SU578558A1 - Method of checking thickness of dielectric coating - Google Patents

Description

one

The invention relates to non-destructive testing of materials and products, in particular, methods of controlling the parameters of electrically conductive products by the eddy current method.

A known method of controlling the thickness of dielectric coatings from an electrically conductive base, which consists in exciting a product with eddy current transducer mounted on it using eddy currents, measuring the resistance introduced into the converter and measuring the thickness of the dielectric coating

one.

However, measuring the thickness of dielectric coatings in this way with non-specific electrical resistivity of the product leads to significant errors, and measuring the specific electrical resistance of the product is almost impossible.

There are also known methods for monitoring electrical resistivity, which consist of exciting an eddy-current transducer, included in an oscillating circuit, with eddy currents in an electrically conductive product, measuring the value of the impedance into the resistance, and judging its value for the electrical resistivity of product 2.

However, these methods do not give precise results in the presence of dielectric coatings of considerable thickness and with a change in the distance between the transducer and the product.

The closest technical solution to the invention is a method for controlling the thickness of dielectric coatings on an electrically conductive base, which consists in exciting through an eddy-current transducer transducer eddy currents, the frequency of which is chosen from

a cojio / p l,

where a is the radius of the transducer; ω is the circular frequency; io is a magnetic constant; p is the specific electrical coupling, the active and reactive components of the emf introduced into the converter are distinguished, they are summed up and the crowd is judged by the magnitude of the voltage produced;

The disadvantage of this method is the inability to control the electrical resistivity.

The aim of the invention is the simultaneous measurement of the thickness of dielectric coatings on an electrically conductive product and the electrical resistivity of the product.

Claims (3)

To do this, according to the proposed method, eddy currents are additionally excited at the base, the frequency of which Zstana: is infused from a soc / p condition, the active component of the emf applied at this frequency is separated, and the voltage divider is output from the voltage divider In this case, the normalized active component of the applied EMF at the second frequency and the value of the obtained ratio determines the value of the specific electrical resistance. According to the proposed method, the control of the thickness of the dielectric coatings on the electrically conductive product and the electrical resistivity of the base is carried out as follows. Using an overhead eddy current transducer mounted on the product, in a conductive product, eddy currents of two frequencies are excited, one of which is chosen from the condition of / r, and the other from the condition of a2 soc / p. For example, the active and reactive components of the induced electromotive force on the first frequency and the active component on the second are isolated using phase-sensitive detectors. The active and reactive components of the applied emf at the first frequency are summed up using the pressure sensor and the magnitude of the voltage obtained, judging the thickness of the coating. With the help of a voltage divider, the voltage from the output of the adder to the voltage proportional to the active component of the EMF at the second frequency is divided, and the value of the electric resistance of the terminal is determined by the value of the obtained ratio. This method allows much more accurate control of the thickness of dielectric coatings on an electrically conductive product and the specific electrical resistance of the product in a large range of monitored parameters. Claims The method of controlling the thickness of dielectric coatings on an electrically conductive base, is that with the aid of an overlay eddy current transducer, eddy currents are excited at the base, the frequency of which is set by the condition cojio / p - l, where a is the transducer radius; ω is the circular frequency; Yao - magnetic constant; p is the electrical resistivity, the active and reactive components of the applied EMF are separated, they are summed up and, judging by the magnitude of the voltage received, they judge the thickness of the coating, characterized by the fact that, in order to control the electrical resistivity of the base, the vortex The currents whose frequency is established from the condition a coj-io / p Cl separate the active component of the EMF applied at this frequency, using the voltage divider to divide the voltage from the output of the adder to a voltage proportional to tive component of the emf applied at the second frequency, and judging by the magnitude of the obtained ratio, the electrical resistivity value is judged. Sources of information, taken into consideration and examination 1.Dorofeev A.L. Nonconstructive testing by eddy current method. M., Oborongiz, 1961, p. 114 2. In the same place 100. 3. USSR author's certificate No. 292057, cl. Q 01B 7/04, 1969.