Flow Measuring Device Edge Relief Circuit Noise Reduction
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Solution Overview
Problem
Existing flow measuring devices output signals with steep rising and falling edges, which can act as noise sources and affect surrounding apparatus, despite attempts to mitigate this with delay circuits.
Innovation Solution
Incorporating an edge relief part that gradually changes the control voltage over time to smooth the signal edges, using a pattern instruction part and control voltage output unit to define and apply this change, thereby reducing signal steepness and noise potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a switching element is used to output a rectangle wave signal with steep edges, then the signal clarity and definition are improved, but the signal becomes a noise source that affects surrounding apparatus
Solution Approach 1:
The patent segments the single switching element into multiple switching elements (first switching element and second switching element) that operate in sequence. The edge relief part controls these switching elements to turn on/off at different times, dividing the single steep edge transition into multiple smaller steps, thereby reducing the overall noise impact while maintaining signal definition.
Solution Approach 2:
The patent introduces dynamic control through the edge relief part that adjusts the timing and sequence of switching element operations. By dynamically controlling when each switching element turns on or off based on the flow signal pattern, the system creates a stepped transition that reduces noise while preserving signal integrity.
2Object-generated harmful factors
If a delay circuit with parallel switching and capacity elements is used to soften edges, then some noise is reduced, but the rising and falling edges remain steep and noise still occurs
Solution Approach 1:
Instead of using a single capacity element with one switching element, the patent segments the switching function into multiple switching elements controlled in sequence. This segmentation allows for a more gradual, stepped transition that effectively softens the edges without compromising signal definition, going beyond what a single parallel RC circuit can achieve.
Solution Approach 2:
The edge relief part acts as an intermediary control unit that manages the sequential operation of multiple switching elements. This intermediary layer provides fine-grained control over the edge transition process, enabling a stepped approximation of the ideal signal shape that reduces noise while maintaining precision.
3Object-generated harmful factors
If multiple switching elements are controlled sequentially to create stepped edges, then noise is significantly reduced, but the device complexity increases
Solution Approach 1:
The edge relief part serves multiple functions: it controls the sequential operation of multiple switching elements, generates the appropriate timing signals, and adapts to different flow signal patterns. By consolidating these control functions into a single multi-functional unit, the patent reduces the overall system complexity despite using multiple switching elements.
Solution Approach 2:
The patent changes the temporal parameters of the switching elements' operation rather than adding complex hardware. By adjusting the timing and sequence of switching element activation based on flow signal characteristics, the system achieves noise reduction through parameter optimization rather than structural complexity.
Data Source
AI summary
A flow measuring device includes an output portion that outputs an electric signal having a shape of rectangle wave with an edge rising or falling in a signal value. The electric signal corresponds to a flow rate of intake air drawn into an internal-combustion engine. The output portion applies or stops a control voltage to a switching element disposed in an output wiring through which the electric signal is output so as to form the edge. The output portion has an edge relief part that changes the control voltage with progress of time so as to gradually increase or decrease the signal value at the edge.