mass flow rate (ΦΜ) and/or the flow velocity (vD) of the medium (3), and to simultaneously make a statement about the state (D1, D2, D3) of at least one of the at least three sensor elements (4a, 4b, 4c) on the basis of a comparison of the temperatures (T11, T12, ...) and/or heating powers (P11, P12, ...) in pairs, and, if a malfunction and/or formation of a coating occurs at at least one of the at least three sensor elements (4a, 4b, 4c), to perform a correction of the measured value for the mass flow rate (ΦΜ) and/or the flow velocity (vD) and/or to generate and output an indication of the state of the at least one sensor element (4a, 4b, 4c).