JP2003149308A - Magnetic field measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect a magnetic field ranged from dozens of Hz to hundreds of kHz. SOLUTION: The apparatus comprises a magnetic field detecting means 1 wherein at least three coils 2, 3 and 4 are arranged in a direction of three axes orthogonally crossed one another so as to have a common center point; and a CR integration means 11 having an integration characteristic with respect to integration output bands of coils 2, 3 and 4.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a magnetic field of about 100 kHz from a commercial power supply. 2. Description of the Related Art In a living environment, a transmission line, a transformer, an electromagnetic cooker or the like emits an alternating electromagnetic field having a very wide frequency band from a commercial frequency to several tens to 100 kHz in an unspecified direction. ing. Although such an electromagnetic field is weak, there is a concern about safety for a living body, and there is a demand for a device that can easily measure such an electromagnetic field. When such a magnetic field is detected by a solid-state element such as a Hall element or a magnetoresistive element, a shield member is required because the direction of the magnetic field to be detected must be defined. In particular, there is a problem that the shield structure becomes large for a low-frequency magnetic field. If the magnetic field in each direction is measured while positioning the solid state element at the same position in order to avoid such a problem, a device for holding the solid state element at a predetermined position is required, and the structure becomes complicated. There is. On the other hand, according to the magnetic field detecting means in which the wires are arranged in three directions so as to be orthogonal to each other, the magnetic field at a specific position is
Although it can be detected separately in the direction, the detection output changes more than the frequency due to the differential characteristics of the wire loop,
There is a problem that detection accuracy is low. The present invention has been made in view of such circumstances, and a purpose thereof is to provide a magnetic field capable of measuring a magnetic field of about several hundred kHz from a commercial frequency using a magnetic field detecting means using a wire loop. It is to provide a measuring device. According to the present invention, at least three wire loops are arranged so as to have a common center point in three axial directions orthogonal to each other. And a CR integrator having an integral characteristic with respect to the differential output band of the wire loop. The differential characteristic of the wire loop in the low frequency region is canceled out by the frequency effect of the CR integration means, and the electromotive force generated by the wire loop is flattened. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; FIG. 1 shows an embodiment of the present invention, and shows only a circuit configuration for one channel for simplification. The magnetic field detecting means 1 is constituted by arranging wires 2, 3, and 4 in three axial directions X, Y and Z orthogonal to each other. As shown in FIG. 2, such a magnetic field detecting means is formed by forming grooves 21, 22, 23 orthogonal to each other in a bobbin 20, and winding a wire loop in each of the grooves 21, 22, 23. Can be. Thereby, each wire loop 2, 3, 4
Can be arranged to have a common center. The signals of each of the loops 2, 3, and 4 are connected to a lead 5,
The signal is output to the amplifying means 10 having a flat gain at least with respect to the frequency to be detected via the signals 6 and 7.
The signal from the amplifying means 10 is supplied to a CR integrator 11 described later.
The signal is output to the output amplifying unit 12 via a display unit, and is used for analysis of magnetic field characteristics by a display device or a signal processing unit (not shown). The integrating means 11 includes a resistor 13 and a capacitor 1
4 and an operational amplifier 15, and the integration constant is set so that the integration characteristic is exhibited at the frequency at which the differential characteristic of each of the wires 2, 3, and 4 occurs. That is, the output voltage V1 from the wires 2, 3, and 4 is as follows: V1 = Kbnf (where K is a constant, b is a magnetic flux density, and f is an alternating frequency)
And the peak magnetic flux density b as shown in FIG.
Is constant, the output voltage V1 increases due to the differential characteristic of increasing in proportion to the alternating frequency. On the other hand, the output voltage V2 of the CR integrator is V2 = 1 / CR * ∫V0dt (where CR is an integration constant and V0 is an input voltage).
Then, as shown in FIG. 3B, the output of the integrated value of the input signal having a constant voltage decreases with the alternating frequency. In this embodiment, when the magnetic field detecting means 1 is set in the measurement area, three wire loops 2 having a common center,
A magnetic field intersects 3 and 4, and output voltages Vs1, Vs2 and Vs3 proportional to the magnetic field in each direction are output from each of the wires 2, 3, and 4. Although the values of these output voltages Vs1, Vs2, Vs3 greatly depend on the alternating frequency, the CR integrator 1
1 and is flattened by the frequency effect of the CR integrator 11. Therefore, it is possible to detect the intensity of the magnetic field of about several tens to 100 kHz near the center point of the wire loops 2, 3, and 4 without changing the position of the magnetic field detecting means 1. FIG. 4 shows the result of measuring the magnetic flux from a magnetic flux generating source in which the peak magnetic flux density is constant and the alternating frequency changes by the same magnetic field measuring apparatus. It was possible to measure at a substantially constant sensitivity without being affected by the above. As described above, according to the present invention, it is possible to detect a magnetic field in a wide frequency band at a specific position with high accuracy without requiring a special device for positioning the magnetic field detecting means. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a magnetic field measuring device according to the present invention. FIG. 2 is a view showing an embodiment of a winding frame of a wire loop constituting a magnetic field detecting means used in the above device. FIGS. 3 (a) and 3 (b) are diagrams showing frequency characteristics of a magnetic field detecting means and a frequency characteristic of a CR integrating means used in the same device, respectively. FIG. 4 is a diagram showing frequency characteristics of the above device. [Description of Signs] 1 Magnetic field detecting means 2, 3, 4 Wire loop 10 Amplifying means 11 CR integrating means 12 Output amplifying means

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kenichi Yamazaki             1646 Abiko, Abiko-shi, Chiba Electric Power Corporation             Central Research Laboratory Komae Research Laboratory F-term (reference) 2G017 AA01 AA15 AD02 BA05 BA16

Claims (1)

Claims: 1. A magnetic field detecting means in which at least three wire loops are arranged in three axial directions orthogonal to each other so as to have a common center point, and a differential output band of the wire loop is provided. And a CR integrating means having integral characteristics.