Liquid level sensor
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Solution Overview
Problem
Existing condensate pumps in air-conditioning systems face issues with inaccurate liquid level measurement due to manufacturing tolerances, leading to potential overflow or underflow, noise, and reduced pump lifespan, and require time-consuming manual calibration, which is prone to human error and damage.
Innovation Solution
A liquid level sensor system with a microprocessor and multiple sensing elements that dynamically calibrate and control the condensate pump speed based on real-time liquid level data, eliminating the need for manual calibration and providing accurate level monitoring to prevent overflow and ensure proper pump operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance-based liquid level sensors are used to monitor condensate level, then level information can be obtained, but manufacturing tolerances cause measurement inaccuracy leading to potential overflow or underflow
Solution Approach 1:
The patent implements a feedback mechanism where the microprocessor continuously monitors the capacitance sensor output and compares it against dynamically updated reference values stored in non-volatile memory. When the measured level deviates from the reference, the system automatically adjusts pump operation to correct the deviation, ensuring accurate level control despite manufacturing tolerances in the sensor itself.
Solution Approach 2:
The patent changes the operational parameter from fixed threshold control to dynamic reference value control. The microprocessor stores calibrated reference capacitance values in non-volatile memory and uses these as dynamic thresholds for pump control. This allows the system to adapt to individual sensor characteristics while maintaining accurate level control, resolving the measurement precision issue caused by manufacturing tolerances.
2Measurement precision
If manual calibration is performed to account for manufacturing tolerances, then measurement accuracy improves, but the calibration process is time-consuming and prone to human error
Solution Approach 1:
The patent implements self-service calibration where the microprocessor automatically performs the calibration process without human intervention. The system autonomously fills the reservoir, monitors capacitance changes, identifies reference levels (low, mid, high), and stores calibration values in non-volatile memory. This eliminates the time-consuming manual calibration process while maintaining high measurement accuracy.
Solution Approach 2:
The patent performs calibration as a preliminary automatic action during system initialization or first power-up. The microprocessor executes the calibration sequence before normal operation begins, establishing accurate reference values in advance. This preliminary automatic calibration eliminates the need for time-consuming manual calibration during installation or maintenance.
3Productivity
If the condensate pump operates continuously to empty the reservoir, then the reservoir can be emptied sufficiently quickly, but air may be entrained into the pump if the liquid level drops below minimum level
Solution Approach 1:
The patent implements dynamic pump speed control based on real-time liquid level feedback. The microprocessor adjusts the pump motor speed according to the measured liquid level, operating at high speed when liquid is abundant to maximize emptying productivity, and reducing or stopping operation when the level approaches the minimum threshold to prevent air entrainment and maintain pump reliability.
Solution Approach 2:
The patent uses feedback from the capacitance sensor to continuously monitor liquid level and automatically adjust pump operation. The microprocessor receives level information and dynamically controls pump speed to maintain optimal operation, ensuring high productivity when liquid is available while preventing air entrainment when the level drops, thus extending pump lifespan.
4Extent of automation
If a magnetic float system is used to control the pump, then the pump can be operated automatically, but the float can become stuck during prolonged shutdown periods and flow rate control is not possible
Solution Approach 1:
The patent replaces the mechanical magnetic float system with an electronic control system using a capacitance sensor and microprocessor. The capacitance sensor provides contactless level detection that cannot become mechanically stuck, while the microprocessor implements automatic pump control based on electrical signals. This substitution maintains automation while eliminating the reliability issues of mechanical floats during prolonged shutdowns.
Solution Approach 2:
The patent introduces an electrical intermediary (capacitance sensor) between the liquid level and the control system, replacing the direct mechanical coupling of float systems. The capacitance sensor detects liquid level through electrical field changes without physical contact, preventing the sticking problem inherent in mechanical floats while maintaining automatic control functionality.
5Productivity
If the condensate pump is mounted within or adjacent to the AC unit housing, then the travel distance is minimized, but the pump motor vibration causes the pump to rattle and generate undesirable noise
Solution Approach 1:
The patent introduces vibration isolation elements as intermediaries between the pump motor and the housing. These elements (such as rubber mounts or damping materials) absorb and dissipate vibration energy, preventing the transmission of motor vibrations to the housing that would cause rattling and noise, while allowing the pump to remain positioned for efficient condensate transport.
Solution Approach 2:
The patent employs flexible vibration isolation elements (such as rubber mounts or elastomeric dampers) between the pump motor and housing structure. These flexible elements provide mechanical isolation that reduces vibration transmission and noise generation, allowing the pump to be mounted in optimal positions for condensate transport efficiency without creating unwanted noise.
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 ensures reliable and accurate liquid level monitoring, preventing damage and noise issues by dynamically adjusting pump speed and eliminating the need for manual calibration, thereby enhancing the reliability and longevity of the condensate pump.
Implementation Method 1
a sensor module having a first sensing element configured to generate a low liquid level detection signal in response to a liquid reaching the first sensing element
Data Source
Figure 1~2
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Figure 4
AI summary
The present invention provides a liquid level sensor and an automatic calibration process which removes the need for prior manual calibration of the liquid level sensor, as this happens dynamically during installation and use of the pump. Further, by frequently monitoring the calibration of the sensor and correcting for long term drift or contamination on the sensing surface, the reliability of the liquid level sensor is considerably better than those of the prior art. By operating a solid state sensor, there are no moving parts in the liquid level sensor described above.