CZ297790B6 - Circuitry and arrangement of electrodes for measuring thickness of wall made of electrically conducting material - Google Patents

Abstract

The invented circuitry and arrangement of electrodes for measuring thickness of wall made of electrically conducting material are characterized in that the first output of an electric power supply (1) is connected via a contact (4) of the first pole of a four-pole switch (3) to a fist supply electrode (12) of four measuring electrodes and the second output of the electric power supply (1) is connected via a throwing over contact (6) of the second pole of the four-pole switch (3) to a second supply measuring electrode (19), whereby the first input of a voltmeter (2) is connected via the contact (8) of a third pole of the four-pole switch (3) to a first sensing measuring electrode (13) and the second input of the voltmeter (2) is connected via the contact (10) of the fourth pole of the four-pole switch (3) to a second sensing measuring electrode (18). At the same time the contact (5) of the switch first pole is connected with a first supply electrode (14) of four reference electrodes and the contact (7) of the second pole of the four-pole switch (3) is connected to a second supply reference electrode (17) and further the contact (9) of the third pole of the four-pole switch (3) is connected to a first sensing reference electrode (15) and the contact (11) of the fourth pole of the four-pole switch (3) is connected to a second sensing reference electrode (16).

Description

Wiring and arrangement of electrodes for measuring wall thickness of conductive material

Technical field

FIELD OF THE INVENTION The present invention relates to the connection and arrangement of electrodes for measuring the wall thickness of conductive material, such as metal pipes, vessels, and the like, in which compensation of material and temperature influences is utilized and utilizes the electric potential field current in the monitored area, for measuring the wall thickness of the structure made of conductive material.

BACKGROUND OF THE INVENTION

With a sufficiently large distance between the electrodes, the magnitude of the electrical potential drop across the measuring electrodes located between the electrodes is inversely proportional to the thickness measured. The dependence of the voltage drop on the conductor thickness is well known (Ohm's law), but this is not used in practice for the thickness measurement due to the very different resistivity values of the different materials and their considerable temperature dependence. Therefore, other physical principles are used to measure thickness, such as the ultrasonic method, which, however, does not allow measurements at very high temperatures and is also not suitable for long-term continuous measurements.

SUMMARY OF THE INVENTION

These disadvantages are overcome by the connection and arrangement of the electrodes for measuring the wall thickness of the conductive material by the potential method according to the invention, characterized in that the first output of the power source is connected to the first supply electrode of the four measuring electrodes via the first contact of the quadrupole; The power supply electrode is connected to the second supply electrode via the changeover contact of the second pole of the switch. At the same time, the first voltmeter input is applied to the first sensing metering electrode via the third pole contact of the switch and the second voltmeter input is applied to the second sensing metering electrode via the fourth pole contact of the switch. The switch first pole contact is coupled to the first reference electrode reference electrode and the second switch pole contact is coupled to the second reference reference electrode, and the third pole switch contact is coupled to the first scanning reference electrode and the fourth pole contact is coupled to the second scanning reference electrode .

To eliminate the above disadvantages, the invention utilizes four additional reference electrodes, wherein the supply electrodes are positioned close enough together so that the voltage on the reference sensing electrodes practically does not depend on the measured thickness. However, this stress is proportional to the resistivity of the material, which also exhibits temperature dependence. By comparing the measured voltages on the sensing measuring and reference electrodes, we can evaluate a parameter that does not depend on the material properties or the temperature of the material, but only on its thickness.

Overview of the figure in the drawing

The invention is illustrated in detail by means of a drawing, in which the connection between the individual elements and the electrodes is illustrated, in which the distribution of the individual electrodes is defined.

DETAILED DESCRIPTION OF THE INVENTION

The wiring and arrangement of the electrodes for measuring the thickness of the conductive material in the exemplary embodiment according to the invention consists of a current source 1, the first output of which is connected via the contact 4 of the first pole of the four-pole switch. contact 6 of the second pole of the switch 3 is applied to the second power supply electrode 19. The first input of the voltmeter 2 is applied to the first sensing electrode 13 via the third pole contact 8 of the switch 3 and the second input of the voltmeter 2 at the same time, the first pole contact 5 of the switch is coupled to the first electrode reference electrode 14 and the second pole contact 7 of the switch 3 is coupled to the second electrode reference electrode 17. Further, the third pole contact 9 is and the fourth pole contact 11 of the switch 3 is connected to the second scanning reference electrode 16.

With a sufficiently large distance between the supplying electrodes 12 and 19, when d4 > 2t and at the same time the distance between the electrodes 12 and 13 respectively. 18 and 19 satisfy the condition ml > m2> t, the electric field has a planar character and the voltage U (M) on the measuring electrodes is inversely proportional to the material thickness t at the given location:

K t = ------- U (M)

However, constant K depends on the resistivity of the material, including its temperature dependence. To eliminate these effects, the invention utilizes the electric potential field properties around the reference electrodes, where the spacing of the power reference electrodes 14 and 17 is d2 < 2t. This field is rather spatial in nature and the voltage drop U (R) between the sensing reference electrodes 15 and 16, whose distance from the supply electrodes satisfies condition r1 <0.5d2 and condition r2 <0.5d2, is practically no longer dependent on the measured thickness:

U (Rj ~ const.

However, this stress is directly proportional to the specific resistance of the material in the monitored area, including its temperature dependence. If we evaluate the parameters according to the following relation:

U (M) A = ---------,

U (R) we obtain a quantity that is inversely proportional to the thickness t and is not dependent on the electrical properties of the measured material, including temperature dependence:

X / t = ------ + K ₂ .

AND

The constants K _: and K ₂ depend on the specific electrode placement and distance values d, d2, ml, m2, r1, r2. For a particular electrode arrangement, the values of the constants X / and K ₂ can be determined by calibration, which remains valid when measuring the thickness of other materials.

-2GB 297790 B6

Industrial applicability

The proposed connection allows long-term, continuous monitoring of wall thickness changes in operating conditions and in inaccessible places, which can be exposed to very high temperatures (up to 600 ° C). It also improves the stability and reproducibility of long-term measurements of more than 10x. The wiring is particularly suitable for monitoring corrosive material losses in pipes, containers and the like.

Claims (1)

PATENT CLAIMS Wiring and arrangement of electrodes for measuring the wall thickness of conductive material, characterized in that the first output of the current source (1) is connected to the first supply electrode (12) of the four measuring electrodes via the first pole contact (4) of the four-pole switch (3). and the second output of the source (1) is connected to the second supplying electrode (19) via the changeover contact (6) of the second pole of the switch (3), the first voltmeter input (2) being connected via the third pole contact (8) of the switch (3) the first sensing electrode (13) and the second voltmeter input (2) are connected through the fourth pole contact (10) of the switch (3) to the second sensing electrode (18), at the same time the first pole contact (5) is connected to the first the electrode reference electrode (14) and the second pole contact (7) of the switch (3) is connected to the second power reference electrode (17) and further is the contact (9) the third pole of the switch (5) is connected to the first sense reference electrode (15) and the fourth pole contact (11) of the switch (3) is coupled to the second sense reference electrode (16).