A liquid filter
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Solution Overview
Problem
Condensate tray systems in refrigeration and air conditioning units face challenges in accurately detecting liquid levels due to surface tension and contamination, leading to incomplete drainage and potential microbial growth, with existing sensors unreliable near the bottom and inefficient pumping causing residual liquid and noise issues.
Innovation Solution
A filter with integrated capacitive sensors on a printed circuit board (PCB) that measures liquid depth and rate of change on both sides, allowing for accurate determination of when to stop pumping and preventing clogging, combined with anti-microbial properties and self-priming pumps to ensure complete drainage without noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional level sensors are used near the bottom of the tray, then liquid level detection is attempted, but the sensors become unreliable due to surface tension and contamination effects
Solution Approach 1:
The patent replaces traditional mechanical contact-based level sensors with capacitive sensing technology. The capacitive sensor detects liquid level through electrical field interaction without physical contact, eliminating surface tension and contamination issues that plague mechanical sensors. The sensor measures changes in capacitance caused by the dielectric properties of liquid versus air, providing reliable detection even near the bottom of the tray.
Solution Approach 2:
The capacitive sensor acts as an intermediary between the control system and the liquid level. Instead of direct mechanical contact, the sensor uses electrical field interaction mediated through the dielectric medium (liquid or air) to detect level changes. This intermediary approach allows accurate measurement without the sensor elements being directly exposed to contamination or surface tension effects.
2Quantity of substance
If the pump continues to run after the low level sensor is reached, then more liquid can be removed from the tray, but the pump generates unpleasant noise and may run dry
Solution Approach 1:
The capacitive sensor provides continuous feedback on liquid level and pumping rate to the control system. By monitoring the rate of change of liquid level, the system can detect when the tray is nearly empty and adjust pump operation accordingly. This feedback mechanism allows the pump to continue running briefly after traditional sensors trigger shutdown to remove residual liquid, while stopping before dry running conditions cause noise or damage.
Solution Approach 2:
The system dynamically adjusts pump operation based on real-time capacitive sensor readings. Instead of fixed threshold-based control, the pump runtime is continuously optimized based on the measured liquid level and its rate of change. This dynamic control allows flexible adjustment of pump operation to maximize liquid removal while avoiding dry running conditions.
3Area of stationary object
If the tray is designed with wide, shallow configuration to catch condensate, then coverage area is increased, but a significant amount of liquid remains in the tray once the low level is reached
Solution Approach 1:
The patent replaces traditional mechanical level sensors with capacitive sensing to enable more precise detection of residual liquid levels in the wide, shallow tray. The capacitive sensor's ability to detect small changes in dielectric constant allows it to accurately measure the thin layer of residual liquid that remains after pumping, enabling the system to optimize pump runtime to remove this residual liquid without causing dry running.
4Object-affected harmful factors
If residual liquid remains in the tray after pumping, then hygiene hazards arise due to microbial growth, but extending pump runtime to remove all liquid may cause noise and energy waste
Solution Approach 1:
The capacitive sensor provides continuous feedback on liquid level and pumping effectiveness to the control system. By monitoring the rate of change of liquid level, the system can determine when residual liquid has been sufficiently removed to minimize microbial growth risk, and when further pumping would only remove negligible amounts of liquid while consuming additional energy and creating noise.
Solution Approach 2:
The system changes the control parameter from fixed time-based or threshold-based pump operation to rate-of-change-based control. By monitoring how quickly the liquid level is dropping, the system can optimize pump runtime to remove liquid that poses hygiene risks while stopping before removing liquid that would provide no hygiene benefit but would consume energy and create 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 solution enables precise liquid level detection and efficient drainage, reducing residual liquid and microbial growth risks, while providing diagnostic information on filter blockages and pump efficiency, ensuring complete emptying without noise.
Implementation Method 1
Capacitive sensors can readily be integrated into the PCB as it is simply a matter of forming a number of conductive tracks on the PCB. Capacitive sensors also undergo a continuous change of capacitance as the liquid level falls so can provide an accurate measurement as well as information on the rate of change of depth.
Data Source
AI summary
A liquid filter, for example for a condensate reservoir (1), formed of a printed circuit board (8) comprising a plurality of holes (9) forming a filter screen through the printed circuit board. A first set of capacitive elements (16, 17) are formed in the printed circuit board (8) forming a first capacitive sensor (12) capable of measuring the depth of the liquid adjacent to the filter. The capacitive elements (16,17) may be shielded (19) on one side such that they measure the depth on one side of the filter. A second set of capacitive elements (16′, 17′) may be provided to measure the depth of the liquid on the opposite side of the filter.