Flow Sensor Reference Voltage Adaptation for Precision
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Solution Overview
Problem
Existing fluid flow sensors face challenges in maintaining measurement accuracy across varying fluid flow velocities, as the resolution of analog-digital converters is not adequately adapted to the changing dependence of the measured signal on flow velocity.
Innovation Solution
The reference voltage generator adjusts the reference voltage for the analog-digital converter to decrease with increasing fluid flow velocity, enhancing the converter's resolution at higher velocities by using the monitoring signal as a reference, thereby maintaining consistent measurement accuracy across a wider range of flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant reference voltage is used for the analog-digital converter, then the converter operates with fixed resolution, but the measurement precision deteriorates at higher flow velocities due to the weakening dependence of the sensing signal on flow
Solution Approach 1:
The reference voltage is made dynamically adjustable based on the monitoring signal, which varies with flow velocity. The reference voltage generator adapts the reference voltage to match the changing conditions, transforming a static system into a dynamic one that maintains optimal performance across different operating ranges.
Solution Approach 2:
The reference voltage parameter is changed as a function of the monitoring signal to optimize measurement precision. By varying the reference voltage according to flow conditions, the system maintains high resolution and accuracy across the entire measurement range, from low to high flow velocities.
2Measurement precision
If the reference voltage is decreased for higher flow velocities, then the resolution of the converter is increased to maintain measurement precision, but the device complexity increases due to the adaptive reference voltage generator
Solution Approach 1:
The monitoring signal serves multiple functions: it characterizes the flow velocity and simultaneously controls the reference voltage adjustment. This multi-functionality reduces the need for separate sensing and control systems, thereby limiting the increase in device complexity while achieving adaptive resolution.
Solution Approach 2:
The system uses its own monitoring signal to automatically adjust the reference voltage without requiring external intervention or complex control systems. The reference voltage generator is self-regulated by the monitoring signal, enabling the system to adapt to varying conditions using its inherent signals.
3Device complexity
If a fixed reference voltage is used, then the device complexity is minimized, but the linearity of the digitized signal deteriorates across varying flow velocities
Solution Approach 1:
The reference voltage parameter is systematically changed as a function of the monitoring signal to linearize the digitized output. This parameter adjustment compensates for the non-linear relationship between the sensing signal and flow velocity, improving linearity without requiring complex mechanical or structural modifications.
4Reliability
If the reference voltage is adapted to the monitoring signal, then compensation for thermocouple parameter variations is achieved, but the device complexity increases due to the reference voltage generator circuitry
Solution Approach 1:
The monitoring signal provides feedback about the operating conditions and thermocouple performance, which is used to adjust the reference voltage accordingly. This feedback mechanism enables automatic compensation for parameter variations, maintaining reliability while using a relatively simple control approach.
Solution Approach 2:
The reference voltage acts as an intermediary that translates the monitoring signal information into appropriate compensation adjustments. By using the reference voltage as a mediating parameter, the system achieves compensation for thermocouple variations without requiring direct modification of the thermocouple characteristics or complex control algorithms.
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 adjustment improves measurement accuracy and compensates for variations in thermocouple parameters, ensuring a more precise and linearized digitized signal output, even at higher mass flows, while minimizing the impact of membrane stress on the sensor output.
Implementation Method 1
A heater 4 extends over membrane 3... heater 4 is formed by three parallel conductors 4a, 4b, 4c
Implementation Method 2
Two sensing thermopiles 6a and 6b, each consisting of a plurality of thermocouples in series... the difference of the voltages from the thermopiles 6a, 6b... is substantially a measure of the temperature difference ΔT
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The flow sensor comprises a heater (4) arranged between two sensing thermopiles (6a, 6b). In addition, at least one monitoring thermocouple (12a, 12b) is provided for measuring the temperature of the heater (4). The signal from the monitoring thermocouple is used as a reference voltage for an A/D converter, which converts the signals from the sensing thermopiles (6a, 6b). This allows to increase the resolution of the converter at higher flows, which results in more accurate measurements.