Two-Electrode Conductivity Meter Non-Contact Electrode Design
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Solution Overview
Problem
Existing two-electrode type electrical conductivity meters face issues with measurement errors due to electrode corrosion and foreign matter adhesion, especially with rod-shaped electrodes, which increase polarization capacitance errors and require expensive platinum black, and measurement errors occur when measuring liquids in metal pipes.
Innovation Solution
A two-electrode type electrical conductivity meter with a non-contact electrode on the measurement tube's outer surface and a contact electrode connected to common potential, using a resistor and sample hold circuits to detect AC signal voltages and calculate conductivity based on amplitude, without direct contact, and employing a look-up table for accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rod-shaped electrodes are used in conventional two-electrode type electrical conductivity meters, then the electrode structure is simple and easy to manufacture, but the contact area with measurement target fluid is small which increases measurement error due to polarization capacitance when foreign matter adheres or corrosion occurs
Solution Approach 1:
The patent transitions from rod-shaped electrodes (1D contact) to plate-shaped electrodes (2D contact area). The plate-shaped electrodes are positioned to face each other with a specific gap, creating a two-dimensional measurement area that increases contact area with the measurement target fluid. This dimensional change resolves the contradiction by providing both manufacturing simplicity and improved measurement precision through increased contact area.
2Reliability
If platinum black is used as the electrode material to prevent foreign matter adhesion and corrosion, then electrode stability is improved, but the manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive platinum black with inexpensive stainless steel or other common metals for the plate-shaped electrodes. While the electrodes may have shorter service life compared to platinum black, the significant cost reduction in manufacturing makes this economically viable. The increased contact area and stable plate structure compensate for potential degradation over time.
3Ease of operation
If rod-shaped electrodes are inserted into metal pipes for measuring liquid conductivity, then the measurement function is achieved, but current flow from electrode to pipe causes measurement error unless they are disposed as far as possible
Solution Approach 1:
The patent introduces an insulating support structure that mediates between the plate-shaped electrodes and the metal pipe. This insulating intermediary prevents direct electrical contact between the electrodes and the conductive pipe wall, eliminating the current leakage path that causes measurement errors. The plate-shaped electrodes can thus be positioned close to the pipe wall for effective measurement without suffering from the electrode-to-pipe current flow problem.
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 configuration reduces measurement errors from electrode corrosion and foreign matter adhesion, eliminates the need for expensive materials, and provides accurate and reproducible electrical conductivity measurements while preventing electromagnetic noise interference.
Implementation Method 1
a measurement tube (1) which is formed of an electrical insulation material and through which a fluid of a measurement target flows
Implementation Method 2
a resistor (R1) of which one end is connected to the first electrode, an AC signal generation portion (4) that inputs an AC signal (V1) to the other end of the resistor
Implementation Method 3
a voltage detecting portion (5) that detects voltages (VH and VL) of a signal (V2) generated in the first electrode
Implementation Method 4
an electrical conductivity calculating portion (62 and 62A) that calculates an electrical conductivity of the fluid based on an amplitude (VH−VL) of the voltages detected by the voltage detecting portion
Data Source
AI summary
An electrical conductivity meter comprises a measurement tube formed of an electrical insulation material and through which a fluid of a measurement target flows, a first electrode formed on an outer peripheral surface of the measurement tube, a second electrode connected to a common potential and in contact with the fluid, a resistor in which one end is connected to the first electrode, a voltage detecting portion that detects voltages of a signal generated in the first electrode due to an input of an AC signal to the other end of the resistor, and an electrical conductivity calculating portion that calculates an electrical conductivity of the fluid based on an amplitude of the voltages detected by the voltage detection circuit.