Drop Detection Device Using Quadrature Demodulation
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Solution Overview
Problem
Existing drop detection systems for metering valves face challenges in accurately detecting small, high-speed droplets due to spatial constraints, low signal amplitudes, and interference from scattered light or external sources, making reliable detection difficult.
Innovation Solution
A drop detection device that generates a carrier signal with a defined pulse frequency and uses quadrature demodulation to analyze modulated measurement signals, determining the presence of a drop based on modulated signal parameters, allowing for precise detection even in cramped spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optoelectronic sensor is positioned close to the valve nozzle to obtain the strongest possible optical signal, then the signal amplitude is improved, but the system complexity increases due to the difficulty of positioning all evaluation electronics directly on the sensor in the limited space
Solution Approach 1:
The detection system is divided into two separate functional modules: a compact optoelectronic sensor unit positioned near the nozzle for signal acquisition, and evaluation electronics located remotely for signal processing. This segmentation allows the sensor to be optimally positioned for signal strength while the complex electronics are placed where space is available, resolving the contradiction between measurement precision and device complexity.
2Reliability
If the distance between the metering valve and the component surface is minimized to enable droplet detection, then the detection capability is improved, but the available space for sensor placement is severely limited
Solution Approach 1:
The evaluation electronics are moved from the constrained three-dimensional space near the nozzle to a remote location, effectively adding a spatial dimension to the system layout. This allows the sensor to remain close to the valve for reliable droplet detection while the electronics are placed in an otherwise unused spatial region, resolving the contradiction between detection capability and available space.
3Speed
If the droplet transit time through the sensor area is reduced due to high droplet velocity, then the detection speed is improved, but the signal amplitude decreases resulting in a low signal-to-noise ratio
Solution Approach 1:
The system uses periodic pulsed illumination synchronized with the droplet ejection cycle. The light source emits periodic light pulses that coincide with the expected droplet passage time, allowing the sensor to accumulate signal photons over multiple synchronized cycles. This periodic action increases the effective signal amplitude and improves the signal-to-noise ratio while maintaining compatibility with high droplet velocities.
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 system enables reliable and fail-safe detection of droplets by distinguishing carrier signal changes caused by drops from noise, improving detection accuracy and robustness against interference.
Implementation Method 1
The light emitted by the light emission unit crosses the trajectory of the droplets to be detected. If a droplet momentarily blocks the light emitted by the light emission unit, this blockage is detected by the light detection unit
Implementation Method 2
Attempting to position an optoelectronic sensor, such as a photodetector, close to the valve nozzle to obtain the strongest possible optical signal, and thus an electrical signal after conversion
Data Source
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AI summary
The invention relates to a drop detection device (11, 11a, 11b) for detecting drops (TR) exiting from a nozzle of a metering valve (DV), preferably a micro-metering valve. The drop detection device (11, 11a, 11b) comprises a signal-generating unit (20), which is designed to generate a carrier signal (TS) having a defined pulse frequency. In addition, the drop detection device (11, 11a, 11b) has a modulation unit (30, 30a), which is designed to generate a modulated signal (MS) that is modulated by a physical interaction between the carrier signal (TS) and a detected drop (TR). Furthermore, the drop detection device (11, 11a, 11b) comprises an evaluation unit (50), which is designed to use the defined pulse frequency to determine, on the basis of the measurement signal (MS), whether a drop (TR) was discharged from the metering valve (DV). The invention further relates to a method (600) for detecting a drop (TR) from a metering valve (DV).