Pulsed Flow Sensor Circuit for Aerosol Puff Detection
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Solution Overview
Problem
Existing flow sensor systems for aerosol generating systems, such as smoking systems, face challenges in efficiently detecting fluid flow indicative of puffs while minimizing power consumption and maintaining sensitivity, especially in varying environmental conditions and user habits.
Innovation Solution
A flow sensor system utilizing a sensing circuit with a sensing resistor and a pulsed driving signal, where the sensing circuit is powered only when the pulsed driving signal is high, and frequency is adjusted between two modes to balance sensitivity and power consumption, incorporating a current source for constant current operation and a differential amplifier for voltage output amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensing circuit is continuously powered to maintain high sensitivity for detecting fluid flow, then the sensitivity is improved, but the power consumption increases
Solution Approach 1:
The sensing circuit is powered periodically using a pulsed driving signal instead of continuous power supply. The circuit operates in alternating active and standby states, where the pulsed signal activates the sensing circuit only during measurement periods. This periodic operation maintains the ability to detect fluid flow while significantly reducing average power consumption compared to continuous operation.
2Speed
If the pulsed driving signal frequency is increased to improve response time for detecting puffs, then the response speed is improved, but the power consumption increases
Solution Approach 1:
The system dynamically adjusts the frequency of the pulsed driving signal based on operational requirements. During normal operation, a lower frequency is used to minimize power consumption. When a puff is detected or anticipated, the frequency is increased to improve response time. This dynamic frequency adjustment allows the system to optimize between power consumption and response speed according to real-time conditions.
3Measurement precision
If the sensing circuit operates in high-frequency mode continuously to capture all puff characteristics, then the measurement accuracy is improved, but the battery life decreases
Solution Approach 1:
The sensing circuit alternates between low-frequency and high-frequency operation modes. During extended periods without detected puffs, the circuit operates at low frequency to conserve battery power. When puff activity is detected, the system switches to high-frequency mode to accurately capture puff characteristics. This periodic mode switching ensures that high measurement precision is achieved only when necessary, thereby extending battery life while maintaining adequate puff detection capability.
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 achieves high sensitivity in detecting small changes in fluid flow with reduced power consumption, allowing for continuous operation without a separate on/off switch and adaptive frequency adjustments based on user habits, enhancing both qualitative and quantitative puff information capture.
Implementation Method 1
Active sensors are often based on heat loss as a result of the fluid flow. This type of active sensor is often referred to as a thermal anemometer. The sensor comprises a resistor which is heated to a high temperature. When the flow cools the resistor, the consequent decrease in temperature for a given power, or increase in power to maintain a given temperature, indicates the air flow velocity.
Data Source
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AI summary
There is provided a flow sensor system for sensing fluid flow indicative of a puff in an aerosol generating system. The sensor system includes a sensing circuit comprising a sensing resistor and a voltage output. The sensing resistor is arranged to detect fluid flow based on a change in resistance. The sensing circuit is arranged such that the change in resistance of the sensing resistor causes a change in the voltage output. The sensor system also includes a signal generator arranged to supply a pulsed driving signal to the sensing circuit for powering the sensing circuit. The sensing circuit is powered when the pulsed driving signal is high and not powered when the pulsed driving signal is low. The sensor system is arranged to operate in a first mode, in which no puff is expected or detected and in which the pulsed driving signal has a first frequency, and a second mode, in which a puff is expected or detected and in which the pulsed driving signal has a second frequency, greater than the first frequency.