Capacitive Sensor for Liquid Water Content Detection
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Solution Overview
Problem
Existing capacitive sensors for detecting liquid properties, particularly water content in oil, face challenges in achieving accurate and reliable measurements due to limitations in sensitivity and interference, especially when dealing with small amounts of water impurities.
Innovation Solution
A sensor device employing a capacitive measuring principle with a capacitor arrangement and an evaluation circuit that uses an AC voltage source and measuring resistor to form a low-pass filter, allowing for accurate detection of liquid properties by measuring capacitance values, which are dependent on the dielectric properties of the liquid, enabling the recognition of small water content in oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive sensors are used for detecting water content in oil, then the device structure is simple, but the measurement precision and sensitivity are insufficient for detecting small amounts of water impurities
Solution Approach 1:
The sensor is divided into multiple independent capacitor elements arranged in series between two electrodes. Each capacitor element contributes to the total capacitance measurement, and the series arrangement allows the sensor to detect small changes in dielectric properties caused by water impurities while maintaining a relatively simple overall structure.
Solution Approach 2:
The invention changes the electrical parameters of the sensing system by using multiple capacitors in series rather than a single capacitor. This configuration amplifies the effect of small dielectric changes caused by water impurities, improving measurement precision without requiring complex external circuitry.
2Reliability
If conventional capacitive measurement methods are used, then the device is simple, but interference and noise reduce reliability of measurements
Solution Approach 1:
Multiple capacitor elements are merged in series between the two electrodes, creating a unified sensing system where the combined capacitance measurement is more reliable than individual measurements. This merging of measurement paths reduces the impact of noise and interference on the final result.
Solution Approach 2:
The evaluation circuit processes the impedance signal from the capacitor array and provides feedback control to maintain stable measurements. The system continuously monitors the capacitance changes and adjusts measurement parameters to compensate for interference and noise, improving reliability.
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 highly accurate detection of water content in oil with simple means, ensuring reliable measurement of even small amounts of water, reducing interference and improving sensitivity by utilizing a capacitive measuring principle and appropriate excitation frequencies.
Implementation Method 1
A sensor device employing a capacitive measuring principle with a capacitor arrangement and an evaluation circuit that uses an AC voltage source and measuring resistor to form a low-pass filter, allowing for accurate detection of liquid properties by measuring capacitance values
Implementation Method 2
measuring capacitance values, which are dependent on the dielectric properties of the liquid, enabling the recognition of small water content in oil
Data Source
AI summary
Aspects of the present disclosure relate to a sensor device and a method for detecting properties of a liquid. In one example, the liquid is accommodated in an inner chamber. A capacitor arrangement in the inner chamber has spaced, opposing capacitor surfaces so that at least part of the liquid accommodated in the inner chamber is arranged between the capacitor surfaces. An evaluation device for supplying an output signal A depending on a capacitance value of the capacitor arrangement includes an excitation circuit and an evaluation circuit. The excitation circuit has at least one measuring resistor and an AC voltage source configured to apply an AC voltage to a series circuit including the measurement resistor and the capacitor arrangement. The evaluation circuit has an output supplying the output signal A by measuring a voltage across the capacitor arrangement.