Thermistor Flow Sensor Circuit With Multi-Temperature Modes
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Solution Overview
Problem
Existing flow rate sensing systems in breathing assistance apparatuses face challenges in accurately measuring gas flow rates across a wide range of temperatures due to variations in temperature differences between the gas flow and the thermistor target temperature, leading to inaccurate readings and potential distortions.
Innovation Solution
A thermistor circuit configured to operate in multiple target temperature modes, allowing it to adjust its resistance values by connecting or bypassing resistors, thereby maintaining accurate flow rate measurements across varying gas flow temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single target temperature is used for the thermistor, then the device complexity is reduced, but the measurement precision deteriorates because accurate flow rate measurement across varying ambient temperatures cannot be achieved
Solution Approach 1:
The patent implements dynamic target temperature adjustment by switching between multiple target temperature modes (first target temperature mode and second target temperature mode) based on the measured ambient temperature. The controller dynamically selects which target temperature to maintain for the thermistor, allowing the system to adapt to varying environmental conditions and maintain measurement accuracy across different operating temperatures.
Solution Approach 2:
The patent changes the target temperature parameter of the thermistor based on the measured temperature of the ambient air. When the ambient temperature exceeds a threshold, the system switches from a first target temperature to a second target temperature, thereby adjusting the operating parameters to compensate for temperature-induced measurement errors and maintain flow rate measurement precision.
2Measurement precision
If the thermistor target temperature is changed based on ambient temperature, then the measurement precision is improved, but the use of energy increases due to additional heating or cooling requirements
Solution Approach 1:
The patent changes the target temperature parameter of the thermistor based on the measured temperature of the ambient air. When the ambient temperature exceeds a threshold, the system switches from a first target temperature to a second target temperature, thereby adjusting the operating parameters to compensate for temperature-induced measurement errors and maintain flow rate measurement precision.
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
The system provides precise flow rate measurements by ensuring the gas flow temperature remains within a manageable range relative to the thermistor's target temperatures, enhancing accuracy and reducing distortions.
Implementation Method 1
a voltage divider containing a thermistor. The gases flow rate may be determined based upon a voltage output indicating an amount of power needed to maintain the thermistor at a target temperature
Implementation Method 2
a voltage divider containing a thermistor. The gases flow rate may be determined based upon a voltage output indicating an amount of power needed to maintain the thermistor at a target temperature
Data Source
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AI summary
A gases flow rate sensing system may be configured to operate in at least two different target temperature modes, based upon a measured temperature of the gases flow. In some embodiments, the gases flow sensing system may have a voltage divider containing a thermistor. The gases flow rate may be determined based upon a voltage output indicating an amount of power needed to maintain the thermistor at a target temperature as specified by the target temperature mode, and a measured temperature of the gases flow.