Liquid Level Sensor Intermittent Voltage Control
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Solution Overview
Problem
Conventional liquid level detection devices fail to accurately detect liquid levels over a long period when exposed to electrolytic liquids like bio-ethanol due to electrochemical reactions causing contact resistance increases, with insufficient countermeasures for conducting time in existing technologies.
Innovation Solution
A liquid level detection device with a sensor having variable resistance and a power supply circuit that applies voltage intermittently, with a conducting time of 40 ms or less per cycle, and a ratio of 50% or less, using first and second conductive patterns with a capacitor formed between them to suppress electrochemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage is continuously applied to the sensor, then liquid level detection can be performed continuously, but electrochemical reactions cause contact resistance increase and measurement interruption
Solution Approach 1:
The power supply circuit applies voltage to the sensor intermittently in predetermined cycles with a conducting time of 40 ms or less per cycle. This periodic voltage application allows liquid level detection while suppressing electrochemical reactions at the sliding contact surfaces, preventing contact resistance increase and measurement interruption.
2Object-affected harmful factors
If voltage is applied intermittently to suppress electrochemical reactions, then contact resistance is maintained, but detection accuracy and response time may be affected
Solution Approach 1:
The conducting time parameter is optimized to 40 ms or less per cycle, which is sufficient to obtain accurate liquid level detection signals while being short enough to suppress electrochemical reactions. This parameter optimization maintains both measurement precision and low contact resistance.
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 effectively suppresses electrochemical reactions, allowing for accurate and prolonged liquid level detection even in electrolytic liquids by controlling the energy exposure and ion movement, maintaining low contact resistance and preventing corrosion.
Implementation Method 1
when the sliding contact surfaces of the resistor and the contact element 114 of the sensor 102 are exposed to the electrolytic liquid, an electrochemical reaction such as electrolytic corrosion is produced on the sliding contact surfaces as the voltage is applied thereto
Implementation Method 2
The sensor 102 has a variable resistance 103 which changes a resistance value by allowing a contact to move in association with a change in liquid level to thereby output a voltage signal according to a resistance value
Data Source
AI summary
A liquid level detection device includes a sensor provided in a container which stores a liquid therein and having a variable resistance which changes a resistance value in association with a change of liquid level to output a voltage signal according to the resistance value of the variable resistance when a voltage is applied thereto, and a power supply circuit applying the voltage to the sensor intermittently on a predetermined cycle. A conducting time during which the power supply circuit applies the voltage to the sensor is equal to or less than 40 ms per cycle.