JPS6247544A - Measuring instrument for electric potential difference - Google Patents

Abstract

PURPOSE:To detect a crack of steel or the like by changing over many electrodes in order and constituting in order a couple of electrodes for supplying an electric current and detecting an electric potential difference of adjoining four electrodes. CONSTITUTION:When change-over switches 5a-5d interlocking mutually are positioned at contact points 5a1-5d1 respectively, the electrodes 4a and 4d are made the electrodes for supplying the electric current and connected with a direct-current power source 6, and the electrodes 4b and 4c are made the electrodes for detecting the electric potential difference and connected with an electric potential difference measuring instrument 7. Further, when the interlocking is made and the change-over switches are changed over to the contact points 5a2-5d2, the electrodes 4b-4e are connected in the same way, The mutually adjoining electrodes 4c-4f, 4d-4g and 4e-4h are selected by changing over the switches interlocking in order in this way. Accordingly, since the electrodes are changed over in order with the interlocking changing-over switches and a couple each of electrodes for supplying the electric current and detecting the electric potential difference are constituted of the adjoining four electrodes, the same data as those in case the electrodes are arranged most suitably are obtained even if the accurate position of the crack cannot be grasped in advance and existence or nonexistence of the crack and the depth of the crack of a wide range can be easily detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a potential difference measuring device for detecting the presence or absence of cracks in steel materials and the depth of the cracks.

[Conventional technology]

FIG. 2 is an explanatory diagram showing a conventional potential difference measuring device. In the figure, (1) is the steel material to be inspected, (1a) is the crack that has occurred in the steel material (1), (2) is a pair of current supply electrodes, (3) is the current supply electrode (2), ( 2) A pair of potential difference detection electrodes arranged between them.

Next, the operation of the potential difference measuring device configured as described above will be explained. A pair of potential difference detection electrodes (3), (3) separated by a predetermined distance are brought into contact with the surface of the steel material to be inspected (1) with a crack (1&) interposed in between, and the electrodes are placed outside of each other. A pair of current supply electrodes (2) # (
2) When a predetermined current is supplied, the crack (11) that has formed in the steel material (1) acts as an electrical resistance, and a potential difference occurs at both ends according to the depth of the crack. This potential difference is:
It is taken out through the potential difference detection electrodes (3), (3) and measured by a potentiometer (not shown), and the crack (1
m) is detected as the presence or absence of cracks and the depth of cracks.

In this potential difference measurement, the current supplying electrode (2).

(2) and (3) for potential difference detection, arranging (3) so that the crack (1al) is located between the cracks as shown in the figure is optimal from the viewpoint of potential difference detection sensitivity and stability. In addition, in this case, the potential difference detection electrode (3)
.

(3) and between the current supply electrodes (2), (2), the sensitivity becomes better.

[Problem that the invention seeks to solve]

In the conventional potential difference measuring device configured as described above, in order to increase the sensitivity of potential difference detection, a total of four electrodes (2), (2), and (3) are used for current supply and potential difference detection.
) and (3), but when applying the potential difference method to actual defects, it is often difficult to know the location of the actual defect in advance, so it is necessary to place the electrode at the optimal position. The depth of the crack determined from the measured value was sometimes misjudged.

This invention was devised to solve the above-mentioned problems, and its purpose is to obtain a potential difference measuring device that can reliably and optimally detect information on cracks occurring in steel materials, etc. It is.

[Means for Solving the Problems] The potential difference measuring device according to the present invention arranges a large number of electrodes and sequentially switches them using a changeover switch to connect four electrodes adjacent to each other.
A pair of electrodes for current supply and a pair of electrodes for detecting potential difference are sequentially constructed using regular electrodes, and crack detection can be performed by optimal electrode arrangement.

[Effect]

In the potential difference measuring device according to the present invention, a large number of electrodes are placed in contact with the surface of the object to be inspected, and four multi-contact switches for current supply and potential difference detection are switched in conjunction with each other, and four electrodes adjacent to each other are connected to each other. The two outer electrodes are configured for current supply and the inner two electrodes are configured for potential difference detection, and by sequentially switching them, a wide range of scanning can be performed and cracks can be detected with the optimal electrode arrangement.

[Embodiments of the invention]

FIG. 1 is a configuration diagram of a potential difference measuring device showing an embodiment of the invention. In the figure, (4) is an electrode group, which is composed of eight electrodes (4a) to (4h), but the number of electrodes can be set to an appropriate number as required. (
5a) to (5d) each have a plurality of contacts (in this example, 5
It is a changeover switch with two contacts) that can be switched in conjunction with each other. (6) is a current supply source that supplies direct current;
(7) is a potentiometer, and (8) is a coaxial cable.

Next, the operation of the potential difference measuring device configured as described above will be explained. Changeover switches (5a) that interlock with each other
~(5d) are the contact points (5a+), respectively.

(5b + ), (5c 1), (5d ll), the electrode (4a).

(4d) serves as the current supply electrode, and the DC power supply source (6
), and connected to the electrode (4b), (4cl becomes the potential difference detection electrode and is connected to the potential difference measuring device (7). Next, the abnormal point (5a21.(5b, ), (5c,
), (When switching to 5d21, electrodes (4b) to (4e)
are connected in the same way and switched in sequence,
Mutually adjacent electrodes (4c) to 4f), (4d) to (
4g1. (4s) to (4h) are selected. These changeover switches (!5b) and (5c) are the potential difference measuring device (7).
), but since the potential difference to be measured is minute, a coaxial cable (8) is used for connection. When the positions of the changeover switches (5a) to (5a) are changed as described above, the crack measurement range becomes as shown in Table 1. Therefore, the electrode (
Measurements can be made over a wide range from the position of the electrode (4b) to the position of the electrode (4g) at the optimum electrode spacing and at the optimum current density.
If it is between 4f) and (4g), if a conventional 4-needle electrode structure is placed at positions (4a) to (4d) and the potential difference is measured, the depth of crack (1a) will be incorrectly read. However, with the method of this invention, the changeover switch (5
When a) to (5d) are sequentially switched in conjunction with each other, the contacts (5a5), (5tn), and (5c5).

(At the position 5d51, a crack (1a) is interposed between the electrodes (4g) and (4f) that serve as potential difference detection electrodes,
The potential difference caused by the crack (1a) can be reliably detected, and the depth of the crack can be reliably determined based on this detected potential difference.

Table 1 In the above embodiment, the DC potential difference method was explained, but i! 11. It is also possible to use an AC power source as the current supply source (3) and perform the same process using an AC potentiometric method.

〔Effect of the invention〕

As described above, this invention sequentially switches a large number of electrodes using four interlocking changeover switches, and
Since each electrode is configured sequentially as a pair of current supply electrodes and a potential difference detection electrode, even if the exact location of the crack to be measured is not known in advance, the electrodes can be placed optimally. The same data can be obtained at all times, and the presence or absence of cracks and the depth of cracks can be easily detected over a wide range.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a potential difference measuring device showing embodiments of the present invention, and FIG. 2 is an explanatory diagram of a conventional t-potential measuring method. In the figure, (1) is the steel material to be inspected, (1a) is the crack, (
4al~(4hl is an electrode, <5al~(5ci) is a changeover switch, (6) is a current supply source, and (7> is a potential difference measuring device).

Claims (1)

[Claims] In the potentiometric measurement method for detecting cracks in steel materials, a large number of electrodes are arranged and switched sequentially by four interlocking switches, and each of the four adjacent electrodes is used to supply a pair of current and to detect a potential difference. A potential difference measuring device characterized by sequentially configuring electrode groups to detect cracks over a wide range and with optimal electrode placement.