Capacitive Water Meter Sensor Using Admittance for Conductivity
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Solution Overview
Problem
Existing water meters lack effective means to measure water conductivity for assessing water quality, which is crucial for various applications.
Innovation Solution
Integration of a capacitive electrical conductivity sensor within a water meter, utilizing a capacitor assembly with electrodes embedded in a plastic conduit, to determine water conductivity by measuring complex admittance and mapping it to a model that includes a constant phase element and resistor, allowing for the calculation of conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a water meter is designed to measure flow rate, then flow measurement capability is achieved, but water conductivity measurement capability is lacking
Solution Approach 1:
The water meter is designed to perform multiple functions: traditional flow rate measurement using ultrasonic transducers and additional water conductivity measurement using capacitive sensors (electrodes). This multi-functionality allows a single device to provide both flow quantification and water quality assessment, resolving the contradiction by adding versatility without requiring a completely separate measurement system.
Solution Approach 2:
The capacitive conductivity sensor electrodes are integrated into the existing water meter structure, merging the conductivity measurement function with the flow measurement device. The electrodes are positioned within the meter body, allowing simultaneous or concurrent measurement of both flow rate and conductivity using shared infrastructure and housing.
2Measurement precision
If traditional electrode-based conductivity sensors are used, then conductivity measurement is achieved, but fouling and maintenance issues arise
Solution Approach 1:
The patent replaces traditional direct-contact electrode sensors with a capacitive sensing mechanism. Instead of requiring physical electrical contact between electrodes and water (which causes fouling), the system uses capacitive coupling through the meter housing walls to measure conductivity. This substitution eliminates the fouling problem while maintaining measurement capability through electrical field interaction with the water.
3Adaptability or versatility
If capacitive sensors are integrated into the water meter housing, then conductivity measurement is enabled, but measurement of the sensor signal becomes challenging
Solution Approach 1:
The water meter housing itself serves as an intermediary element in the capacitive sensing system. The housing walls act as one side of the capacitor, with the water serving as the dielectric medium. This intermediary approach allows the sensing electrodes to be positioned inside the housing while measuring conductivity through the housing walls, solving the signal detection challenge by using the existing structure as part of the sensing mechanism.
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
Enables accurate determination of water conductivity, providing insights into water quality parameters such as pollutants and impurities, and facilitating data transmission to utility companies for improved water management.
Implementation Method 1
determining a value of at least part of a complex admittance of a capacitor assembly
Implementation Method 2
calculating the electrical conductivity of the flow of water using inputs comprising the value of at least part of the complex admittance
Data Source
AI summary
A capacitive electrical conductivity sensor is integrated into a water meter. The sensor is used to determine water conductivity, which may be used to determine water quality. A model of a capacitor, a flow of water, and a plastic conduit used to conduct the flow of water passing through a water meter is defined. The model may include a circuit having a constant phase element (CPE) connected to a resistor Rb and a capacitor Cb in parallel. An input signal may be applied to the actual capacitor (not the model) over a range of frequencies. Current flow associated with several frequencies may be used to identify values of Q0 and alpha of the CPE of the model. A value for the resistor Rb is identified using values obtained from measurements. A conductivity of the flow of water may be derived using input values comprising Rb, and the values of Q0 and alpha of the CPE of the model.