Resistance Detection Sensor with Alternating Polarity AC Voltage
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Solution Overview
Problem
Existing resistance detection sensors using AC voltage for liquid resistance measurement suffer from lower detection accuracy and narrower measurement ranges compared to DC voltage methods, while DC voltage application leads to electrolysis and polarization errors.
Innovation Solution
A resistance detection sensor that alternates between applying a DC voltage and an AC voltage of opposite polarity at predetermined intervals, with the AC voltage application period not being an integer multiple of its cycle, to suppress polarization and maintain accurate resistance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a DC voltage is applied between the electrodes to calculate the electrical resistance value of the liquid, then the measurement range and detection accuracy are improved, but electrolysis and polarization occur on the electrode surfaces causing errors
Solution Approach 1:
The patent applies AC voltage periodically between the electrodes at predetermined time intervals during the resistance measurement process. This periodic AC voltage application prevents the accumulation of polarization charge on the electrode surfaces that would otherwise occur with continuous DC voltage application, thereby maintaining measurement accuracy while still allowing DC voltage to be used for the resistance calculation.
Solution Approach 2:
The patent applies AC voltage with opposite polarity to the DC voltage in advance during the measurement process. This preliminary anti-action counteracts the polarization effect before it can significantly degrade the measurement accuracy, by periodically reversing the polarity to prevent charge accumulation on the electrode surfaces.
2Object-generated harmful factors
If an AC voltage is applied between the electrodes to calculate the electrical resistance value of the liquid, then polarization and electrolysis are suppressed, but the detection accuracy and measurement range decrease
Solution Approach 1:
The patent merges the advantages of both DC and AC voltage application methods by using DC voltage as the primary measurement voltage while periodically applying AC voltage to suppress polarization. This combination allows the system to achieve both high measurement accuracy (from DC) and polarization suppression (from AC), resolving the contradiction between the two approaches.
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 effectively suppresses polarization and maintains high detection accuracy for a wider range of electrical resistance values in liquids, thereby improving the reliability of resistance measurements.
Implementation Method 1
the electrical resistance value of the liquid is calculated based on the output voltage of the amplifier
Implementation Method 2
polarization of the components constituting the liquid is promoted. As a result, an oxidation product or gas is produced on the surface of the electrodes
Implementation Method 3
electrolysis of the water in the liquid and polarization of the components constituting the liquid is promoted
Data Source
AI summary
The resistance detection sensor is configured to detect the electrical resistance value of a liquid. This resistance detection sensor includes a pair of electrodes, a DC voltage application unit, an AC voltage application unit, and a control unit. The pair of electrodes are immersed in a liquid. The DC voltage application unit applies a DC voltage having a first polarity between the pair of electrodes. The AC voltage application unit applies an AC voltage between the pair of electrodes. The control unit calculates the electrical resistance value of the liquid, in a state where the DC voltage is applied between the pair of electrodes by the DC voltage application unit. The control unit controls the AC voltage application unit so as to apply an AC voltage starting from a second polarity opposite to the first polarity at a predetermined time interval between the pair of electrodes. The time period for which the AC voltage is applied between the pair of electrodes by the AC voltage application unit is not an integer multiple of the cycle of the AC voltage applied between the pair of electrodes.