Resistivity Measuring Circuit Square Wave AC Voltage
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Solution Overview
Problem
Existing resistivity-measuring apparatuses face challenges in accurately measuring the resistivity of oils due to high resistivity values, which leads to small current flow and instability in AC voltage responsiveness, and applying high voltage can cause oil deterioration.
Innovation Solution
A resistivity-measuring circuit using square wave AC voltage with an amplitude of 1 V to 42 V and a frequency of 0.5 Hz to 30 Hz, combined with a double-sided support structure for the liquid sample measuring cell to stabilize signal output and prevent electrode shift, and a temperature control system to maintain constant liquid sample temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high voltage is applied to increase detected current, then measurement sensitivity is improved, but the liquid sample deteriorates due to oxidation
Solution Approach 1:
The patent changes the voltage parameter from high voltage (1000V) to low voltage (1V to 42V) range, and adjusts the frequency parameter to 0.5Hz to 30Hz square wave AC voltage. This parameter change allows sufficient current detection while preventing liquid sample oxidation and deterioration.
2Speed
If AC voltage of 100 Hz is applied, then measurement speed is improved, but signal stabilization fails due to floating capacitance
Solution Approach 1:
The patent changes the frequency parameter from 100Hz to a lower range of 0.5Hz to 30Hz, and uses square wave AC voltage instead of sinusoidal voltage. This parameter change allows the signal to stabilize before polarity switching occurs, improving measurement reliability while maintaining adequate measurement speed.
3Quantity of substance
If DC voltage is applied, then current flow is increased, but electric double layer formation causes measurement instability
Solution Approach 1:
The patent applies periodic square wave AC voltage instead of DC voltage. The periodic reversal of voltage polarity prevents electric double layer formation at the electrode-liquid sample interface, maintaining stable measurement conditions while sufficient current flows through the high-resistivity liquid sample.
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 continuous, accurate measurement of resistivity while preventing oil deterioration, improving measurement accuracy and reducing errors associated with temperature variations.
Implementation Method 1
measures the resistivity of the liquid sample between a pair of electrodes by detecting voltage generated between the pair of electrodes
Implementation Method 2
the formation of electric double layers at the boundaries between the electrodes and the liquid sample can be suppressed to continuously measure the resistivity of the liquid sample
Data Source
AI summary
The present invention is one that makes it possible to continuously measure the resistivity of a liquid sample with accuracy as well as preventing the deterioration of the liquid sample associated with measurement, such as change in quality, and relates to a resistivity-measuring circuit C that measures the resistivity in order to sense the deterioration of the liquid sample. The resistivity-measuring circuit C is one that calculates the resistivity of the liquid sample by detecting voltage generated between an outer electrode and an inner electrode, and between the outer electrode and the inner electrode, applies square wave AC voltage having an amplitude of 1 V to 42 V and a frequency of 0.5 Hz to 30 Hz.