Flow Sensor Drift Detection via Segmented Resistors
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Solution Overview
Problem
Existing mass flow sensors in gas-air ratio control systems for heaters face challenges in reliably detecting sensor drift and heat transfer impairments, leading to incorrect measurements due to contamination or defects, which are not effectively addressed by current methods.
Innovation Solution
A flow sensor design with three temperature-sensitive resistors (R1, R2, R3) connected in parallel, where each resistor can be heated and measured to ensure correct functionality and heat transfer, using a method that involves switching between heating and temperature measurement modes to detect any deviations in temperature readings, thereby ensuring sensor plausibility and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mass flow sensor is used in a gas-air ratio control system, then the combustion quality can be regulated, but sensor drift and heat transfer impairments lead to incorrect measurements
Solution Approach 1:
The sensor is divided into multiple independent temperature-sensitive resistors (at least three: first, second, and third resistors) that can be independently heated and measured. This segmentation allows individual monitoring of each resistor's temperature and heat transfer characteristics, enabling detection of drift or impairment in specific components without affecting the entire sensor's functionality.
Solution Approach 2:
The patent implements a feedback mechanism where the actual temperatures of the resistors are continuously measured and compared against expected values during operation. This feedback loop enables real-time detection of sensor drift or heat transfer impairments, allowing the system to identify when measurements become unreliable and take appropriate action.
2Reliability
If the sensor is checked for zero flow during operation, then safety can be ensured, but defined mass flows cannot be determined to verify sensor plausibility
Solution Approach 1:
The patent performs preliminary functional checks of the sensor during operation by heating and measuring the temperatures of the resistors while mass flow is present. This preliminary action verifies that the sensor components are functioning correctly and heat transfer is proper before relying on mass flow measurements, enabling plausibility verification without requiring zero flow conditions.
3Productivity
If temperature-sensitive resistors are heated during operation, then mass flow can be measured, but heat transfer impairments or drift cannot be detected
Solution Approach 1:
The patent merges the mass flow measurement function with the sensor functionality check by simultaneously heating the resistors for mass flow measurement and measuring their temperatures to verify proper heat transfer. This combination allows both productivity (continuous measurement) and reliability (functional verification) to be achieved without separate operations.
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 solution allows for reliable detection of sensor drift and heat transfer issues, ensuring accurate mass flow measurements by comparing temperatures across resistors and enabling functional testing both for flowing and stationary media without requiring redundant sensors or significant structural changes.
Implementation Method 1
three temperature-sensitive electrical resistors (R1, R2, R3) connected in parallel
Implementation Method 2
The electrical resistance (R2) can also be heated if the low-impedance electrical series resistor (R9) is switched on
Data Source
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AI summary
The sensor has three temperature-sensitive electrical resistors (R1-R3) connected in parallel in a flow path, where the resistors have negative or positive gradients. Electrical series resistors (R6-R9) are connected in series to each of the electrical resistors. A middle electrical resistor (R2) is mutually connected with the two series resistors (R6, R9) by a switching device (5), where the pre-resistor (R6) is of high impedance and the other pre-resistor (R9) is of low impedance. Detecting devices are provided for the detection of the voltage drops in the pre-resistors. Independent claims are also included for the following: (1) a method for testing the function of a flow sensor (2) a method for operating a flow sensor.