Aerosol Particle Mass Sensor with Dynamic Cycle Control
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Solution Overview
Problem
Existing mass sensors for aerosol particle measurement have unpredictable lifetimes due to varying mass deposition rates, making it difficult to estimate when the sensor needs replacement or maintenance, especially in environments with high pollutant concentrations.
Innovation Solution
A mass sensor with a controller that adjusts the sensing cycle duration based on a pre-set mass change, ensuring a constant lifetime by limiting particle deposition to each sensing cycle, and using a resonant mass sensor for accurate mass measurement, which can be implemented in consumer devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fixed duration sensing cycles are used, then measurement frequency is maintained, but sensor lifetime becomes unpredictable due to varying mass deposition rates
Solution Approach 1:
The sensing cycle duration is made dynamic rather than fixed. The controller automatically adjusts the sensing cycle length based on the actual mass deposition rate, extending the cycle when deposition is slow and shortening it when deposition is fast, thereby maintaining reliable lifetime prediction across varying environmental conditions
Solution Approach 2:
The system implements feedback control by continuously monitoring the mass change on the sensor element during sensing cycles. This feedback information is used by the controller to adjust subsequent sensing cycle durations, ensuring that the sensor operates within reliable parameters regardless of environmental variations
2Measurement precision
If longer sensing cycles are used to improve measurement accuracy in low concentration environments, then measurement precision improves, but mass accumulation increases reducing sensor lifetime
Solution Approach 1:
The sensing cycle duration dynamically adapts to environmental conditions. In low concentration environments, the cycle extends to accumulate sufficient mass for accurate measurement, while in high concentration environments, the cycle shortens to prevent excessive mass accumulation, thereby balancing measurement precision with sensor lifetime preservation
Solution Approach 2:
The system changes the operational parameter (sensing cycle duration) based on detected mass deposition rates. By adjusting this parameter in response to environmental conditions, the system optimizes both measurement precision and sensor longevity without requiring manual intervention
3Measurement precision
If sensing cycle duration is extended for low pollutant concentrations, then measurement accuracy improves, but in high concentration environments excessive mass deposition occurs
Solution Approach 1:
The controller uses real-time feedback from the detector to monitor mass accumulation rate and adjusts sensing cycle duration accordingly. This feedback mechanism prevents excessive mass deposition in high concentration environments while ensuring sufficient accumulation for accurate measurement in low concentration environments
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 approach allows for a predictable sensor lifetime, reduced mass change in each sensing cycle, and accurate measurement of particle mass concentration, even in high pollutant environments, making it suitable for consumer applications.
Implementation Method 1
use of a micromachined silicon cantilever device with a picogram level of mass resolution... MEMS based resonant particle measurement device
Data Source
AI summary
A mass sensor is provided for measuring a particle mass within an aerosol. The duration of a sensing cycle is set such that a pre-set change in mass resulting from particles deposited is caused. In the absence of cleaning, the lifetime of the sensor is dependent on the total mass deposited. As a result, the lifetime is made essentially constant by this approach, because each sensing operation is made to give rise to a constant amount of deposited particle mass. This means the lifetime can be predicted more accurately.