Demagnetizer and demagnetizer mode switching device

Abstract

The present invention provides a demagnetizing device that can reduce noise superimposed on the demagnetizing current without using a large transformer, and a demagnetizing mode switching device for such a demagnetizing device. [Solution] The demagnetizing device 1 is a demagnetizing device 1 that reduces the residual magnetic field of a magnetic shielding device 5 equipped with magnetic shielding members 51, 52 that shield from external magnetic fields, and comprises a demagnetizing unit 30 connected to a power supply 40 that supplies a damped sinusoidal current or a damped triangular current and disposed relative to the magnetic shielding member, and a demagnetizing mode switching means 10 that switches the magnitude of the damped sinusoidal current or a damped triangular current flowing through the demagnetizing unit 30.

Description

[Technical Field]

[0001] The present invention relates to a degaussing device for reducing residual magnetic field in a magnetic shield device provided with a magnetic shield member that shields magnetism from the outside, and to a degaussing mode switching device for such a degaussing device. [Background Art]

[0002] Conventionally, in biomagnetic measurement using a high-sensitivity magnetic sensor represented by magnetoencephalography, a magnetic shield device such as that disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-311523) has been used to shield magnetism from the outside. Furthermore, in recent years, along with the demand for higher performance of magnetic sensors and improvement in measurement accuracy, a lower magnetic field environment than ever before is required, and it is required that the residual magnetic field in the magnetic shield device be kept below a certain value. To address this, in order to reduce residual magnetic field, for example, as disclosed in Patent Document 2 (Japanese Patent Publication No. 58-014053), a low magnetic field is obtained (degaussing) by temporarily applying a temporally decaying magnetic field to a magnetic shield wall. Furthermore, there is current noise derived from a power source that is superimposed on the current that applies the degaussing magnetic field. An example is disclosed in which a transformer is inserted immediately before a degaussing magnetic field application coil to reduce this noise [e.g., Non-Patent Document 1 (REVIEW OF SCIENTIFIC INSTRUMENTS 78, 035106 (2017))]. It is shown that slight noise is superimposed on the power source that drives the coil, and this noise is reflected in the residual magnetic field after degaussing. It is disclosed that since the pass frequency band of the transformer is narrow, the residual magnetic field in the final magnetic shield room can be made extremely small by reducing the current noise superimposed on the degaussing current. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Laid-Open No. 2007-311523 [Patent Document 2] Special Public Notice No. 58-014053 [Non-patent literature]

[0004] [Non-Patent Document 1] REVIEW OF SCIENTIFIC INSTRUMENTS 78,035106(2017) [Overview of the project] [Problems that the invention aims to solve]

[0005] Here, the present inventors conceived of a problem concerning a demagnetizing device using a transformer, as shown in Non-Patent Document 1. In other words, the inventors have found that demagnetization can be performed more efficiently with a current at a lower frequency (e.g., a few Hz) than the commercial frequency of 50 Hz or 60 Hz, and Non-Patent Literature 1 also shows that residual magnetic fields can be reduced by inserting a transformer with a passband centered on 10 Hz, which is lower than the commercial frequency. However, the current flowing through the demagnetizing coil is a large current of several amperes to about 10 amperes, and even a transformer with a passband of the commercial frequency is quite large (e.g., 10 kg or more). A transformer with a passband of low frequencies (a few Hz) without saturating the iron core of the transformer would be even larger (e.g., several hundred kg or more), and a demagnetizing device equipped with such a transformer would lack practicality. Therefore, there is a problem that noise reduction by inserting a transformer is not suitable for demagnetizing devices to be realized for commercial use. Therefore, the object of the present invention is to provide a demagnetizing device for reducing the residual magnetic field of a magnetic shielding device equipped with a magnetic shielding member for shielding from external magnetic fields, and a demagnetizing mode switching device for such a demagnetizing device, which can reduce noise superimposed on the demagnetizing current without using a large transformer, and a demagnetizing mode switching device for such a demagnetizing device. [Means for solving the problem]

[0006] The following will achieve the above objectives: (1) A demagnetizing device for reducing the residual magnetic field of a magnetic shielding device equipped with a magnetic shielding member that shields from external magnetic fields, A demagnetizing unit is connected to a power supply that provides a damped sinusoidal current or a damped triangular wave current, and is disposed relative to the magnetic shielding member, A demagnetization mode switching means for switching the magnitude of the attenuated sinusoidal current or attenuated triangular wave current flowing through the demagnetization section, A demagnetizing device equipped with the following features.

[0007] Furthermore, the following items will achieve the above objectives. (2) A demagnetizing device for reducing the residual magnetic field of a magnetic shielding device equipped with a magnetic shielding member that shields from external magnetic fields, A power supply that provides a damped sinusoidal current or a damped triangular wave current, A demagnetizing unit connected to the power supply and disposed relative to the magnetic shielding member, A demagnetization mode switching means, located outside the power supply, which switches the magnitude of the attenuated sinusoidal current or attenuated triangular wave current flowing through the demagnetization section, A demagnetizing device equipped with the following features.

[0008] (3) The demagnetization mode switching means comprises a resistor connected in parallel with the demagnetization unit, and a switching unit that switches whether or not there is continuity between the power supply and the resistor, The resistor has a resistance value smaller than that of the demagnetizing section. The demagnetizing device according to (1) or (2) above, which is capable of switching between a high-current demagnetizing mode in which the resistor is not conductive and a low-current demagnetizing mode in which the resistor is conductive. (4) The demagnetizing device according to (3) above, wherein the resistance value of the resistor is 1 / 3 or less of the resistance value of the demagnetizing section. (5) The demagnetization mode switching means comprises a first resistor connected in series with the demagnetization unit, a second resistor connected in parallel with the demagnetization unit and the first resistor, and a switching unit that switches whether or not there is continuity between the power supply and the second resistor. The second resistor has a resistance value smaller than the sum of the resistance value of the first resistor and the resistance value of the demagnetizing section. The demagnetizing device according to (1) or (2) above, which is capable of switching between a high-current demagnetizing mode in which the second resistor is not connected and a low-current demagnetizing mode in which the second resistor is connected. (6) The demagnetizing device according to (5) above, wherein the resistance value of the second resistor is 1 / 3 or less of the sum of the resistance value of the first resistor and the resistance value of the demagnetizing unit. (7) The demagnetization mode switching means comprises a first resistor that can be connected in series with the demagnetization unit, a second resistor that can be connected in series with the demagnetization unit and has a greater resistance value than the first resistor, and a switching unit that switches the connection between the power supply and the first resistor or the second resistor. The demagnetizing device according to (1) or (2) above, which is capable of switching between a high-current demagnetizing mode when connected to the first resistor and a low-current demagnetizing mode when connected to the second resistor. (8) The demagnetizing device comprises a first power supply that supplies a damped sinusoidal current or a damped triangular current, and a second power supply that supplies a damped sinusoidal current or a damped triangular current smaller than that of the first power supply, The demagnetizing device according to (1) or (2) above, wherein the demagnetizing mode switching means is capable of switching between a high-current demagnetizing mode using the first power supply and a low-current demagnetizing mode using the second power supply. (9) The demagnetizing device according to any one of (1) to (8) above, wherein the magnetic shielding device comprises two or more layers of magnetic shielding members, and the demagnetizing unit is disposed relative to the innermost layer of the magnetic shielding member.

[0009] Furthermore, the following items will achieve the above objectives. (10) A demagnetization mode switching device for a demagnetization device comprising: a power supply that supplies a damped sinusoidal current or a damped triangular current to reduce the residual magnetic field of a magnetic shielding device equipped with a magnetic shielding member that shields from external magnetic fields; and a demagnetization unit connected to the power supply and disposed relative to the magnetic shielding member, Said demagnetization mode switching device comprises demagnetization mode switching means for switching the magnitude of the attenuated sine wave current or attenuated triangular wave current flowing through said demagnetization unit, Said demagnetization mode switching means comprises a first resistor connected in series with said demagnetization unit, a second resistor connected in parallel with said demagnetization unit and said first resistor, and a switching unit for switching whether conduction between said power source and said second resistor is established or not, A demagnetization mode switching device capable of switching between a large-current demagnetization mode in which said second resistor is not brought into conduction and a small-current demagnetization mode in which said second resistor is brought into conduction.

[0010] (11) The demagnetization mode switching device according to (10) above, wherein said second resistor has a resistance value smaller than the sum of the resistance value of said first resistor and the resistance value of said demagnetization unit. (12) The demagnetization mode switching device according to (10) above, wherein the resistance value of said second resistor is 1 / 3 or less of the sum of the resistance value of said first resistor and the resistance value of said demagnetization unit. Effects of the Invention

[0011] The demagnetization device of the present invention is a demagnetization device for reducing the residual magnetic field of a magnetic shield device including a magnetic shield member that shields magnetism from the outside, the demagnetization device comprising: a demagnetization unit connected to a power supply that supplies an attenuated sine wave current or an attenuated triangular wave current and disposed opposite to said magnetic shield member; and demagnetization mode switching means for switching the magnitude of the attenuated sine wave current or attenuated triangular wave current flowing through said demagnetization unit. Thereby, noise superimposed on the demagnetization current can be reduced without using a large transformer.

[0012] Further, the demagnetization device of the present invention is a demagnetization device for reducing the residual magnetic field of a magnetic shield device including a magnetic shield member that shields magnetism from the outside, the demagnetization device comprising: a power supply that supplies an attenuated sine wave current or an attenuated triangular wave current; a demagnetization unit connected to said power supply and disposed opposite to said magnetic shield member; and demagnetization mode switching means disposed outside said power supply for switching the magnitude of the attenuated sine wave current or attenuated triangular wave current flowing through said demagnetization unit. Accordingly, noise superimposed on the degaussing current can be reduced without using a large transformer.

[0013] Further, the degaussing mode switching device of the present invention is a degaussing mode switching device for a degaussing device, comprising: a power supply that supplies damped sine wave current or damped triangular wave current for reducing a residual magnetic field of a magnetic shield device including a magnetic shield member that shields magnetism from the outside; and a degaussing unit connected to the power supply and disposed facing the magnetic shield member, wherein the degaussing mode switching device comprises degaussing mode switching means for switching the magnitude of the damped sine wave current or damped triangular wave current flowing through the degaussing unit, the degaussing mode switching means comprises a first resistor connected in series with the degaussing unit, a second resistor connected in parallel with the degaussing unit and the first resistor, and a switching unit that switches whether conduction between the power supply and the second resistor is enabled or disabled, and the degaussing mode switching device is capable of switching between a large current degaussing mode in which the second resistor is not conducted and a small current degaussing mode in which the second resistor is conducted. Accordingly, noise superimposed on the degaussing current can be reduced without using a large transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] [Figure 1] Figure 1 is a perspective explanatory view showing an example of a magnetic shield device in which the degaussing device of the present invention is used. [Figure 2] Figure 2 is a schematic cross-sectional explanatory view showing an example of a magnetic shield device in which the degaussing device of the present invention is used. [Figure 3] Figure 3 is a schematic explanatory view showing an embodiment of the degaussing device of the present invention. [Figure 4] Figure 4 is a schematic explanatory view showing one step of a degaussing operation performed by the degaussing device shown in Figure 3. [Figure 5] Figure 5 is a schematic explanatory view showing another embodiment of the degaussing device of the present invention. [Figure 6] Figure 6 is a schematic explanatory view showing one step of a degaussing operation performed by the degaussing device shown in Figure 5. [Figure 7]Figure 7 is a schematic diagram illustrating one step of the demagnetization operation using the demagnetization device shown in Figure 5. [Figure 8] Figure 8 is a schematic diagram illustrating another embodiment of the demagnetizing device of the present invention. [Figure 9] Figure 9 is a schematic diagram illustrating one step of the demagnetization operation using the demagnetizing device shown in Figure 8. [Figure 10] Figure 10 is a schematic diagram illustrating another embodiment of the demagnetizing device of the present invention. [Figure 11] Figure 11 is a schematic diagram illustrating one step of the demagnetization operation using the demagnetization device shown in Figure 10. [Figure 12] Figure 12 is a schematic diagram illustrating one step of the demagnetization operation using the demagnetization device shown in Figure 10. [Figure 13] Figure 13 is a schematic diagram illustrating another embodiment of the demagnetizing device of the present invention. [Figure 14] Figure 14 is a schematic diagram illustrating one step of the demagnetization operation using the demagnetizing device shown in Figure 13. [Figure 15] Figure 15 is a schematic diagram illustrating one step of the demagnetization operation using the demagnetizing device shown in Figure 13. [Figure 16] Figure 16 is a schematic diagram illustrating an embodiment of the demagnetization mode switching device of the present invention. [Figure 17] Figure 17 is a schematic diagram illustrating one step of the demagnetization operation using the demagnetization mode switching device shown in Figure 16. [Figure 18] Figure 18 is a schematic diagram illustrating the magnitude of the demagnetizing current and the magnitude of the noise current superimposed on the demagnetizing current during demagnetization operation using the demagnetizing device and demagnetizing mode switching device of the present invention. [Modes for carrying out the invention]

[0015] The demagnetizing device and demagnetizing mode switching device of the present invention will be described using the embodiments shown in the drawings. As shown in Figures 1 to 4, the demagnetizing device 1 of the present invention is a demagnetizing device 1 for reducing the residual magnetic field of a magnetic shielding device 5 equipped with magnetic shielding members 51 and 52 that shield from external magnetic fields, and comprises a demagnetizing unit 30 connected to a power supply 40 that supplies a damped sinusoidal current or a damped triangular wave current and disposed relative to the magnetic shielding member, and a demagnetizing mode switching means 10 for switching the magnitude of the damped sinusoidal current or a damped triangular wave current flowing through the demagnetizing unit 30.

[0016] Furthermore, the demagnetizing device of the present invention is a demagnetizing device for reducing the residual magnetic field of a magnetic shielding device 5 equipped with magnetic shielding members 51 and 52 that shield from external magnetic fields, and may include a power supply 40 that supplies a damped sinusoidal current or a damped triangular current, a demagnetizing unit 30 connected to the power supply 40 and disposed relative to the magnetic shielding member, and a demagnetizing mode switching means 10 disposed outside the power supply 40 (between the power supply 40 and the demagnetizing unit 30) that switches the magnitude of the damped sinusoidal current or damped triangular current flowing through the demagnetizing unit 30.

[0017] Here, an example of a magnetic shielding device in which the demagnetizing device of the present invention is used will be described. As shown in Figures 1 and 2, the magnetic shielding device 5 of this embodiment is a magnetic shielding device 5 that comprises two or more layers of magnetic shielding members (here, two layers of magnetic shielding members 51, 52) to shield from external magnetism, and is capable of housing a magnetic sensor (not shown) and a test subject (not shown) inside.

[0018] The magnetic shielding device 5 is for shielding (reducing or blocking) external magnetic fields. In this embodiment, the magnetic shielding device 5 comprises a box-shaped device body 50, and a magnetic shielding space 53 is formed inside the device body 50 (inside the innermost magnetic shielding member 51). Although not described in detail, as shown in Figure 1, the device body 50 of the magnetic shielding device 5 is provided with an entrance / exit for entering and exiting the magnetic shielding space 53, and a door 54 that can open and close the entrance / exit. Measuring jigs, etc. (not shown) may be installed in the magnetic shielding space 53. The magnetic shielding device 5 may also be equipped with a function (device) for maintaining a constant temperature in the magnetic shielding space 53.

[0019] The magnetic shielding device 5 comprises two or more layers of magnetic shielding members. Specifically, the main body 50 of the magnetic shielding device 5 in this embodiment comprises two layers of magnetic shielding members 51 and 52, an innermost magnetic shielding member (a box-shaped innermost shield wall portion composed of the innermost magnetic shielding member) 51 that defines the magnetic shielding space 53, and an outer magnetic shielding member (a box-shaped outer shield wall portion composed of the outer magnetic shielding member) 52 that surrounds the innermost magnetic shielding member 51 and is adjacent to the innermost magnetic shielding member 51 at a predetermined distance to the outside. Although not described in detail, it is preferable that each magnetic shielding member (innermost shield wall portion and outer shield wall portion) 51 and 52 is configured to have as few gaps as possible in order to prevent the intrusion of magnetism. Furthermore, each magnetic shielding member (innermost shield wall portion and outer shield wall portion) 51, 52 is preferably structured with as few openings as possible, but openings may be provided as needed (for example, for drawing in various measuring cables, etc.).

[0020] In this embodiment, each magnetic shielding member 51, 52 is composed of a plate-shaped member formed from a high-permeability material. Examples of materials that constitute such magnetic shielding members 51, 52 include iron and permalloy, with permalloy having a relatively high nickel content (e.g., permalloy C) being particularly preferred. Permalloy is a high-permeability metallic material mainly composed of nickel and iron, with a nickel content of 35-80%. In the magnetic shielding device 5 of this embodiment, it is preferable that the permalloy constituting the magnetic shielding members 51, 52 has a nickel content of 75-82%. Furthermore, the thickness of the magnetic shielding members 51, 52 (the thickness of the plate-shaped member constituting the magnetic shielding members 51, 52) is preferably 1-2 mm.

[0021] In this embodiment, the magnetic shielding device 5 is equipped with two layers of magnetic shielding members 51 and 52. However, the number of layers of magnetic shielding members in the magnetic shielding device may be increased depending on the surrounding magnetic environment. For example, it is preferable that the number of layers of magnetic shielding members in the magnetic shielding device be 3 to 4.

[0022] Furthermore, although not described in detail here, it is preferable that the innermost magnetic shielding member 51 is supported by the bottom wall portion of the outer magnetic shielding member 52 via a base 55, and that there are no supports such as pillars that support the lateral direction or the ceiling surface. It is also preferable that the innermost magnetic shielding member 51 is supported in a state that is vibrationally insulated from the outer magnetic shielding member 52 (a state in which vibrations from the outside or the outer magnetic shielding member 52 are less likely to be transmitted).

[0023] The demagnetizer 1 of this embodiment is connected to a power supply 40, which will be described later, and includes a demagnetizing unit 30 that is disposed relative to a magnetic shielding member (here, a magnetic shielding member 51). As described above, the magnetic shielding device 5 of this embodiment includes two or more layers of magnetic shielding members 51, 52, and the demagnetizing unit 30 is disposed relative to the innermost magnetic shielding member 51. Specifically, as shown in Figure 2, the demagnetizing unit 30 of this embodiment is a demagnetizing cable (coil) disposed near the innermost magnetic shielding member 51 through openings 56 formed in each of the magnetic shielding members 51, 52 of the magnetic shielding device 5. Note that Figure 2 is a schematic representation of the demagnetizing unit 30 and does not limit the configuration of the demagnetizing unit.

[0024] "Demagnetization" refers to an operation (demagnetization operation) that reduces the residual magnetic field of a target member (in this case, the magnetic shield member 51) by supplying current to the demagnetization unit 30 to temporarily apply a magnetic field (electrical alternating magnetic field, a magnetic field that decays over time) that is intentionally generated. In this embodiment, the demagnetizer 1 is designed so that the residual magnetic field of the innermost magnetic shield member 51 (i.e., inside the magnetic shield device 5) can be reduced by a predetermined demagnetization operation.

[0025] The power supply 40 connected to the demagnetizing unit 30 described above is a power supply capable of supplying a damped sinusoidal current or a damped triangular wave current. As such a power supply capable of supplying a damped sinusoidal current or a damped triangular wave current, known products such as the BP4610 bipolar power supply manufactured by NF Circuit Design Block Co., Ltd. can be used.

[0026] In this embodiment, the power supply 40 is a constant current power supply, and the magnitude of the attenuated sinusoidal current or attenuated triangular wave current supplied by the power supply 40 is preferably 1A to 10A, and the frequency is preferably 0.1Hz to 10Hz.

[0027] The demagnetizer 1 includes a demagnetization mode switching means 10 that switches the magnitude of the attenuated sinusoidal current or attenuated triangular wave current (including noise current) flowing through the demagnetization unit 30 (in other words, switches the magnitude of the noise current included in the current flowing through the demagnetization unit 30).

[0028] Specifically, in this embodiment, the demagnetization mode switching means 10 includes a first resistor 11 (resistance value: Rl) connected in series with the demagnetization unit 30, a second resistor 12 (resistance value: Rs) connected in parallel with the demagnetization unit 30 and the first resistor 11, and a switching unit (switch) 13 for switching between continuity between the power supply 40 and the second resistor 12. The second resistor 12 has a resistance value (Rs) smaller than the sum of the resistance value (Rl) of the first resistor 11 and the resistance value (internal resistance of the demagnetization unit 30: Ri) (Rl + Ri), and is capable of switching between a high-current demagnetization mode in which the second resistor 12 is not connected and a low-current demagnetization mode in which the second resistor 12 is connected. Note that the magnitude (maximum value) of the current flowing through the demagnetization unit 30 in the low-current demagnetization mode is smaller than the magnitude (maximum value) of the current flowing through the demagnetization unit 30 in the high-current demagnetization mode. In other words, the demagnetizer 1 (demagnetization mode switching means 10) of this embodiment can switch between a high-current demagnetization mode in which the power supply 40 is not connected to the second resistor 12 and a large current is supplied to the demagnetization unit 30 and the first resistor 11, and a low-current demagnetization mode in which the power supply 40 is connected to the second resistor 12 and a current smaller than the high current supplied to the demagnetization unit 30 and the first resistor 11.

[0029] Furthermore, the resistance value (Rs) of the second resistor 12 is preferably 1 / 3 or less of the sum of the resistance value (Rl) of the first resistor 11 and the resistance value (Ri) of the demagnetizing unit 30 (internal resistance of the demagnetizing unit 30), and more preferably 1 / 10 or less. This makes it possible to sufficiently reduce the influence of power supply-derived noise on the demagnetizing unit 30, as will be described later.

[0030] The operation for demagnetizing the magnetic shielding device 5 using the demagnetizing device 1 of this embodiment will be described below. Prior to performing the demagnetization operation, the demagnetizer 1 is connected to the prepared power supply 40, as shown in Figure 3. In Figure 3, reference numeral 14 indicates the connection point between the demagnetizer 1 and the power supply 40.

[0031] Using the demagnetizer 1, demagnetization is first performed using a high-current demagnetization mode in which the second resistor 12 is not connected. Specifically, as shown in Figure 3, the switching unit (switch) 13 is used to disconnect the power supply 40 from the second resistor 12, and a damped sinusoidal current or damped triangular wave current is supplied from the power supply 40 to the demagnetizer 30. In this high-current demagnetization mode, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped (see "High-Current Demagnetization Mode" in Figure 18; the same applies hereafter in this specification).

[0032] Next, the second resistor 12 is connected, and demagnetization is performed using a low-current demagnetization mode, which reduces the current in the demagnetization unit 30 to less than that in the high-current demagnetization mode described above. Specifically, as shown in Figure 4, in the switching unit (switch) 13, with the power supply 40 and the second resistor 12 connected, a damped sinusoidal current or damped triangular wave current is supplied from the power supply 40 to the demagnetization unit 30. It is preferable that the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 in the low-current demagnetization mode is the same current (a current with the same magnitude, frequency, damping ratio, etc.) as the high-current demagnetization mode performed prior to the low-current demagnetization mode. In the low-current demagnetization mode as well, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped (see "Low-Current Demagnetization Mode" in Figure 18; the same applies hereinafter in this specification).

[0033] The demagnetizer 1 of this embodiment divides the demagnetization operation into at least two stages: demagnetization with a large current (large current demagnetization mode) and demagnetization with a small current (small current demagnetization mode). In the first stage (large current demagnetization mode), the power supply 40 is directly connected to the demagnetization unit 30. In the second stage (small current demagnetization mode), the second resistor 12 is connected in parallel with the demagnetization unit 30 via the switching unit (switch) 13, thereby dividing the current supplied from the power supply 40 and enabling demagnetization with low noise in the demagnetization unit 30 (see the magnitude of the "noise current superimposed on the demagnetization current" in Figure 18 (vertical width of the hatched area in Figure 18). The same applies hereafter in this specification). In other words, in the second stage (low-current demagnetization mode), by dividing the current supplied from the power supply 40 and gradually reducing the current supplied from the power supply 40 (to a damped sinusoidal current or a damped triangular wave current), it is possible to reduce the influence of power supply-derived noise, which causes instability of the residual magnetic field, on the demagnetization unit 30. Furthermore, in such a demagnetizing device 1, noise superimposed on the demagnetizing current can be reduced in a practical (relatively small and inexpensive) manner using existing resistors and switches, without the need for a large transformer.

[0034] Furthermore, the power supply-derived noise that is the focus of this invention is mainly generated by the amplifier built into the power supply 40. Therefore, even if the output (in this case, the magnitude of the current) on the power supply 40 side is reduced, the magnitude of the noise does not change significantly. For this reason, the demagnetizer 1 of this embodiment functions effectively.

[0035] Furthermore, the magnitude of the above effect (the effect of reducing the influence of power supply-derived noise on the demagnetizing unit 30) can also be estimated from the theoretical formula. The influence of noise (superimposed noise current) in the attenuated sinusoidal current or attenuated triangular current supplied by power supply 40 depends on the nature and time (time from the start of current supply) of the current. However, in the following comparison, we assume that the comparison is under the same nature and time, and we will estimate by ignoring (canceling out) the influence of those parameters. Under the above assumptions, let "in" be the magnitude of the noise (superimposed noise current) in the high-current demagnetization mode. In contrast, the magnitude of the noise (superimposed noise current) in the low-current demagnetization mode is "in × [Rs / (Rs+Rl+Ri)]". Therefore, if we set the resistance values ​​to, for example, Ri=1Ω, Rs=1Ω, and Rl=10Ω, it can be inferred that in the low-current demagnetization mode, the influence of power supply-derived noise on the demagnetization unit 30 can be reduced to 1 / 12 compared to the high-current demagnetization mode.

[0036] The demagnetizing device may be a demagnetizing device 1a as shown in Figures 5 to 7. Specifically, in this embodiment, the demagnetization mode switching means 10a includes a first resistor 11 (resistance value: Rl) connected in series with the demagnetization unit 30, a second resistor 12 (resistance value: Rs) and a third resistor 15 (resistance value: Rsa) connected in parallel with the demagnetization unit 30 and the first resistor 11, a first switching unit (switch) 13 for switching the presence or absence of continuity between the power supply 40 and the second resistor 12, and a second switching unit (switch) 16 for switching the presence or absence of continuity between the power supply 40 and the third resistor 15. Preferably, the second resistor 12 has a resistance value (Rs) smaller than the sum of the resistance value (Rl) of the first resistor 11 and the resistance value (Ri) of the demagnetization unit 30 (internal resistance of the demagnetization unit 30) (Rl + Ri), and preferably the resistance value (Rsa) of the third resistor 15 is smaller than the resistance value (Rs) of the second resistor 12.

[0037] When using such a demagnetizing device 1a, demagnetization is first performed using a high-current demagnetizing mode in which the second resistor 12 and the third resistor 15 are not connected. Specifically, as shown in Figure 5, the first switching unit (switch) 13 and the second switching unit (switch) 16 are used to disconnect the power supply 40 from the second resistor 12 and the third resistor 15, and a damped sinusoidal current or damped triangular wave current is supplied from the power supply 40 to the demagnetizing unit 30. In this high-current demagnetizing mode, the demagnetizing operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped.

[0038] Next, the second resistor 12 is connected, and demagnetization is performed using a low-current demagnetization mode, which reduces the current in the demagnetization unit 30 to less than that in the high-current demagnetization mode described above. Specifically, as shown in Figure 6, in the first switching unit (switch) 13, with the power supply 40 and the second resistor 12 connected, a damped sinusoidal current or a damped triangular wave current is supplied from the power supply 40 to the demagnetization unit 30. It is preferable that the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 in the low-current demagnetization mode is the same current (a current with the same magnitude, frequency, damping ratio, etc.) as the high-current demagnetization mode performed prior to the low-current demagnetization mode. In the low-current demagnetization mode as well, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped.

[0039] Next, in this embodiment, demagnetization is performed using an extremely low-current demagnetization mode, in which the current in the demagnetization unit 30 is made even smaller than in the low-current demagnetization mode described above, by not conducting through the second resistor 12 and conducting through the third resistor 15. Specifically, as shown in Figure 7, in the first switching unit (switch) 13, the power supply 40 and the second resistor 12 are kept apart, and in the second switching unit (switch) 16, the power supply 40 and the third resistor 15 are made apart, and a damped sinusoidal current or damped triangular wave current is supplied from the power supply 40 to the demagnetization unit 30. It is preferable that the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 in the extremely low-current demagnetization mode is the same current (a current with the same magnitude, frequency, damping ratio, etc.) as the high-current demagnetization mode and low-current demagnetization mode performed prior to the extremely low-current demagnetization mode. Even in the extremely low-current demagnetization mode, the demagnetization operation continues until the attenuated sinusoidal current or attenuated triangular wave current supplied from the power supply 40 is sufficiently attenuated.

[0040] In the demagnetizer 1a of this embodiment, in the low-current demagnetization mode and the extremely low-current demagnetization mode, the current supplied from the power supply 40 is divided and the current supplied from the power supply 40 is gradually reduced (to a damped sinusoidal current or a damped triangular wave current), thereby reducing the influence of power supply-derived noise, which causes instability of the residual magnetic field, on the demagnetization unit 30.

[0041] Furthermore, even in such a demagnetizer 1a, under the assumptions described above, the magnitude of the effect of reducing the influence of power supply-derived noise on the demagnetization unit 30 can be estimated from a theoretical formula. For example, if the magnitude of the noise (superimposed noise current) in the high-current demagnetization mode is "ina", and the resistance values ​​are Ri=1Ω, Rs=1Ω, Rsa=0.1Ω, and Rl=10Ω, then the magnitude of the noise (superimposed noise current) in the low-current demagnetization mode is "ina × [Rs / (Rs+Rl+Ri)]". Therefore, it can be estimated that in the low-current demagnetization mode, the influence of power supply-derived noise on the demagnetization unit 30 can be reduced to 1 / 12 compared to the high-current demagnetization mode. Moreover, the magnitude of the noise (superimposed noise current) in the extremely low-current demagnetization mode is "ina × [Rsa / (Rsa+Rl+Ri)]", and therefore, it can be estimated that in the extremely low-current demagnetization mode, the influence of power supply-derived noise on the demagnetization unit 30 can be reduced to 1 / 111 compared to the high-current demagnetization mode.

[0042] Next, another embodiment of the demagnetizing device of the present invention will be described using the example shown in the drawings. In the following description, components that are substantially the same as those in the demagnetizing device 1 described above will be given corresponding names and reference numerals, and detailed explanations will be omitted.

[0043] As shown in Figures 8 and 9, in the demagnetizer 1b of this embodiment, the demagnetization mode switching means 10b includes a resistor 17 (resistance value: Rsb) connected in parallel with the demagnetization unit 30, and a switching unit (switch) 18 that switches between having continuity between the power supply 40 and the resistor 17. The resistor 17 has a resistance value (Rsb) smaller than the internal resistance of the demagnetization unit 30 (resistance value: Ri), and is capable of switching between a high-current demagnetization mode in which the resistor 17 is not connected and a low-current demagnetization mode in which the resistor 17 is connected. In other words, the demagnetizer 1b (demagnetization mode switching means 10b) of this embodiment is capable of switching between a high-current demagnetization mode in which the power supply 40 is not connected to the resistor 17 and a large current is supplied to the demagnetization unit 30, and a low-current demagnetization mode in which the power supply 40 is connected to the resistor 17 and a current smaller than the large current mentioned above is supplied to the demagnetization unit 30.

[0044] The demagnetizer 1b (demagnetizing mode switching means 10b) of this embodiment differs from the demagnetizer 1 (demagnetizing mode switching means 10) of the embodiment described above in that it does not have a first resistor 11 connected in series with the demagnetizing unit 30, but instead has a resistor 17 connected in parallel with the demagnetizing unit 30 and having a resistance value (Rsb) smaller than the internal resistance (resistance value: Ri) of the demagnetizing unit 30.

[0045] Furthermore, the resistance value (Rsb) of the resistor 17 is preferably 1 / 3 or less of the resistance value (Ri) of the demagnetizing unit 30 (internal resistance of the demagnetizing unit 30), and more preferably 1 / 10 or less. This makes it possible to sufficiently reduce the influence of power supply-derived noise on the demagnetizing unit 30, as will be described later.

[0046] When using such a demagnetizing device 1b, demagnetization is first performed using a high-current demagnetizing mode that does not conduct to the resistor 17. Specifically, as shown in Figure 8, the switching unit (switch) 18 prevents conduction between the power supply 40 and the resistor 17, and a damped sinusoidal current or damped triangular wave current is supplied from the power supply 40 to the demagnetizing unit 30. In this high-current demagnetizing mode, the demagnetizing operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped.

[0047] Next, the resistor 17 is connected, and demagnetization is performed using a low-current demagnetization mode, which reduces the current in the demagnetization unit 30 to less than that in the high-current demagnetization mode described above. Specifically, as shown in Figure 9, in the switching unit (switch) 18, with the power supply 40 and the resistor 17 connected, a damped sinusoidal current or a damped triangular wave current is supplied from the power supply 40 to the demagnetization unit 30. It is preferable that the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 in the low-current demagnetization mode is the same current (a current with the same magnitude, frequency, damping ratio, etc.) as the high-current demagnetization mode performed prior to the low-current demagnetization mode. In the low-current demagnetization mode as well, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped.

[0048] In the demagnetizer 1b of this embodiment, in the low-current demagnetization mode, the current supplied from the power supply 40 is divided and the current supplied from the power supply 40 is gradually reduced (to a damped sinusoidal current or a damped triangular wave current), thereby reducing the influence of power supply-derived noise, which causes instability of the residual magnetic field, on the demagnetization unit 30.

[0049] Furthermore, even in such a demagnetizer 1b, under the assumptions described above, the magnitude of the effect of reducing the influence of power supply-derived noise on the demagnetizer 30 can be estimated from a theoretical formula. For example, if the magnitude of the noise (superimposed noise current) in the high-current demagnetization mode is "inb", and the resistance values ​​are Ri=1Ω and Rsb=0.1Ω, then the magnitude of the noise (superimposed noise current) in the low-current demagnetization mode is "inb × [Rsb / (Rsb+Ri)]". Therefore, it can be estimated that in the low-current demagnetization mode, the influence of power supply-derived noise on the demagnetizer 30 can be reduced to 1 / 11 compared to the high-current demagnetization mode.

[0050] Next, another embodiment of the demagnetizing device of the present invention will be described using the example shown in the drawings. In the following description, components that are substantially the same as those in the demagnetizing device 1 described above will be given corresponding names and reference numerals, and detailed explanations will be omitted.

[0051] In this embodiment, the power supply 40c connected to the demagnetization unit 30 is a constant voltage power supply capable of supplying a damped sinusoidal current or a damped triangular wave current. As such a power supply, a known product, for example, the bipolar power supply BP4610 manufactured by NF Circuit Design Block Co., Ltd., can be used. Preferably, when the resistance value of the first resistor 19 is 10Ω and the resistance value of the second resistor 20 is 100Ω, the voltage of the power supply 40c can be set in the range of 10V to 100V, and the frequency can be set in the range of 0.1Hz to 10Hz.

[0052] Furthermore, the power supply-derived noise that is the focus of this invention is mainly generated by the amplifier built into the power supply 40c. Therefore, even if the output (in this case, the voltage magnitude) on the power supply 40c side is reduced, the magnitude of the noise does not change significantly. For this reason, the demagnetizer 1c of this embodiment functions effectively.

[0053] As shown in Figures 10 to 12, the demagnetization mode switching means 10c of the demagnetizer 1c of this embodiment includes a first resistor 19 (resistance value: Rlc) that can be connected in series with the demagnetizer 30, a second resistor 20 (resistance value: Rsc) that can be connected in series with the demagnetizer 30 and has a higher resistance value than the first resistor 19, and a switching unit (switch) 21 that switches the connection between the power supply 40c and the first resistor 19 or the second resistor 20. The means 10c is capable of switching between a high-current demagnetization mode when connected to the first resistor 19 and a low-current demagnetization mode when connected to the second resistor 20 (where the current in the demagnetizer 30 is smaller than in the high-current demagnetization mode). In other words, the demagnetizer 1c (demagnetization mode switching means 10c) of this embodiment can switch between a high-current demagnetization mode, in which the power supply 40c is not connected to the second resistor 20 but is connected to the first resistor 19 and a large current is supplied to the demagnetization unit 30, and a low-current demagnetization mode, in which the power supply 40c is not connected to the first resistor 19 but is connected to the second resistor 20 and a current smaller than the high current described above is supplied to the demagnetization unit 30.

[0054] When using such a demagnetizing device 1c, demagnetization is first performed using a high-current demagnetizing mode connected to the first resistor 19. Specifically, as shown in Figure 11, with the power supply 40c and the first resistor 19 connected by the switching unit (switch) 21, a damped sinusoidal current or a damped triangular wave current is supplied from the power supply 40c to the demagnetizing unit 30. In this high-current demagnetizing mode, the demagnetizing operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40c is sufficiently damped.

[0055] Next, the second resistor 20 is connected, and demagnetization is performed using a low-current demagnetization mode, which reduces the current in the demagnetization unit 30 to less than that in the high-current demagnetization mode described above. Specifically, as shown in Figure 12, with the power supply 40c and the second resistor 20 connected in the switching unit (switch) 21, a damped sinusoidal current or a damped triangular wave current is supplied from the power supply 40c to the demagnetization unit 30. It is preferable that the damped sinusoidal current or damped triangular wave current supplied from the power supply 40c in the low-current demagnetization mode is the same current (a current with the same magnitude, frequency, damping ratio, etc.) as the high-current demagnetization mode performed prior to the low-current demagnetization mode. In the low-current demagnetization mode as well, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40c is sufficiently damped.

[0056] In the demagnetizer 1c of this embodiment, in the low-current demagnetization mode, the magnitude of the attenuated sinusoidal current or attenuated triangular wave current flowing through the demagnetization unit 30 is switched (specifically, made smaller than in the high-current demagnetization mode), and the current supplied from the power supply 40c is gradually reduced (to an attenuated sinusoidal current or attenuated triangular wave current), thereby reducing the influence of power supply-derived noise, which causes instability of the residual magnetic field, on the demagnetization unit 30.

[0057] Furthermore, even in such a demagnetizing device 1c, under the assumptions described above, the magnitude of the effect of reducing the influence of power supply-derived noise on the demagnetizing unit 30 can be estimated from the theoretical formula. In other words, if the magnitude of the noise originating from the power supply is "Vn", then in the high-current demagnetization mode, the magnitude of the noise (current noise) flowing through the demagnetization unit 30 via the first resistor 19 is "Vn / R1". In contrast, in the low-current demagnetization mode, the magnitude of the noise (current noise) flowing through the demagnetization unit 30 via the second resistor 20 is "Vn / R2". Therefore, if the resistance values ​​are, for example, R1=10Ω and R2=100Ω, it can be inferred that in the low-current demagnetization mode, the influence of noise originating from the power supply on the demagnetization unit 30 can be reduced to 1 / 10 compared to the high-current demagnetization mode.

[0058] Next, another embodiment of the demagnetizing device of the present invention will be described using the example shown in the drawings. In the following description, components that are substantially the same as those in the demagnetizing device 1 described above will be given corresponding names and reference numerals, and detailed explanations will be omitted.

[0059] As shown in Figures 13 to 15, the demagnetizer 1d of this embodiment includes a first power supply 41 that supplies a damped sinusoidal current or a damped triangular wave current, and a second power supply 42 that supplies a damped sinusoidal current or a damped triangular wave current smaller than that of the first power supply 41. The demagnetization mode switching means 10d can switch between a high-current demagnetization mode using the first power supply 41 and a low-current demagnetization mode using the second power supply 42. In this embodiment, the power-source noise in the second power supply 42 is smaller than the power-source noise in the first power supply 41.

[0060] In this embodiment, the first power supply 41 and the second power supply 42 are constant current power supplies capable of supplying attenuated sinusoidal current or attenuated triangular wave current. The magnitude of the attenuated sinusoidal current or attenuated triangular wave current that the first power supply 41 can supply is preferably 1A to 10A, and the frequency is preferably 0.1Hz to 10Hz. The magnitude of the attenuated sinusoidal current or attenuated triangular wave current that the second power supply 42 can supply is preferably smaller than that of the first power supply 41 and in the range of 0.1A to 1A, and the frequency is preferably 0.1Hz to 1Hz. As the first power supply capable of supplying such attenuated sinusoidal current or attenuated triangular wave current, a known product, such as the bipolar power supply BP4610 manufactured by NF Circuit Design Block Co., Ltd., can be used, and as the second power supply, a known product, such as the intelligent bipolar power supply PBZ20-20 manufactured by Kikusui Electronics Co., Ltd., can be used.

[0061] When using such a demagnetizing device 1d, demagnetization is first performed using a high-current demagnetizing mode with a first power supply 41. Specifically, as shown in Figure 14, with the first power supply 41 connected to the demagnetizing unit 30 by a switching unit (switch) 22, a damped sinusoidal current or a damped triangular wave current is supplied from the first power supply 41 to the demagnetizing unit 30. In this high-current demagnetizing mode, the demagnetizing operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the first power supply 41 is sufficiently damped.

[0062] Next, demagnetization is performed using a low-current demagnetization mode with the second power supply 42. Specifically, as shown in Figure 15, with the second power supply 42 connected to the demagnetization unit 30 by the switching unit (switch) 22, a damped sinusoidal current or a damped triangular wave current is supplied from the second power supply 42 to the demagnetization unit 30. It is preferable that the damped sinusoidal current or damped triangular wave current supplied from the power supply 42 in the low-current demagnetization mode has the same frequency and damping ratio as the high-current demagnetization mode performed prior to the low-current demagnetization mode. In the low-current demagnetization mode as well, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the second power supply 42 is sufficiently damped.

[0063] In the demagnetizer 1d of this embodiment, in the low-current demagnetization mode, the magnitude of the attenuated sinusoidal current or attenuated triangular wave current flowing through the demagnetization unit 30 is switched (specifically, made smaller than in the high-current demagnetization mode), and the current supplied from the power supplies 41 and 42 is gradually reduced (to an attenuated sinusoidal current or attenuated triangular wave current), thereby reducing the influence of power supply-derived noise, which causes instability of the residual magnetic field, on the demagnetization unit 30.

[0064] Next, an embodiment of the demagnetization mode switching device of the present invention will be described using the example shown in the drawings. In the following description, components that are substantially the same as those of the demagnetization device 1 described above will be given corresponding names and reference numerals, and detailed explanations will be omitted.

[0065] As shown in Figures 16 and 17, the demagnetization mode switching device 100 of the present invention is a demagnetization mode switching device 100 for a demagnetization device that includes a power supply 40 that supplies a damped sinusoidal current or a damped triangular wave current to reduce the residual magnetic field of a magnetic shielding device 5 equipped with magnetic shielding members 51 and 52 that shield from external magnetic fields, and a demagnetization unit 30 connected to the power supply 40 and disposed relative to the magnetic shielding members. The demagnetization mode switching device 100 includes a demagnetization mode switching means 10e that switches the magnitude of the attenuated sinusoidal current or attenuated triangular wave current (including noise current) flowing through the demagnetization unit 30. The demagnetization mode switching means 10e includes a first resistor 23 (resistance value: Rle) connected in series with the demagnetization unit 30, a second resistor 24 (resistance value: Rse) connected in parallel with the demagnetization unit 30 and the first resistor 23, and a switching unit (switch) 25 that switches whether or not there is continuity between the power supply 40 and the second resistor 24. The device can switch between a high-current demagnetization mode in which there is no continuity through the second resistor 24 and a low-current demagnetization mode in which there is continuity through the second resistor 24. In the low-current demagnetization mode, the magnitude (maximum value) of the current flowing through the demagnetization unit 30 is smaller than the magnitude (maximum value) of the current flowing through the demagnetization unit 30 in the high-current demagnetization mode. In other words, the demagnetization mode switching device 100 (demagnetization mode switching means 10e) of this embodiment can switch between a high-current demagnetization mode in which the second resistor 24 is not connected to the power supply 40 and the first resistor 23 is connected to the power supply 40, thereby supplying a large current to the demagnetization unit 30, and a low-current demagnetization mode in which the second resistor 24 is connected to the power supply 40, thereby supplying a current smaller than the high current described above to the demagnetization unit 30 and the first resistor 23.

[0066] In other words, the demagnetization mode switching device 100 is the demagnetization device 1 described above, with the demagnetization unit 30 (and power supply 40) removed. That is, in the embodiment shown in Figures 16 and 17, the demagnetization unit 30 is a demagnetization unit 30 that has been pre-installed on the magnetic shielding device 5, and reference numeral 26 in Figures 16 and 17 indicates the connection between the demagnetization mode switching device 100 and the demagnetization unit 30.

[0067] It is preferable that the second resistor 24 has a resistance value (Rse) smaller than the sum of the resistance value (Rle) of the first resistor 23 and the resistance value (Ri) of the demagnetizing unit 30 (internal resistance of the demagnetizing unit 30). Furthermore, it is preferable that the resistance value (Rse) of the second resistor 24 be 1 / 3 or less, and more preferably 1 / 10 or less, of the sum of the resistance value (Rle) of the first resistor 23 and the resistance value (Ri) of the demagnetizing unit 30 (internal resistance of the demagnetizing unit 30).

[0068] The operation for demagnetizing the magnetic shielding device 5 using the demagnetization mode switching device 100 of this embodiment will be described below. Prior to performing the demagnetization operation, the demagnetization mode switching device 100 is connected to the prepared power supply 40 and the demagnetization unit 30 installed in the magnetic shielding device 5, as shown in Figure 16. In Figure 16, reference numeral 14e indicates the connection between the demagnetization mode switching device 100 and the power supply 40, and reference numeral 26 indicates the connection between the demagnetization mode switching device 100 and the demagnetization unit 30, as described above.

[0069] Using the demagnetization mode switching device 100, demagnetization is first performed using a high-current demagnetization mode in which the second resistor 24 is not connected. Specifically, as shown in Figure 16, the switching unit (switch) 25 disconnects the power supply 40 from the second resistor 24, and supplies a damped sinusoidal current or a damped triangular wave current from the power supply 40 to the demagnetization unit 30. In this high-current demagnetization mode, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped.

[0070] Next, the second resistor 24 is connected, and demagnetization is performed using a low-current demagnetization mode, which reduces the current in the demagnetization unit 30 to less than that in the high-current demagnetization mode described above. Specifically, as shown in Figure 17, in the switching unit (switch) 25, with the power supply 40 and the second resistor 24 connected, a damped sinusoidal current or damped triangular wave current is supplied from the power supply 40 to the demagnetization unit 30. It is preferable that the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 in the low-current demagnetization mode is the same current (a current with the same magnitude, frequency, damping ratio, etc.) as the high-current demagnetization mode performed prior to the low-current demagnetization mode. In the low-current demagnetization mode as well, the demagnetization operation is continued until the damped sinusoidal current or damped triangular wave current supplied from the power supply 40 is sufficiently damped.

[0071] The demagnetization mode switching device 100 of this embodiment divides the demagnetization operation into at least two stages: demagnetization with a large current (large current demagnetization mode) and demagnetization with a small current (small current demagnetization mode). In the first stage (large current demagnetization mode), the power supply 40 is directly connected to the demagnetization unit 30. In the second stage (small current demagnetization mode), the second resistor 24 is connected in parallel with the demagnetization unit 30 via the switching unit (switch) 25, thereby dividing the current supplied from the power supply 40 and enabling demagnetization with low noise in the demagnetization unit 30.

[0072] In other words, in the second stage (low-current demagnetization mode), by dividing the current supplied from the power supply 40 and gradually reducing the current supplied from the power supply 40 (to a damped sinusoidal current or a damped triangular wave current), it is possible to reduce the influence of power supply-derived noise, which causes instability of the residual magnetic field, on the demagnetization unit 30. Furthermore, in such a demagnetization mode switching device 100, noise superimposed on the demagnetization current can be reduced in a practical (relatively small and inexpensive) manner using existing resistors and switches, without the need for a large transformer.

[0073] Furthermore, the power supply-derived noise that is the focus of this invention is mainly generated by the amplifier built into the power supply 40. Therefore, even if the output (in this case, the magnitude of the current) on the power supply 40 side is reduced, the magnitude of the noise does not change significantly. For this reason, the demagnetization mode switching device 100 of this embodiment functions effectively.

[0074] Furthermore, the magnitude of the above effect (the effect of reducing the influence of power supply-derived noise on the demagnetizing unit 30) can also be estimated from the theoretical formula. The influence of noise (superimposed noise current) in the attenuated sinusoidal current or attenuated triangular current supplied by power supply 40 depends on the nature and time (time from the start of current supply) of the current. However, in the following comparison, we assume that the comparison is under the same nature and time, and we will estimate by ignoring (canceling out) the influence of those parameters. Under the above assumptions, let "ine" be the magnitude of the noise (superimposed noise current) in the high-current demagnetization mode. In contrast, the magnitude of the noise (superimposed noise current) in the low-current demagnetization mode is "ine × [Rse / (Rse + Rle + Ri)]". Therefore, if we set the resistance values ​​to, for example, Ri = 1Ω, Rse = 1Ω, and Rle = 10Ω, it can be inferred that in the low-current demagnetization mode, the influence of power supply-derived noise on the demagnetization unit 30 can be reduced to 1 / 12 compared to the high-current demagnetization mode. [Explanation of Symbols]

[0075] 1,1a,1b,1c,1d Degaussing device 10, 10a, 10b, 10c, 10d, 10e Demagnetization mode switching means 100 Demagnetization mode switching device 11, 12,15,17,19,20,23,24 resistor 13, 16, 18, 21, 22, 25 Switching section 30 Demagnetizing section 40 Power supply 5. Magnetic shielding device 50 Main body of the device 51, 52 Magnetic shielding member

Claims

1. A demagnetizing device for reducing the residual magnetic field of a magnetic shielding device equipped with a magnetic shielding member that shields against external magnetic fields, A demagnetizing unit is connected to a power supply that provides a damped sinusoidal current or a damped triangular wave current, and is disposed relative to the magnetic shielding member, A demagnetization mode switching means for switching the magnitude of the attenuated sinusoidal current or attenuated triangular wave current flowing through the demagnetization section, A demagnetizing device characterized by being equipped with the following features.

2. A demagnetizing device for reducing the residual magnetic field of a magnetic shielding device equipped with a magnetic shielding member that shields against external magnetic fields, A power supply that provides a damped sinusoidal current or a damped triangular wave current, A demagnetizing unit connected to the power supply and disposed relative to the magnetic shielding member, A demagnetization mode switching means, located outside the power supply, which switches the magnitude of the attenuated sinusoidal current or attenuated triangular wave current flowing through the demagnetization section, A demagnetizing device characterized by being equipped with the following features.

3. The demagnetization mode switching means comprises a resistor connected in parallel with the demagnetization unit, and a switching unit that switches between the presence or absence of conductivity between the power supply and the resistor. The resistor has a resistance value smaller than that of the demagnetizing section. The demagnetizing device according to claim 1 or 2, which is capable of switching between a high-current demagnetizing mode in which the resistor is not conductive and a low-current demagnetizing mode in which the resistor is conductive.

4. The demagnetizing device according to claim 3, wherein the resistance value of the resistor is 1 / 3 or less of the resistance value of the demagnetizing unit.

5. The demagnetization mode switching means comprises a first resistor connected in series with the demagnetization unit, a second resistor connected in parallel with the demagnetization unit and the first resistor, and a switching unit that switches between continuity between the power supply and the second resistor. The second resistor has a resistance value smaller than the sum of the resistance value of the first resistor and the resistance value of the demagnetizing section. The demagnetizing device according to claim 1 or 2, which is capable of switching between a high-current demagnetizing mode in which the second resistor is not connected and a low-current demagnetizing mode in which the second resistor is connected.

6. The demagnetizing device according to claim 5, wherein the resistance value of the second resistor is 1 / 3 or less of the sum of the resistance value of the first resistor and the resistance value of the demagnetizing unit.

7. The demagnetization mode switching means comprises a first resistor that can be connected in series with the demagnetization unit, a second resistor that can be connected in series with the demagnetization unit and has a greater resistance value than the first resistor, and a switching unit that switches the connection between the power supply and the first resistor or the second resistor. The demagnetizing device according to claim 1 or 2, which is capable of switching between a high-current demagnetizing mode when connected to the first resistor and a low-current demagnetizing mode when connected to the second resistor.

8. The demagnetizing device comprises a first power supply that supplies a damped sinusoidal current or a damped triangular wave current, and a second power supply that supplies a damped sinusoidal current or a damped triangular wave current smaller than that of the first power supply. The demagnetizing device according to claim 1 or 2, wherein the demagnetizing mode switching means is capable of switching between a high-current demagnetizing mode using the first power supply and a low-current demagnetizing mode using the second power supply.

9. The demagnetizing device according to claim 1 or 2, wherein the magnetic shielding device comprises two or more layers of magnetic shielding members, and the demagnetizing unit is disposed relative to the innermost layer of the magnetic shielding member.

10. A demagnetization mode switching device for a demagnetization device comprising: a power supply that supplies a damped sinusoidal current or a damped triangular wave current to reduce the residual magnetic field of a magnetic shielding device equipped with a magnetic shielding member that shields from external magnetic fields; and a demagnetization unit connected to the power supply and disposed relative to the magnetic shielding member, The demagnetization mode switching device includes a demagnetization mode switching means for switching the magnitude of the attenuated sinusoidal current or attenuated triangular wave current flowing through the demagnetization section. The demagnetization mode switching means comprises a first resistor connected in series with the demagnetization unit, a second resistor connected in parallel with the demagnetization unit and the first resistor, and a switching unit that switches between continuity between the power supply and the second resistor. A demagnetization mode switching device characterized by being able to switch between a high-current demagnetization mode in which the second resistor is not conductive and a low-current demagnetization mode in which the second resistor is conductive.

11. The demagnetization mode switching device according to claim 10, wherein the second resistor has a resistance value smaller than the sum of the resistance value of the first resistor and the resistance value of the demagnetization unit.

12. The demagnetization mode switching device according to claim 10, wherein the resistance value of the second resistor is 1 / 3 or less of the sum of the resistance value of the first resistor and the resistance value of the demagnetization unit.

Images