Photoelectric Flowmeter Circuit With DC Blocking for Stable Signal Levels
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Solution Overview
Problem
Existing photoelectric flowmeters face issues with signal invalidation due to increased signal troughs caused by scale adhesion and gradual decrease in light-emitting intensity, leading to incorrect voltage level detection by the micro control unit.
Innovation Solution
Incorporation of a direct current (DC) blocking circuit, specifically a high pass filter circuit and clamp diode, to eliminate DC bias voltage and ensure accurate voltage level detection even with scale adhesion or decreased light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pull-up resistor is used in the photoelectric flowmeter circuit, then the circuit can maintain a high voltage level when light is blocked, but the signal trough increases when scale adhesion or light intensity decrease occurs, causing incorrect voltage level detection
Solution Approach 1:
The patent extracts and removes the DC bias voltage component from the signal path by introducing a DC blocking circuit (capacitor C1) between the photoelectric conversion circuit and the output. This separates the AC signal component (which contains the flow measurement information) from the DC bias component, allowing the signal trough to return to near-zero voltage levels even when scale adhesion or light intensity changes occur, thereby resolving the voltage level detection accuracy issue
Solution Approach 2:
The patent changes the electrical parameters of the circuit by introducing a capacitor C1 with specific capacitance value (100nF-10uF) to block DC while passing AC signals. This parameter change transforms the circuit's voltage characteristics, enabling the output voltage to swing around 0V instead of being biased at a high level, thus improving both reliability and measurement precision
2Duration of action of stationary object
If the light-emitting diode operates for a long time, then the flowmeter can continuously measure flow, but the light-emitting intensity gradually decreases, causing the signal trough to increase and become invalid
Solution Approach 1:
The patent implements a feedback mechanism where the DC blocking circuit continuously adapts to changes in light intensity by blocking the DC bias voltage. This allows the circuit to maintain proper signal levels regardless of the LED's aging state, ensuring long-term reliability without requiring manual recalibration or replacement
Solution Approach 2:
The patent provides beforehand cushioning against the inevitable degradation of the LED by pre-installing the DC blocking circuit. This circuit component proactively compensates for future light intensity decreases, cushioning the system against the harmful effects of component aging and maintaining signal validity throughout the extended service life
3Adaptability or versatility
If scale adhesion occurs on the light-transmitting part, then the flowmeter can still operate, but the received light intensity decreases, causing the signal trough to increase and exceed the low voltage level threshold
Solution Approach 1:
The patent extracts the DC bias voltage that causes the signal trough elevation due to scale adhesion. By removing this DC component through the blocking capacitor, the signal can swing freely around 0V, allowing the system to tolerate significant scale adhesion while maintaining accurate voltage level detection at the standard thresholds
Solution Approach 2:
Instead of trying to prevent scale adhesion or amplify the weak signal past the threshold, the patent inverts the approach by blocking the DC bias and allowing the AC signal to swing below the low voltage threshold. This inversion of the detection strategy enables the system to accommodate scale adhesion while maintaining measurement precision
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
The DC blocking circuit enables the output of standard level signals, enhancing the flowmeter's ability to withstand scale attachment and extending its service life by preventing incorrect voltage level detection.
Implementation Method 1
An existing photoelectric flowmeter emits light by a light-emitting diode and receives light by a photosensitive triode
Implementation Method 2
the collector of the photosensitive triode is electrically connected to a circuit output end through a direct current (DC) blocking circuit
Data Source
AI summary
A photoelectric flowmeter circuit includes a circuit power supply end. The photoelectric flowmeter circuit also includes a light-emitting element, including a first end electrically connected to the circuit power supply end and a second end electrically connected to ground. The photoelectric flowmeter circuit also includes a photosensitive triode, including a collector electrically connected to the circuit power supply end and an emitter electrically connected to the ground. The photoelectric flowmeter circuit also includes a direct current (DC) blocking circuit. The photoelectric flowmeter circuit also includes a circuit output end electrically connected to the collector of the photosensitive triode through the DC blocking circuit.