SU631812A1 - Electrochemical transducer - Google Patents

Description

one

This invention relates to a technique for measuring the oxygen content in gaseous and liquid media, namely to electrochemical sensors. It can be used in the mining, chemical and metallurgical industries.

Electrochemical sensors are known, the cathode assembly of which is made in the form of a wall of noble metal and a polymer membrane facing the analyzed medium flj.

This sensor has significant drawbacks.

Thus, the mesh cathode pressed against the membrane from the side of the electrolyte becomes less sensitive with time due to the unsteady tension of the thermal membrane. Such a cathode does not efficiently trap oxygen due to the diffusion of a part of it through the grid cells deep into the electrolyte.

The output signal of the sensor depends on the speed of movement of the analyzed medium due to the change in the thickness

diffusion layer adjacent to the polymer membrane from the environment.

The sensor has a large time constant and low accuracy due to different distances of the grid sections, the thickness of which is equal to two diameters of the wire from which it is woven, from the membrane, i.e. due to the varying thickness of the diffusion cathode layer in the electrolyte.

Big margin in results

the measurement is explained by a certain dependence of the limiting oxygen reduction current on the potential of the grid cathode in galvanic type sensors,

those. the slope of the site of the current limit on the current-potential curve.

The closest technical solution to the proposed is a galvanic sensor containing a wire cathode, a polymer membrane and a rigid perforated sleeve 2j.

Cathode assembly mounted in the butt

hermetic cylindrical body made of organic fiber. Second butt

made of zinc, which is both a lid and an anode anode electrode, the gap between the cathode assembly and the zinc anode is filled with an electrode, O, IK, KOH solution. The position of the agulka, which presses the mesh cathode to the membrane, is changed with a screw. For this purpose, there is a threaded hole in the center of the zinc anode.

This sensor of a mine oxygen analyzer has a large relative error in measuring the oxygen content of 2.5% (the absolute error is to, 5%). The purpose of the invention is to improve the accuracy and stability of the sensor, reducing its inertia. This goal is achieved by providing the sensor with a soft gas-permeable substrate located between the rigid perforated sleeve and the polymer membrane. The perforated bushing is made in the form of a tiller and the cathode is made in the form of a wire coil wound with a wire turn to a coil with tension. Replacing the grid, with a single-layer coil wound from one turn to another, makes it possible to increase the working surface of the cathode with the same dimensions of the visible surface due to the elimination of grid openings, i.e. increase sensor output. The single-layer coil, in addition, has a smaller thickness than a woven wire mesh of the same diameter. This provides a more uniform access to any areas of the cathode to diffuse oxygen and a more uniform distribution of the potential between the sections of the cathode, which reduces the dependence of the limiting, current of recovery of oxygen on the potential of the cathode. The presence of a soft layer - tissue. gaskets — between a rigid perforated cylinder and a polymer film, on which a single-layer cathode coil is wound, also contributes to a more uniform access to cathode sections of oxygen diffusing through the film due to the contact of the coil turns to the polymer film. This also reduces the sensor time constant due to the reduction in thickness of the diffusion layer between the cathode and the polymer film.

The presence of a hollow perforated cylinder, the cavity of which is facing the medium being analyzed, and a soft layer of tissue gasket are on it. contribute to the stabilization of the diffusion layer in the analyzed medium and reduce the dependence of the output signal on the velocity of the analyzed medium.

The drawing shows the proposed electrical sensor.

Claims (3)

The cathode assembly, hermetically mounted into the Plexiglas body 1, is made in the form of a cylinder 2. The side surface of the cylinder is covered with a continuous layer of nylon fabric 3, hermetically welded along the forming plastic film 4, on which a single-layer coil of platinum wire is wound to the turn. Inside the housing there is a zinc ring anode 6 adjacent to the internal machine of the cylindrical sensor housing. The space between the anode and the cathode assembly is filled with electrolyte (0, lNaAc with the addition of NaOH to pHVE). Through the case, the anodic and cathodic terminals 7, to which; An indicator instrument, an ammeter (milli-, microammeter tr), is connected. The output signal of the proposed sensor was amplified by 3 times, and the absolute error was 0.2%, the maximum time for setting the output signal was no more than 2 minutes. The sensor readings do not depend on the speed of movement of the medium being analyzed — both the nitrogen-oxygen gas mixture and water with oxygen dissolved in it. 1. Electrochemical sensor comprising a wire cathode, a polymer membrane and a rigid perforated sleeve, characterized in that, in order to improve the accuracy and stability of measurements and reduce inertia, it is provided with a soft gas-permeable substrate located between the rigid perforated sleeve and the polymer membrane, perforated sleeve is made in the form of a cylinder, and the cathode is made in the form of a wire coil. 2. The sensor according to claim 1, about tl and h ayush and with the fact that the coil is wound wire coil to turn. 3. The sensor PP. 1, 2, and the wire with the coil is wound with tension. Sources of information taken into account in the examination: 1. Epeggrohpmn, v. 5 vol. 1, p. 1303, 1969. 2. Mining Journal 1971, No. 3, p. 65. S. "