Thermal Mass Flow Meter Sensor Wire Pulse Signal Control
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Solution Overview
Problem
Thermal type mass flow meters face challenges in balancing heat generation from sensor wires with measurement accuracy, as reducing heat generation can lead to decreased accuracy and increasing it can worsen associated problems like thermal syphoning and fluid deterioration.
Innovation Solution
A method involving the use of pulse signals with varying intensities for heat generation in sensor wires, instead of traditional DC electric voltage, to maintain signal intensity while reducing energy consumption and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC electric voltage is applied to sensor wires to generate heat, then measurement accuracy is maintained, but heat generation causes thermal syphoning and fluid deterioration
Solution Approach 1:
The patent applies periodic pulse signals instead of continuous DC voltage to the sensor wires. The pulse signal has a width of 100 μs or less and repeats at a frequency of 1 kHz or higher, creating periodic heating cycles that allow the system to maintain measurement accuracy while reducing cumulative heat generation and its associated harmful effects like thermal syphoning and fluid deterioration.
Solution Approach 2:
The patent changes the electrical parameters by using high-frequency pulse signals with specific duty cycles instead of continuous DC voltage. This parameter transformation allows the sensor wires to generate sufficient heat for accurate measurement during the pulse duration while the average power input is reduced, thereby minimizing thermal syphoning and fluid deterioration effects.
2Object-generated harmful factors
If heat generation from sensor wires is reduced, then thermal syphoning and fluid deterioration are minimized, but measurement accuracy decreases
Solution Approach 1:
By using periodic pulse signals with high frequency (1 kHz or higher) and short width (100 μs or less), the system achieves effective heat generation during each pulse for accurate measurement while the duty cycle limitation ensures that overall heat generation remains low enough to prevent thermal syphoning and fluid deterioration.
Solution Approach 2:
The patent introduces dynamic pulsing characteristics to the otherwise static heating process. The pulse signal dynamically switches between on and off states, creating time-varying heat generation that optimizes the balance between maintaining measurement accuracy during pulse periods and minimizing harmful thermal effects during off periods.
3Measurement precision
If pulse signal width is increased, then signal intensity is improved, but heat generation increases causing thermal syphoning
Solution Approach 1:
The patent optimizes the pulse signal parameters by setting the pulse width to 100 μs or less and the repetition frequency to 1 kHz or higher. This parameter configuration achieves sufficient signal intensity for accurate measurement while keeping the duty cycle low enough to prevent excessive heat generation and thermal syphoning.
Solution Approach 2:
The high-frequency periodic pulsing allows the system to accumulate sufficient signal intensity over multiple cycles while the brief duration of each pulse and the repetition rate prevent excessive heat buildup that would cause thermal syphoning.
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 reduces heat generation from sensor wires while maintaining measurement accuracy, improving the signal-to-noise ratio and reducing issues like zero-point variation and thermal syphoning, enabling continuous and accurate flow rate monitoring.
Implementation Method 1
when the pair of sensor wires is made to generate heat by applying a predetermined electric voltage (or a predetermined electric current) thereto
Implementation Method 2
heat generated from the sensor wires is removed (drawn) by a fluid which flows through the sensor tube
Implementation Method 3
electrical resistance value of the sensor wire on the upstream side becomes lower than an electrical resistance value of the sensor wire on the downstream side
Data Source
AI summary
By supplying a pulse signal to sensor wires to make the sensor wires generate heat, instead of applying DC electric voltage to the sensor wires, an amount of energy supplied to the sensor wires is decreased while maintaining a signal intensity supplied to the sensor wires, or the signal intensity supplied to the sensor wires is increased while maintaining the amount of energy supplied to the sensor wires. Thereby, a method for measuring a mass flow rate by a thermal type mass flow meter, which can reduce heat generation from the sensor wires while suppressing decrease in measurement accuracy, or can improve measurement accuracy while suppressing increase in heat generation from the sensor wires, is provided.