SU1179097A1 - Electrocontact method of measuring thickness of sheet electroconducting articles - Google Patents

Abstract

Electrocontact METHOD FOR MEASURING TOLVDNY SHEET ELECTRICAL CONDUCTING PRODUCTS, comprising that the measured portion of the article includes an electrical circuit consisting of a current source, probe and meter, and passed through an alternating current of low and high frequencies, characterized in that, in order reduce the measurement, measure the voltage drop in the measured area during the passage of currents of low and high frequencies and the wavelength of the product is determined by the formula 2 4U2 uufia L voltage drop where 1 in the product section when the current x respectively low and high frequencies; L - respectively, 1 absolute magnet with permeability (L and specific electrical conductivity of the product material; W - high frequency value of alternating current.

Description

The invention relates to measuring equipment and can be used for measurements with one-sided access of the thickness of electrically conductive coated, flat products or walls of hollow $ products with non-destructive testing. The aim of the invention is to reduce the measurement time,

The drawing shows a structural diagram of a device that implements Yu electrocontact method for measuring the thickness of sheet conductive products.

A device that implements the electric contact method of the thickness of the sheet 15 of electrically conductive products, contains a section of an open electric circuit, consisting of a series-connected first measuring probe 1, an alternating current source 2, a current-sensing resistor 3 and a second measuring probe 4, and a voltage-variable alternating current meter 5 connected between the outputs of the measuring probes 1 and 4. Product 25 6 is included in the electrical circuit between the measuring probes 1 and 4.

The method is as follows.

Active resistance R _{8 of the} electromotive force of the conducting body to direct current or low frequency current is equal to _{R =} J_ _1_ ^К о 3 S 'where λ is the specific electrical conductivity of the body;

- body length;

S is the cross-sectional area of the body.

With alternating current, when the ^40- wavelength of the electromagnetic field is commensurate with the linear dimensions of the cross section of the electrically conductive body, a surface effect arises in it.

For an electrically conductive plate with * 5 dimensions I x bx2d satisfying condition I? by? d, where I, b, d, respectively, the length, width and thickness of the plate, the resistance Z to alternating current of high frequencies 50 ₌ JL Y Jfe.

_ 2b I Λ where (Ufl is the absolute magnetic permeability of the material;

Cd is the cyclic frequency, it does not depend on m <dl, since, due to the surface effect, the electric current is concentrated almost completely near the plate surfaces.

If we measure the resistance of the plate to the current of low and high frequencies, then we can determine the thickness d;

C = ------- = ΊI - I 2 2 ___— =

L R _o Wjtx-a ft R _n

Z 1 1 ~~ ' ^R o 1 to | U a D.

This expression is equivalent to the formula j.2AU ₂ '11 “AC V to ^ a Y 'where dC ^ is the voltage drop across the plate at an alternating current of high frequency;

A U,] is the voltage drop across the plate with alternating current of low frequency.

To perform measurements, the portion of the electrically conductive coating of a flat product or the wall of a hollow product 6, the thickness of which is to be measured on one side, is connected with two probes 1 and 4 to an electric circuit ¹ , which also contains an alternating current source 2, an alternating current voltage meter 5 and a current-setting resistor 3. The AC source 2, the value of which is set by the resistor · 3, has two fixed frequency values: one. from the low-frequency region in which the current density distribution is uniform in the coating, flat article or wall of the hollow article, another is the high-frequency region in which the current density distribution in the coating, flat article or wall of the hollow article is uneven due to the pronounced surface effect and independence while the resistance of the plot to alternating current from. product thickness

The voltage meter 5 sequentially performs measurements of the values of the voltage drops ASH and aU ^ respectively at low and high frequencies and, using the above formula, determines the measured thickness of the coating, flat product or wall of the hollow product.

Claims (1)

ELECTRIC CONTACT METHOD OF MEASURING THICKNESS OF SHEET ELECTRIC CONDUCTING PRODUCTS, namely, that the measured section of the product is included in an electric circuit consisting of a current source, probes and a meter, and an alternating current of low and high frequencies is passed through it, which is different in order to reduce _{d =} .2 -L—— Δ Щ 1 шра Л ’ 4U. ,, di ₂ - voltage drop in the product area at currents correspondingly low and P-a, Λ high frequencies; respectively. absolute magnetic permeability and electrical conductivity of the product material; value of high frequency AC.