Variable Frequency Charge Pump for Capacitive Level Sensor
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Solution Overview
Problem
Existing capacitive level sensors face limitations in measuring fluids with varying dielectric constants, as they operate effectively only within a predetermined capacitance range, leading to functionality issues with high dielectric fluids and resolution problems with low dielectric fluids, and are not adaptable to different dielectrics.
Innovation Solution
The capacitive level sensor adjusts its charging frequency based on the dielectric constant of the fluid, allowing for a wider range of measurement by slowing down frequency for high dielectric fluids and increasing frequency for low dielectric fluids, thereby optimizing the capacitive range and improving resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed frequency charge pump circuit is used, then the circuit operates correctly within a predetermined capacitance range, but the sensor cannot measure fluids with high dielectric constants or achieve high resolution with low dielectric constant fluids
Solution Approach 1:
The charge pump frequency is made variable rather than fixed. The system dynamically adjusts the charge pump frequency based on the measured capacitance value, allowing optimal measurement resolution across different dielectric constant ranges. When high capacitance is detected (high dielectric constant), the frequency is reduced; when low capacitance is detected (low dielectric constant), the frequency is increased to maximize resolution.
Solution Approach 2:
The system changes the operating frequency parameter of the charge pump circuit based on the dielectric constant of the fluid being measured. By monitoring the capacitance and adjusting the frequency parameter accordingly, the system maintains optimal measurement resolution across a wide range of dielectric constants, from low to high.
2Measurement precision
If the charge pump operates at a fixed frequency, then the circuit is simple to implement, but it cannot provide both high resolution for low dielectric fluids and increased range for high dielectric fluids
Solution Approach 1:
The system uses feedback from the measured capacitance value to control the charge pump frequency. The measured capacitance (which reflects the dielectric constant) is used to adjust the frequency in real-time, creating a closed-loop system that automatically optimizes resolution without requiring complex external control circuitry.
Solution Approach 2:
The charge pump circuit adjusts its own operating frequency based on the measurement conditions. The system essentially self-regulates by using the measured capacitance information to control its charging rate, eliminating the need for complex external frequency control mechanisms.
3Reliability
If reference electrodes are protected from corrosive fluids using circuit boards with varying dielectrics, then the electrodes are protected from corrosion, but non-linear effects are introduced that limit accurate measurement across different dielectric constants
Solution Approach 1:
The system compensates for the non-linear effects introduced by the protective circuit board by dynamically changing the charge pump frequency. The frequency adjustment counteracts the non-linear capacitance variations caused by the varying dielectric layers in the circuit board, allowing accurate measurements across different fluid dielectric constants despite the protective barrier.
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
This approach enables the sensor to accurately measure fluid levels across a wide range of dielectric constants, providing high resolution for low dielectric fluids and increased range for high dielectric fluids, while reducing non-linear effects from protective circuit boards.
Implementation Method 1
A capacitive sensor, which includes one or more conductive plates, is sensitive to changes in the dielectric constant of material or fluid near or surrounding the plates. The capacitive sensor detects the presence or lack of material in the vicinity of the plates by measuring the capacitance between the plates.
Implementation Method 2
A capacitive sensor, which includes one or more conductive plates, is sensitive to changes in the dielectric constant of material or fluid near or surrounding the plates.
Implementation Method 3
the charge pump circuit of the Livingston patents operates correctly as long as operation occurs within a predetermined capacitance range
Data Source
AI summary
A method of determining a fluid or material level. The method comprises the steps of : providing, at a first frequency, a current operatively capable of changing a capacitor; charging at least first and second capacitive devices to a predetermined voltage using the provided current; measuring the amount of current respectively necessary to charge the first and second capacitive devices to the predetermined voltage; determining a liquid level based on the measured signals from charging the first and second capacitive devices; and varying the first frequency.