JPH0511077U - Commercial frequency uniaxial magnetic flux density meter - Google Patents

Abstract

(57) [Summary] [Purpose] To be able to measure the magnitude and direction of the magnetic field generated for each specific frequency or band. [Structure] The sensor 1 senses a magnetic field and the sensor 1 electrically converts the magnetic flux density of the magnetic field.
By passing only an electric signal in a predetermined frequency band through the filter 2 and further directly inputting the electric signal into the measuring unit 7 or extracting and inputting only the electric signal corresponding to the commercial frequency magnetic field, the commercial frequency magnetic field The magnetic flux density and the magnetic flux density of the broadband frequency magnetic field including the magnetic flux density are obtained from the effective value and the peak value of each electric signal and compared to identify the source of the influential magnetic field.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of a magnetic flux density meter. More specifically, the present invention relates to a commercial frequency uniaxial magnetic flux density meter for measuring the magnetic flux density by distinguishing between the commercial frequency magnetic field generated from an electric power facility and the other broadband frequency magnetic field.

[0002]

[Prior Art]

 In recent years, many IC devices such as LSIs and CPUs have been used for various electric devices and electronic devices. In such IC devices, commercial frequency magnetic fields (magnetic fields generated from commercial power sources) and broadband frequency magnetic fields (power sources other than commercial power sources) from electric power facilities such as power transmission and transformation facilities and electric and electronic devices such as personal computers and televisions. There is an increasing possibility that a malfunction will occur due to the influence of the magnetic field generated by the equipment and electric field.

As a countermeasure against this malfunction, it is necessary to measure the magnitude and direction of the magnetic field generated from various commercial power supply facilities, devices, etc. to identify the source and to reduce the magnetic field generated in the source. There is. Therefore, in the past, a magnetometer was used and placed near a power facility, electricity, electronic equipment, etc. that is presumed to generate a commercial frequency magnetic field or a broadband frequency magnetic field, and Corresponding by measuring the direction. This magnetometer is an indicator instrument that measures the magnetic flux by applying the principle of a moving coil shock galvanometer, and the control torque acting on the movable part is made small enough to be ignored. The vibration period is set to be extremely long, and the fluctuation is almost independent of the time required to change the magnetic flux and the resistance of the circuit.

[0004]

[Problems to be solved by the device]

 However, the conventional magnetic flux densitometer measures the presence or absence of magnetic flux and its magnitude, and cannot measure the frequency of the generated magnetic field. For this reason, the presence of a magnetic field could be detected, but it was not possible to determine whether it was generated from a commercial power source or from other power sources or devices.

An object of the present invention is to provide a commercial frequency uniaxial magnetic flux density meter that can measure a commercial frequency magnetic field and a broadband frequency magnetic field up to a predetermined band while distinguishing them easily and accurately.

[0006]

[Means for Solving the Problems]

 In order to achieve such an object, the commercial frequency uniaxial magnetic flux density meter of the present invention selects a sensor for sensing a magnetic field, and a commercial frequency magnetic field and a wideband frequency magnetic field in a predetermined band among the magnetic fields sensed by the sensor. A filter that allows the magnetic field to pass through, a measuring unit that measures the effective value and the peak value of the magnetic flux density in the commercial frequency magnetic field and the broadband frequency magnetic field of a predetermined band, and a unit that outputs the measured value to the outside. ing.

[0007]

[Action]

 Therefore, when the magnetic field interlinks with the sensor, an electric signal proportional to the strength and change of the magnetic field is generated in the sensor because the electric field and the magnetic field are in close relation to each other. Then, of these electric signals, only the electric signal corresponding to the commercial-frequency magnetic field is passed through the filter to measure its strength, while the strength of the entire measured magnetic field including the commercial-frequency magnetic field is measured to compare these. With this, it is possible to measure the magnetic flux density of the commercial frequency magnetic field generated from an electric power facility and the broadband frequency magnetic field of a predetermined band separately from the generated magnetic field.

[0008]

【Example】

 Hereinafter, the configuration of the present invention will be described in detail based on the embodiments shown in the drawings.

FIG. 1 shows an embodiment of the present invention. This commercial frequency uniaxial magnetic flux density meter includes a sensor 1 for detecting a magnetic field, a filter for passing only a specific frequency band, a sensitivity switching switch 3, an amplifier 4, and a bandpass filter 5 (hereinafter referred to as BPF). ), A band changeover switch 6, a measuring section 7 for obtaining an effective value and a peak value, a display changeover switch 8, a display section 9 for displaying a measurement result and the like, and a power supply section 10. All parts except the sensor 1 are housed in a metallic box 11 and magnetically shielded. The magnetic flux density meter of this embodiment measures the magnetic flux density in the uniaxial direction of the magnetic field strength represented by the vector amounts in the X, Y and Z axial directions.

The sensor 1 senses an external magnetic field, converts it into an electric signal, and sends it to the filter 2 in the next stage. For example, in the case of this embodiment, an air-core coil having an outer diameter of about 10 cm is adopted. Then, it is connected to the filter 2 by a connector via a cable of an appropriate length. The sensor 1 is not particularly limited to the air-core coil as in this embodiment, but may be a sensor that can detect a predetermined magnetic field and change into a predetermined electric signal, for example, a magnetic sensor such as a Hall element. ..

The filter 2 has a function of passing frequencies in a predetermined band, and in this embodiment, a 1 / f characteristic filter is used. The frequency band of the filter 2 in this embodiment is set to about 10 kHz from the commercial frequency, that is, 50 Hz (or 60 Hz), and is provided so that frequencies in other bands are cut. In Japan, 50 Hz and 60 Hz exist as commercial frequency magnetic fields, but a 60 Hz commercial frequency magnetic field can be included by adopting 50 Hz as the lower limit value of the setting band in the filter 2. Further, the upper limit value of the broadband frequency magnetic field is set to 10 kHz in this embodiment, but it goes without saying that it can be appropriately changed according to the usage mode.

The amplifier 4 amplifies the electric signal from the filter 2, and is provided so as to obtain a predetermined gain in a state where the level of the electric signal from the filter 2 is proportional to the magnetic flux density of the magnetic field. Further, a sensitivity changeover switch 3 is provided in the preceding stage of the amplifier 4, and an electric signal strength that is easy to process is obtained by operating the sensitivity changeover switch 3. For example, when the electric signal level is proportional in the magnetic flux density of the magnetic field in the range of 0.1 mG to 20 G, by switching the sensitivity changeover switch 3, 0.1 mG to 200 mG or 1 mG to 2 G or 10 mG. The electric signal proportional to the magnetic flux density range of 20 to 20 G can be obtained from the amplifier 4.

One of the measuring units 7 is directly connected to the amplifier 4 via the band changeover switch 6, and the other is connected to the amplifier 4 via the band changeover switch 6 and the BPF 5. The measuring section 7 is composed of an effective value calculating section 7a for calculating the effective value of the input electronic signal and a peak value detecting section 7b for detecting the peak value, that is, the peak value of the input electric signal. Therefore, by manually switching the band changeover switch 6, the effective value and peak value of the electric signal from 50 Hz to 10 kHz are measured, and the electric signal corresponding to the commercial frequency magnetic field (50 Hz or 60 Hz) is measured. Measure the rms value and peak value.

The BPF 5 allows only an electric signal of a predetermined frequency, for example, 50 Hz or 60 Hz to pass therethrough, and is provided so as to attenuate electric signals of other frequencies, for example, 18 dB / oct per octave. ing. Therefore, the attenuation is 18 dB for an electric signal having a frequency twice or half the commercial frequency. The bandpass value of the BPF 5 is changed according to two types of commercial frequencies of 50 Hz and 60 Hz.

An external AC monitor output terminal 7C is attached to the measuring unit 7 so that an electric signal can be monitored by an oscilloscope, a recorder, a storage scope, or the like.

The display unit 9 is connected to the measuring unit 7 via the display changeover switch 8, and the display changeover switch 8 switches the display of the effective value of the magnetic flux density of the measurement frequency magnetic field and the peak value. To do. By switching the band change switch 6 and the display change switch 8, the effective value and the peak value of the electric signal corresponding to the broadband frequency magnetic field of 50 Hz to 10 kHz and the electric signal corresponding to the commercial frequency magnetic field are respectively displayed. Can be done. Further, in the present embodiment, the LCD is used for the display unit 9 in consideration of power consumption and the like, but it is not particularly limited to this, and other display means such as plasma LED may be used. It is possible.

The display unit 9 is provided with a pen output terminal 9a, and the effective value and the peak value of the electric signal proportional to each frequency magnetic field measured by the measuring unit 7 are recorded by an external recording means. It is configured to be able to. The power supply unit 10 supplies a DC voltage or the like required for the internal device. In the case of this embodiment, the magnetic flux density meter is composed of a battery 10a and a dedicated AC adapter in order to make it simple and portable. ing . However, if AC power can always be obtained, a switching regulator or a series regulator type DC power supply may be incorporated inside.

Next, the measurement operation in this example will be described. The external magnetic field sensed by the sensor 1 is converted by the sensor 1 into an electric signal, for example, a voltage signal in the case of this embodiment, and then sent to the filter 2 of the next stage. Then, the frequency components from 50 Hz to 10 kHz set by the 1 / f characteristic filter 2 pass through the filter 2 and are sent to the amplifier 4. In this state, the magnetic flux density of the magnetic field is proportional to the voltage signal. Then, this voltage signal is amplified by the amplifier 4 by the gain set by the sensing changeover switch 3 and input to the measuring unit 7. At this time, the voltage signal has a path that is directly input to the measuring unit 7 via the band changeover switch 6 and a path that is input via the BPF 5 and the band changeover switch 6, and the measurer may use it as necessary. The band changing switch 6 is changed. That is, when it is desired to measure the magnetic flux density of the broadband frequency magnetic field from the commercial frequency magnetic field (50 Hz) to 10 kHz, the magnetic flux density of the commercial frequency magnetic field (50 Hz) is switched to the side directly connected to the amplifier 4. If you want to measure the density, switch to the side connected to BPF5. When all the electric signals from the amplifier 4 are input to the measuring unit 7, the effective value of the magnetic flux density of the entire broadband frequency magnetic field and the peak value are calculated and displayed on the display unit 9. When the electric signal from the amplifier 4 is passed through the BPF 5 and input to the measuring unit 7, the effective value and the peak value of only the commercial frequency magnetic field are calculated and displayed on the display unit 9.

It is known that the following relationship is established between the effective value and the peak value. That is, when the voltage is a sine wave, the peak value = √2 × effective value. Therefore, if the source of the magnetic field emits only a sinusoidal magnetic field (in this case, the commercial frequency magnetic field of 50 Hz and 60 Hz) or if the sinusoidal magnetic field is the main component, the effective value obtained by the measuring unit 7 And the crest value becomes the value that satisfies the relation of the above equation. Therefore, it can be estimated that the magnetic field of the generation source when this relationship holds is a sine wave, and thus a commercial frequency magnetic field. On the other hand, if the measured values of the 50 Hz (or 60 Hz) magnetic field and the broadband magnetic field measured by switching the band selector switch 6 are different, a harmonic of the commercial frequency or a magnetic field of a high frequency unrelated to the commercial frequency is generated. It means that they are doing. For example, if the detected magnetic field is large when the band selector switch 6 is switched to the wide band side, it can be seen that the magnetic field at frequencies other than the commercial frequency is strong. Then, when the effective value and the peak value of the magnetic field from the magnetic field source containing a high-harmonic component other than a sine wave (components up to 10 kHz can be measured by this measuring instrument) are measured, It does not hold, and the higher the crest value is more than √2 times the effective value, the sharper the waveform becomes. In the opposite case, it can be inferred that the waveform becomes gentler.

Therefore, the waveform of the magnetic field can be roughly estimated by switching the two switches of the band changeover switch 6 and the display changeover switch 8. That is, by measuring and comparing the magnetic flux density of the commercial frequency magnetic field and the magnetic flux density of the broadband frequency magnetic field up to a certain frequency including this commercial frequency magnetic field, the measured values of the commercial frequency magnetic field and the broadband frequency magnetic field are different. For example, it is possible to determine that a harmonic of the commercial frequency or a magnetic field of a high frequency unrelated to the commercial frequency is generated, and it is possible to determine whether the commercial frequency magnetic field or another generated magnetic field has a greater effect. Then, by determining the relationship between the effective value and the crest value, it is possible to estimate whether or not the generated magnetic field is a sine wave and what kind of waveform it is, and to specify the source. For example, it is clear that when the magnetic field is measured under the power transmission line, only the commercial frequency component is contained, and when the magnetic field leaking from a television or the like is measured, components other than the commercial frequency are included. If the commercial frequency magnetic field is large even if it contains components other than the commercial frequency, the source can be specified by directing the sensor to each commercial power source and measuring only the commercial frequency magnetic field. The effective value and the peak value are displayed on the LCD of the display unit 9 by appropriately switching the display changeover switch 8.

[0021]

[Effect of the device]

 As is clear from the above description, the commercial frequency uniaxial magnetic flux density meter of the present invention can measure the crest value (peak value) and the effective value of the magnetic flux density of the commercial frequency magnetic field and the magnetic flux density of the broadband frequency magnetic field. , The magnetic field generated from electric and electronic equipment with waveform distortion and the magnetic field generated from commercial frequency sources such as power facilities can be measured separately, and the location of noise and waveform distortion in the measurement environment can be easily estimated. can do. Further, the configuration itself is very simple and can be downsized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a commercial frequency uniaxial magnetic flux density meter of the present invention.

[Explanation of symbols]

 1 Sensor 2 Filter 5 Bandpass Filter 6 Band Selector Switch 7 Measuring Section 9 Display Section

Claims (1)

Claims for utility model registration: 1. A sensor for sensing a magnetic field, and a filter for selectively passing a commercial frequency magnetic field and a broadband frequency magnetic field of a predetermined band among the magnetic fields sensed by the sensor.
A commercial frequency single axis having a measuring device section for measuring the effective value and the peak value of the magnetic flux density in the commercial frequency magnetic field and the broadband frequency magnetic field of a predetermined band, and means for outputting the measured value to the outside. Magnetic flux density meter.