A non-contact liquid level sensor uses the sensing capacitance of water to detect presence of liquid approaching the sensor. The sensor has a specific static capacitance due to the distributed capacitance.
When the liquid level slowly rises close to the inductor, the parasitic capacitance of the liquid is coupled to the static capacitor, causing the final capacitance of the inductor to become more significant. The capacitance signal is then input to the controller IC for signal conversion. The change in capacitance is converted into a proportional variation of the electrical signal, and then the algorithm detects and judges the degree of the change.
When the amount of change exceeds a certain threshold limit the liquid level is considered to reach the sensing point. The same is authenticated in the proposed setup through a buzzer (provision for relay and/or LED interface is possible via mode selection).
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This project will be published in a few weeks. If you want to access it now, refer to Electronics For You’s March 2023 Issue–print or ezine edition.