Acoustic Flow Path Sensing for Accurate Respiratory Gas Measurement
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Solution Overview
Problem
Existing flow path sensing technologies in flow therapy apparatuses face challenges such as transducer delays, temperature drift, dead space, and acoustic noise interference, particularly when using piezoelectric transducers and microphones, which affect accuracy and mounting in compact systems.
Innovation Solution
The use of acoustic sensors, including microphones positioned within or beside the gas flow path, decoupling transmitter and receiver functions, and employing high-pass filters, edge detection, and cross-correlation to mitigate delays and noise, allowing for accurate gas flow characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric transducers are used for flow path sensing, then acoustic signal transmission and reception is enabled, but transducer delays and temperature drift affect measurement accuracy
Solution Approach 1:
The patent extracts the sensing function from the piezoelectric transducer by using a separate microphone to receive acoustic signals. This separation eliminates the transducer delay and temperature drift problems associated with using piezoelectric elements for both transmission and reception, as the microphone is not subject to the same resonant frequency and phase delay issues.
Solution Approach 2:
The patent introduces an intermediary acoustic signal path where the transmitter sends acoustic waves through the gas flow to a separate receiver (microphone). This intermediary approach allows measurement of flow characteristics without the receiver being affected by the transmitter's resonant properties, thereby eliminating transducer delays and improving measurement reliability.
2Measurement precision
If microphones are used to receive acoustic signals, then transducer delays are eliminated, but acoustic noise interference increases
Solution Approach 1:
The patent applies local quality by positioning the microphone in a specific location within the gas flow path where the acoustic signal is strongest and noise is minimized. The receiver is placed at an optimal distance from the transmitter to maximize signal-to-noise ratio, allowing accurate flow measurement while reducing the impact of ambient acoustic noise.
Solution Approach 2:
The system uses feedback by processing the acoustic signal received by the microphone and using it to determine flow rate and other gas characteristics. The controller analyzes the time of flight and signal characteristics, continuously adjusting measurements to compensate for background noise and provide accurate real-time flow data despite the presence of acoustic interference.
3Stability of the object's composition
If transducers are mounted directly in the gas flow path, then temperature equilibration improves measurement stability, but dead space regions affect flow characterization
Solution Approach 1:
The patent transitions from a one-dimensional flow path mounting to a three-dimensional acoustic field approach. By using acoustic waves that propagate through the gas flow in multiple dimensions, the system can measure flow characteristics without the transducers physically obstructing the flow path, thereby eliminating dead space regions while still achieving temperature stability through proper sensor placement and signal processing.
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 configuration enhances measurement accuracy by eliminating transducer delays, temperature drift, and acoustic noise, providing precise determination of gas velocity and concentration without requiring plane waves, suitable for compact systems.
Implementation Method 1
a first acoustic transmitter positioned at a first position in or near a gases flow path, the first acoustic transmitter configured to transmit a first acoustic signal
Implementation Method 2
one or more acoustic receivers positioned between the first position and the second position, the one or more acoustic receivers configured to receive the first and the second transmitted acoustic signals
Implementation Method 3
the hardware processor configured to determine one or more characteristics of the gases flow based on the received first and second acoustic signals
Data Source
AI summary
A respiratory flow therapy apparatus including a sensor module can measure a flow rate of gases or gases concentration provided to a patient. The sensor module can be located after a blower and/or mixer. The sensor module can include at least an ultrasonic transmitter, a receiver, a temperature sensor, a pressure sensor, a humidity sensor and/or a flow rate sensor. The receivers can be immersed in the gases flow path. The receivers can cancel delays in the transmitters and improve accuracy of measurements of characteristics of the gases flow. The receivers can allow for detection of a fault condition in a blower motor of the apparatus.