JP3752541B2 - Electric field detection probe and three-dimensional electric field measurement method using the probe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in an electric field detection probe and a three-dimensional electric field measurement method using the probe.
[0002]
[Prior art]
Conventionally, as an electric field measurement method in liquid, for example, a probe that bends the tip of a coaxial cable vertically, exposes the tip of the inner conductor and the outer conductor at a certain distance at the tip, and measures the electric field therebetween. It was used.
[0003]
FIG. 1A and FIG. 2 show a conventional probe (see Non-Patent Document 1 and Non-Patent Document 2). FIG. 1B is an enlarged view of the probe shown in FIG. In the figure, 1 is a probe, 1A is a shaft portion, 1B is a horizontal portion bent vertically in an L shape with respect to the shaft portion 1A, 2 is a tip exposed portion of the inner conductor, 3 is a tip exposed portion of the outer conductor, 4 Reference numerals 5 denote probe output terminals connected to the inner conductor and the outer conductor, respectively. Reference numeral 15 denotes physiological saline, 16 denotes a container, 17 denotes a table on which the container 16 is placed, 18 denotes an electric field generating coil for generating a potential in the physiological saline 15, and 19 denotes a probe fixing frame. In addition, since the thing with the same referential mark of this specification and drawing shows the same function, description is abbreviate | omitted.
[0004]
In both probes of FIGS. 1 and 2, the inner conductor 2 and the outer conductor 3 are exposed at an interval of about 1 cm. Then, the electric field difference (V / m) between the outer conductor and the inner conductor is calculated by measuring the potential difference (V) between the outer conductor and the exposed end of the inner conductor with an oscilloscope or the like. The electric field generating coil 19 is for generating an electric field in the physiological saline 16 and testing the function of the probe 1.
[0005]
Furthermore, in a circularly polarized wave and linearly polarized wave primary primary radiator, an L-shape that detects an electric field by rotating so as to be coupled to the electric field direction of the desired electromagnetic wave for detecting the electric field of the horizontally polarized wave and the vertically polarized wave. There is a type probe (see Patent Document 1, for example).
[0006]
[Non-Patent Document 1]
PJ Maccabee, VE Amassian, RQ Cracco, JB Cracco, L. Eberle and A. Rudell, Stimulation of the Human Nervous System Using the Magnetic Coil, Journal of Clinical Neurophysiology, Vol. 8, No. 1 (1991) p 38-55
[Non-Patent Document 2]
Makoto Kobayashi, Shoogo Ueno, Takahide Kurokawa, Importance of soft tissue inhomogeneity in magnetic peripheral nerve stimulation, Elecrtroecnephalography and clinical Neurophysiology, 105 (1997), p406-413
[Patent Document 1]
JP-A-5-83004 [0007]
[Problems to be solved by the invention]
However, the conventional probe has two problems. One is that the electric field can be measured only in one plane (XY plane) by rotating around the Z axis in FIG. 1, and the second is that the length of the L-shaped horizontal part (see FIG. A circular region having a radius of 1 (b) is essential for the measured side. This rotation of the probe disturbs the area to be measured and can possibly destroy it. In particular, when measuring an electric field in a living body, the cell is cut, so it cannot be used.
[0008]
[Means for solving problems]
In order to solve the above problems, the electric field detection probe of the present invention is characterized in that the exposed end portions of the inner conductor and the outer conductor of the coaxial cable are exposed from the tip surface inclined with respect to the central axis.
[0009]
Furthermore, the three-dimensional measurement method of the present invention is such that the tip portions of the inner conductor and outer conductor of the coaxial cable are exposed from the inclined surface with respect to the central axis, and an electric field detection provided with an engagement member that enables the tip portions to rotate. The three-dimensional electric field is measured by detecting the electric field at the position where the probe is rotated 90 degrees and 180 degrees from the initial position.
[0010]
Since the structure of the L-shaped horizontal part of the probe is eliminated, it can be inserted into the measurement area from one direction, and the electric field can be detected in three orthogonal directions in the micro area by rotating the probe axis without disturbing the measurement area. Become. The calculation of the measurement electric field of the present invention can be obtained only by the four arithmetic operations of the detected potential difference, and the respective three-dimensional orthogonal components can be obtained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the examples of FIGS.
FIG. 3 is a conceptual diagram of the electric field detection probe 1A (cross section) of the present invention. In the figure, 1A is a probe, 6 is an internal conductor, 7 is an external conductor (mesh-like), 8 is an insulating material, and 9 is an insulating coating. These configurations constitute a coaxial cable. Reference numeral 10 denotes an insulating / adhesive / fixing material (adhesive) for fixing and insulating other than the exposed conductor at the tip of the probe, and 11 denotes a probe casing.
[0012]
The exposed end portion 2 of the inner conductor of the coaxial cable and the exposed end portion 3 of the outer conductor are exposed a predetermined distance from the end face 11B inclined with respect to the central axis. Except for the tip exposed portion at the tip of the probe, it is insulated from the outside by 10 insulating / adhesive / fixing materials (adhesive) and embedded in the probe casing 11. 11A is an engaging member engaged with a rotation mechanism for rotating the probe 1A around the central axis of the coaxial cable.
[0013]
Only a part of the outer conductor (mesh-like conductor) 7 is processed into a linear shape to constitute a tip exposed portion. In the example of FIG. 3, the tip exposed portions 2 and 3 are arranged at positions around the coaxial cable diameter in order to increase the distance between the tip exposed portions 2 and 3. The tip exposed portions 2 and 3 may be configured by extending the inner conductor and the outer conductor as they are.
[0014]
FIG. 4 is a schematic diagram of a configuration example of an electric field measurement device using the electric field detection probe 1A of the present invention. 20 is a measurement area, 21 is a probe fixing frame, 22 is a coaxial cable, 23 is an oscilloscope equipotential measuring device, 24 is an arithmetic recording device, 25 is a rotation / support device that supports the probe 1 and rotates it around the probe vertical axis. Represents. Note that the waveform shown in the figure displayed on the potential measuring instrument (oscilloscope) 23 is a waveform when an electric field induced in the measurement area by a pulse current flowing through the electric field generating coil 18 is measured. A terminal coaxial cable 22 of the probe coaxial cable is connected to a potential measuring device 23.
[0015]
FIG. 5 is a diagram for explaining the principle of the electric field measurement method using the electric field detection probe of the present invention. FIG. 5A shows a defined probe coordinate system. The central axis direction of the probe is the Z-axis, and the axis perpendicular to the Z-axis on the plane including the straight line and the Z-axis passing through the intersection O of the straight line connecting the probe tip exposed portions 2 and 3 and the Z-axis is the X-axis. The Z axis and the axis perpendicular to the X axis passing through the intersection are defined as the Y axis (in the figure, the Y axis direction is the direction away from the paper surface). The intersection is the origin of the coordinate system. The inclined tip surface 11B is a surface parallel to the Y axis. Ex, Ey, and Ez represent components in the X-axis direction, Y-axis direction, and Z-axis direction of the electric field required in the measurement area.
[0016]
5B shows the initial position of the probe, FIG. 5C shows the position of the probe rotated 90 degrees around the Z axis from the initial position, and FIG. 5D shows the position of the probe rotated 180 degrees around the Z axis. The state at is shown. The potential differences between the tip exposed portions 2 and 3 at the initial position, the position rotated 90 degrees, and the position rotated 180 degrees are represented by V ₁ , V ₂ , and V ₃ , respectively. The potential differences V ₁ , V ₂ , V ₃ can be expressed by the following formulas (1) to (3) based on the X-axis component Vx, the Y-axis component Vy, and the Z-axis component Vz.
[0017]
V ₁ = Vx + Vz (1)
V ₂ = Vy + Vz (2)
V ₃ = −Vx + Vz (3)
[0018]
Based on the formulas (1) to (3), Vx, Vy, and Vz are obtained by the following formulas (4) to (6).
Vx = (V ₁ −V ₃ ) / 2 (4)
Vy = V ₂ − (V ₁ + V ₃ ) / 2 (5)
Vz = (V ₁ + V ₃ ) / 2 (6)
[0019]
Based on the equations (4) to (6), the X-axis component Ex, the Y-axis component Ey, and the Z-axis component Ez of the target electric field are obtained by the following equations (7) to (9). Here, b is a distance (m) between the tip exposed portions, and θ is an angle (degree) formed by a straight line connecting the probe central axis (Z axis) and the tip exposed portion.
Ex = Vx / (b · sin θ) (7)
Ey = Vy / (b · sin θ) (8)
Ez = Vz / (b · cos θ) (9)
[0020]
First, the potential difference between the tip exposed portions is detected at the initial position of the probe (FIG. 5B). The resulting value is V _1. Similarly, potential differences V ₂ and V ₃ between the tip exposed portions are detected at the 90 ° rotation position (FIG. 5C) and the 180 ° rotation position (FIG. 5D), and the equations (4) to (6) are detected. Thus, axial potentials Vx, Vy, and Vz are calculated. The X-axis, Y-axis, and Z-axis components Ex (V / m), Ey (V / m), and Ez (V / m) of the electric field are calculated by the equations (7) to (9). This electric field is the electric field at the origin of the coordinate system.
[0021]
In the apparatus shown in FIG. 5, the probe 1A of the present invention is engaged with a rotating mechanism by an engaging member 11A provided when necessary. The probe is driven around the Z axis by 90 degrees and 180 degrees by the rotation instruction device. The three-dimensional orthogonal component of the electric field is calculated and stored in the calculation / recording device 24 for the detected potential difference at the initial position of the probe, 90 ° rotation and 180 ° rotation positions.
[0022]
FIG. 6 shows an example in which the electric field in one direction (Ex direction) measured with a conventional probe is used as a reference and the result of the probe according to the present invention is compared. Using a thin coaxial cable (SUMITOMO SS753201) with an outer diameter of 1.3 mm, the distance between the outer conductor of the conventional probe and the exposed end of the inner conductor is 9 mm, and the tip of the outer conductor and inner conductor of the probe of the present invention The distance (b) between the exposed portions is about 2.4 mm, the inclination angle (θ) is about 60 degrees, and the outer diameter of the probe casing is about 2.4 mm.
[0023]
The horizontal axis represents the electric field Ex in one direction (X axis) measured using the conventional probe, and the vertical axis represents the electric field measured using the probe of the present invention. The relationship between the two was almost linear, and the regression analysis coefficient was 1.05. These can be more accurately detected by calibration. The same applies to the potentials Vy and Vz in other directions.
[0024]
【The invention's effect】
As described above, the electric field detection probe of the present invention can measure electric fields in three orthogonal directions by rotating the shaft 180 degrees only by inserting the object into the measurement object from one direction. Further, by reducing the diameter of the probe (diameter 0.6 mm, etc.), it is possible to measure in a finer region. There is less possibility of disturbance of the measurement area due to the rotation of the probe, and in some cases destruction. For example, when measuring the electric field of the mouse brain, the electric field could be measured effectively without cutting the brain cells.
[Brief description of the drawings]
FIG. 1 shows an example (part 1) of a conventional electric field detection probe.
FIG. 2 shows a second example of a conventional electric field detection probe.
FIG. 3 is a conceptual diagram of a cross-sectional view showing an embodiment of the present invention.
FIG. 4 shows an example of a three-dimensional measuring apparatus according to the present invention.
FIG. 5 is a diagram illustrating the principle of a three-dimensional electric field measurement method according to the present invention.
FIG. 6 shows a comparative example of a detection electric field.
[Explanation of symbols]
1 Probe (conventional type)
1A Probe 2 Coaxial cable inner conductor tip exposed portion 3 Coaxial cable outer conductor tip exposed portion 6 Coaxial cable inner conductor 7 Coaxial cable outer conductor 11 Probe casing 11A Engaging member 11B Inclined tip surface 24 Calculation / recording device 25 Rotation / Support device

Claims (2)

  A probe for electric field detection, characterized in that the inner conductor and outer conductor of a coaxial cable are exposed from the tip surface inclined with respect to the central axis.   A three-dimensional electric field is detected by detecting the electric field at the initial position, 90 degree rotation, and 180 degree rotation position by using an electric field detection probe in which the inner conductor and outer conductor of the coaxial cable are exposed from the tip surface inclined with respect to the central axis. A three-dimensional electric field measurement method characterized by measuring a current.

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