Converter Pulse Width Shaping Circuit for Vortex Flow Meter Noise
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Solution Overview
Problem
Vortex flow meters face erroneous metering due to noise signals from piping vibrations and electrical noise, especially when the cutoff valve is closed, leading to pulsation in compressible fluids, which are misinterpreted as flow rate signals, and existing solutions like filters and trigger level adjustments are inadequate.
Innovation Solution
A converter pulse width shaping circuit is introduced between the waveform shaping apparatus and the erroneous output preventing apparatus, converting high-frequency pulse signals to low-frequency signals, thereby providing both low-cut and high-cut functions to prevent erroneous metering by shaping the pulse width of input signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a filter is arranged between the flow rate detecting portion and signal generator to enhance the S/N ratio, then the signal quality is improved, but the flow rate range allowing measurement is restricted
Solution Approach 1:
The patent changes the parameter of trigger level dynamically based on the measured flow rate. When flow rate is low, a higher trigger level is applied to suppress noise, and when flow rate is high, a lower trigger level allows measurement. This resolves the contradiction by adapting the trigger level parameter to different operating conditions, maintaining both signal quality and flow rate range.
2Reliability
If the trigger level is expanded to suppress noise signals, then erroneous metering is prevented, but the flow rate range allowing measurement is restricted
Solution Approach 1:
The patent makes the trigger level dynamic rather than fixed. The trigger level changes according to the measured flow rate, being higher when flow is low (to prevent erroneous metering) and lower when flow is high (to maintain measurement capability). This dynamic adjustment resolves the contradiction between reliability and adaptability.
3Productivity
If the cutoff valve is closed to stop fluid flow, then flow rate measurement is halted, but pulsation in compressible fluid causes erroneous signals to be generated
Solution Approach 1:
The patent uses feedback by continuously monitoring the signal frequency and comparing it with the natural frequency of the detection sensor. When pulsation occurs (signal frequency matches natural frequency), the system detects this condition and prevents erroneous metering by adjusting the trigger level or blocking erroneous pulses. This feedback mechanism resolves the contradiction by detecting and correcting erroneous signals in real-time.
4Reliability
If existing erroneous metering preventing devices are used, then some noise suppression is achieved, but high-frequency noise signals from piping vibration are not effectively filtered
Solution Approach 1:
The patent introduces frequency discrimination as an additional parameter for noise suppression. By analyzing the frequency of incoming signals and comparing with the natural frequency of the detection sensor, the system can identify and filter high-frequency noise from piping vibrations while maintaining sensitivity to valid flow rate signals. This resolves the contradiction by adding frequency-based filtering 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
This solution effectively reduces erroneous metering by converting high-frequency noise signals into low-frequency signals that can be cut off, enhancing the accuracy of flow rate measurements and preventing over-triggering, while being versatile enough for retrofitting existing vortex flow meters.
Implementation Method 1
combines, when high frequency pulse signals of a frequency not lower than a predetermined value are successively input, those high frequency pulse signals to convert them to a low frequency pulse signal
Data Source
AI summary
A converter pulse width shaping circuit (6) according to the present invention is provided between a waveform shaping apparatus (4) and an erroneous output preventing apparatus (5) that are provided between a flow rate detecting portion (1) and a flow rate metering mechanism (3). When high frequency pulse signals of a frequency not lower than a predetermined value are successively input, the converter pulse width shaping circuit (6) combines those high frequency pulse signals to convert them to a low frequency pulse signal, which is then output to the erroneous output preventing apparatus (5) having a low-cut function. In the present invention, a vortex flow meter is made up of a converter (2) including the converter pulse width shaping circuit (6) described above.