Field of the invention

The invention relates to a measuring probe applicable in the field of non-destructive diagnosis of steels, in particular refractory steels, by means of determination and evaluation of the anisotropy of the impedance spectrum.

Background of the invention

The impedance spectrum is the output of an impedance spectroscopy measurement. Impedance spectroscopy is an experimental measurement method that can be used to determine the properties of the system under study, such as the structure of an alloy. The measurement method is based on transmitting a sinusoidal electrical voltage signal through the sample to be measured (e.g. alloy-steel) and then measuring the complex impedance Z as a function of frequency f. The measured results are subsequently evaluated by analytical and empirical procedures, thus providing a non-destructive diagnosis of the measured sample. One of the evaluation procedures of the impedance spectrum can be the so-called anisotropy evaluation. Anisotropy is the dependence of the quantity of interest on the choice of direction. To evaluate anisotropy, it is necessary to send a signal in at least two mutually perpendicular directions for the measured sample. From the differences in the recorded signal waveforms, information about the anisotropy of the measured sample can be deduced.

Diagnostics using impedance spectroscopy is useful in industry, where it is necessary to check the quality and technical condition of new products, or where it is necessary to check the technical condition of operating equipment, such as pipelines in the power industry.

Examples of the application of impedance spectroscopy in non-destructive diagnostics are the inventions of documents GB 2 289 338 A, US 5 202 641 A, and US 7 443 177 B. These examples use a standard four-electrode circuit (so-called Kelvin circuit), both for permanent installations with welded electrodes (GB 2 289 338 A) and for measurements using portable measuring probes (US 5 202 641 A, US 7 443 177 B). These inventions are not suitable for evaluating the anisotropy of the impedance spectrum, since they cannot be used to measure signals in the required mutually perpendicular directions in a single attachment.

The purpose of the invention is to create a measuring probe for non-destructive diagnosis of steels, in particular refractory steels, by means of determination and evaluation of the anisotropy of the impedance spectrum, which would be able to perform the necessary measurements for the evaluation of the anisotropy within a single application to the sample to be measured, without distortion of the measured data by changing the position of the probe relative to the sample to be measured or by the influence of parasitic inductive impedance.

Summary of the invention

The task is solved by creating a measuring probe according to the invention described below.

The measuring probe for non-destructive diagnostics of steels, especially refractory steels, is intended for use in the method of determination and evaluation of the anisotropy of the impedance spectrum. The measuring probe consists of a body which gives the measuring probe the characteristics of a rigid body and at the same time the body serves as a sheath and cover for the electrical components. It further comprises at least one interconnection cable for connecting the measurement probe to the measuring apparatus. The measuring probe further comprises at least one pair of excitation electrodes for introducing a sinusoidal electrical voltage signal from the measuring apparatus into the sample to be measured, and at least one pair of sensing electrodes for transmitting information about the waveform of the sinusoidal electrical voltage signal through the sample to the measuring apparatus.

The subject matter of the invention is that a pair of excitation electrodes and a pair of sensing electrodes are arranged in a measuring probe body for simultaneous attachment to a sample to be measured, the arrangement of the electrodes being tetragonal. The simultaneous attachment of the electrodes in a tetragonal arrangement to the sample to be measured ensures that measurement distortion during the introduction and collection of the electrical voltage signal is not introduced due to inaccurate attachment outside the tetragonal arrangement of the electrodes. The tetragonal arrangement of the electrodes ensures a perpendicular direction of transmission of the electrical voltage signals. The advantage of the measuring probe according to the invention is that it only needs to be attached, since the electrodes used to perform the measurement are already suitably arranged relative to each other, thus the user of the measuring probe does not need to check the relative arrangement of the electrodes. At the same time, the body of the measuring probe is provided with at least one means for fixing the attachment of the measuring probe to the sample to be measured. The measuring probe shall not be moved before the measurement is completed to avoid distortion of the results.

Preferably, one arbitrary electrode in the probe body is cushioned for attachment to the sample to be measured with a curved surface. This is particularly practical in the case of in-situ probe applications where the properties of steels, particularly various pipelines, with different curved surfaces are measured.

It is also advantageous that the connecting cable is six-wire. Although it is practically possible to change the role of the electrodes in a tetragonal arrangement by means of a switching system to change the direction of the electrical voltage signal, it is much more convenient to use a six- wire cable to connect the measuring probe to the measuring instrument, so that the influence of the parasitic inductive impedance on the resulting measurement is not so serious.

Last but not least, it is advantageous if the means for fixing the attachment comprises at least one magnet or clamping screw. Fixing by means of a magnet is very comfortable. The magnet holds the measuring probe in place for the entire measurement period, while allowing the user to work with the measuring probe quickly and easily. If it is not possible or convenient to use a magnet, the measuring probe can be attached to external structures using a clamping screw, creating a solid, disassembled connection.

Advantages of the probe include easy attachment and removal from the sample to be measured, the possibility to be used on curved samples, the possibility to allow measurement in a single application, and a simple design with low manufacturing costs. A further advantage of the measuring probe according to the invention is that it allows to increase the sensitivity of the diagnostic method by evaluating the impedance spectrum and its anisotropy. The use of the measurement probe according to the invention reduces measurement uncertainties for diagnosis. The use of the measuring probe according to the invention brings savings from the possibility of safe operation of components in the energy industry even after their planned lifetime.

Brief description of the drawings

The invention will be explained in more detail in the following illustrations, where:

Figure 1 shows an axonometric top view of the measuring probe,

Figure 2 shows an axonometric bottom view of the measuring probe,

Figure 3 shows selected electrode configurations in the measuring probe,

Figure 4 shows the wiring diagram of the measuring probe and the measuring instrument.

Example of a preferred embodiment of the invention

It shall be understood that the specific embodiments of the invention described and illustrated hereinafter are presented for purposes of illustration and not as a limitation of the invention to the examples provided. Those skilled in the art will find or will be able to provide, using routine experimentation, a greater or lesser number of equivalents to the specific embodiments of the invention described herein.

The present of embodiment of the measuring probe j_ according to the invention enables the measuring apparatus connected thereto to determine the anisotropy of the impedance spectrum of refractory steels by the alternating potential method during one application of the measuring probe 1_ to the measured sample. The operation of the measuring probe 1_ is very simple, since the measuring probe 1_ is held in place by the base with the protruding electrodes 5 against the sample to be measured and is fixed in place by the attractive force of the magnet 7 to the sample to be measured. The attractive force of the magnet 7 is sufficient to fix the measuring probe 1, but at the same time is easily overcome by the user of the measuring probe 1, so that the user of the measuring probe 1 can easily attach and remove the measuring probe 1 as required.

Figure 1 and Figure 2 show a measuring probe 1 having a body 4 of a cube-like shape. On the upper base of the measuring probe 1_ (see Figure 1), there is a screw 2 visible for clamping the measuring probe j_ to an external device not shown. The external device may be, for example, a telescopic pole for attaching the measurement probe 1 at heights out of reach of the user.

A magnet 7 is shown on the lower base of the body 4 of the measuring probe 1 (see Figure 2), which serves to fix the measuring probe 1_ to the sample to be measured.

Further, four electrodes 5 are visible on the lower base of the measuring probe 1 protruding above the lower base to prevent contact between the lower base of the measuring probe 1 and the sample to be measured. The electrodes 5 are bent at the free ends, one of the electrodes 5, although not visible in Figure 2, being resiliently anchored in the measuring probe 1, while the remaining electrodes 5 are rigidly anchored in the measuring probe 1.

As for the body 4 of the measuring probe 1, it is a rigid body, and it also includes a cover 3. The cover 3 has an opening 6 (see Figure 2) for the passage and fixation of the not shown connecting cable 8. The cover 3_can be removed to allow the electrodes 5_to be connected to the conductors of the jumper cable 8. In the folded state of the measuring probe 1, the cover 3 is joined with the body 4^of the measuring probe l_to form a single unit. The body 4_i s made of a plastic material which meets two basic requirements, namely electrical insulating properties and good machinability.

Based on routine work, those skilled in the art would be able to design different body shapes 4 of the measuring probe 1, either according to ergonomic requirements for a more comfortable grip in the user's hand, or according to the requirements of specific in-situ measurements. Figure 3 shows the configurations of 10, 11, 12 and 13 pairs (CP, SP, CN, SN) of electrodes 5 in a tetragonal arrangement for making measurements. The electrodes 5 are divided into an excitation pair (CP, CN) and a sensing pair (SP, SN).

In the configuration 10 labeled "A", the sensing pair (SP, SN) and the excitation pair (CP, CN) lie parallel in a tetragonal arrangement. The electrical voltage signal is transmitted in the axis of the excitation pair (CP, CN), in the so-called main direction. Since the excitation (CP) electrode 5 is spring loaded, it can be deflected from its nominal position in one of the indicated directions dl to d8. If a measurement were to be made for anisotropic evaluation, it would be necessary to rotate the measuring probe 1_ by 90°. However, this is undesirable because it is not guaranteed that the measuring probe j_ will be attached to the exactly same location on the surface of the measured sample and, in addition, the spring electrode 5 may be deflected from its nominal position in another direction dl to d8, which will result in measurement uncertainty.

In configuration 11, labeled "B", the sensing pair (SP, SN) and the excitation pair (CP, CN) lie in diagonals of a tetragonal arrangement. The electrical voltage signal is transmitted in the axis of the excitation pair (CP, CN), in the so-called perpendicular direction. This configuration 11 is an example of the possibility that the measuring probe l_is provided with a complex switching system that reverses the roles of the electrodes 5 without removing the measuring probe 1 from the measured sample. Even this solution is not optimal from the point of view of measurement uncertainty, since parasitic inductive impedance is a significant factor.

In the configuration 12 labeled "D", the sensing pair (SP, SN) and the excitation pair (CP, CN) lie parallel in a tetragonal arrangement. The electrical voltage signal is transmitted in the axis of the excitation pair (CP, CN), in the so-called perpendicular direction. In this case, the evaluated quantity in the perpendicular direction is the impedance spectrum.

In the configuration 13 with the designation "H", an interchange of electrodes 5 in the sensing pair (SP, SN) and in the excitation pair (CP, CN) is indicated. In this case, the evaluated quantity in the perpendicular direction is the impedance spectrum of the anisotropy measure. Figure 4 shows a schematic of the connection of the measuring probe 1 and part 9_of the measuring instrument using the connecting cable 8. The interconnecting cable 8 is a six-wire cable, so that the function of the electrodes 5 can be changed without increasing the parasitic inductive impedance.

Industrial applicability

The measuring probe for non-destructive diagnostics of steels according to the invention is applicable in the fields of measurement and testing, in particular when performing in-situ diagnostics of refractory steels.

List of positions and symbols used in the drawings and in the description

1 measuring probe

2 screw for tightening the measuring probe body and for connection to external structures

3 cover with cavity for connecting the connection cable

4 probe body

5 electrode

6 hole for the passage and fixation of the connecting cable

7 magnet

8 connecting cable

9 part of the measuring instrument with switch

10 Configuration A (measurement in the main direction)

11 Configuration B (measurement in perpendicular direction)

12 Configuration D (measurement in perpendicular direction)

13 Configuration H (measurement in perpendicular direction)

SP positive sensing electrode

SN negative sensing electrode

CP positive excitation electrode

CN negative excitation electrode dl- d8 possible directions of deviation of the flexible electrode