AU2011344940A1

AU2011344940A1 - Device and method for measuring magnetic induction intensity based on colossal magnetoresistive effect

Info

Publication number: AU2011344940A1
Application number: AU2011344940A
Authority: AU
Inventors: Yusheng Li; Jiangyi Wang; Xin Wang; Jie Zheng; Ming ZHUANG; Ciyuan Zhuo
Original assignee: State Grid Corp of China SGCC; State Grid Fujian Electric Power Co Ltd; Fujian Shuikou Power Generation Group Co Ltd
Current assignee: State Grid Corp of China SGCC; State Grid Fujian Electric Power Co Ltd; Fujian Shuikou Power Generation Group Co Ltd
Priority date: 2010-12-16
Filing date: 2011-12-14
Publication date: 2013-07-04
Anticipated expiration: 2031-12-14
Also published as: CN102103193A; AU2011344940B2; CN102103193B; WO2012079507A1

Abstract

The invention refers to a device and method for measuring magnetic induction intensity, especially to a device and method for measuring magnetic induction intensity based on the colossal magnetoresistive effect. The device includes an electromagnetic shielding device, a first loop and a second loop; the first loop includes a colossal magnetoresistive element, a Helmholtz coil and a first power supply device; the second loop includes a Huygens bridge and a second power supply device. The Helmholtz coil is utilized to supply a counter magnetic field by the use of significant action of the colossal magnetoresistive effect, so as to balance a magnetic field to be measured. When the Huygens bridge is balanced, the magnetic field to be measured is numerically equal to the magnetic field of the Helmholtz coil, but their directions are opposite, therefore, the device is not required to calculate the resistance of the colossal magnetoresistive element, thereby improving calculation accuracy and precision. The electromagnetic shielding device is utilized to effectively shield the environmental magnetic field, provide a measuring environment with zero magnetic field intensity, provide basic parameters without interference for the subsequent measuring, and improve the measuring accuracy.

Description

DEVICE AND METHOD FOR MEASUREING MAGNETIC INDUCTION INTENSITY BASED ON COLOSSAL MAGNETORESISTIVE EFFECT FIELD OF THE INVENTION The invention relates to a device and method for measuring magnetic induction intensity, especially a device and method for measuring magnetic induction intensity based on the colossal magnetoresistive effect. BACKGROUND OF THE INVENTION Magnetic induction intensity scale is broadly used. The present art to measure the magnetic induction intensity is mainly using the Helmholtz sensor or the magnetic induction coil. Particularly, the Helmholtz sensor mentioned herewith is widely applied for its simple structure and small-scale. However, in practical use, the level of noise and static offset of Helmholtz sensor is relatively high, so that the measurement of weak magnetic field is unable to provide desired sensitivity and precision; while the magnetic induction coil, which is operated by Faraday's Law, can not be utilized in measuring the intensity of static magnetic field, and is mainly applied in close-distance detection, The measuring of magnetic induction intensity can also be accomplished by taking advantage of magnetoresistive effect of specific material. Said magnetoresistive effect (MR), refers to the phenomenon of resistance variation of material under the effect of magnetic field. The MR value of magnetic metal and alloy are normally below 8% under general room temperature. Yet the MR value of magnetic/nonmagnetic metallic multilayer films is usually 10 or so, which is so-called giant magnetoresistive effect (GMR). In recent years, said GMR material is broadly applied in the hard drives of computers and numerical control machines. While the MR value of conventional GMR material is still not high enough. SUMMARY OF THE INVENTION To overcome aforementioned disadvantages, present invention provides an accurate and dependable device and method for measuring magnetic induction intensity based on the colossal magnetoresistive effect, said device comprises: An electro-magnetic shielding device; A first loop includes a colossal magnetoresistive element, a Helmholtz coil and a first power supply device, and Said colossal magnetoresistive element is placed at the central point of said Helmholtz coil's axis; Said Helmholtz coil which contains colossal magnetoresistive element is connected with said first power supply device to form said first loop; A second loop includes a Wheatstone bridge and a second power supply device; Said Wheatstone bridge is connected to said second power supply device to form said second loop; Meanwhile, said colossal magnetoresistive element is connected to the position of the measuring resistance of said Wheatstone bridge. Said device for measuring magnetic induction intensity based on the colossal magnetoresistive effect, is operated by following steps: 1. Open said first loop and close said second loop, then place the whole device into said electro-magnetic shielding device, meanwhile, said colossal magnetoresistive element is inside a measuring environment with zero magnetic field intensity; 2. Adjust the resistance box of said Wheatstone bridge until the Wheatstone bridge is balanced. 3. Keep the resistance value of said Wheatstone bridge unchanged, and remove said electro-magnetic shielding device to expose the device to the magnetic field to be measured. 4. Due to the colossal magnetoresistive effect, the resistance of said colossal magnetoresistive element decreases dramatically, so the balance of said Wheatstone bridge is broken. 5. Close said first loop and make a magnetic field occur in said Helmholtz coil, meanwhile, said colossal magnetoresistive element is affected by both the magnetic field in said Helmholtz coil and the magnetic field to be measured, and the total environment magnetic field is composed of above-mentioned two magnetic fields. 6. Adjust said first power supply device to change the direction and strength of the current through said Helmholtz coil, until the Wheatstone bridge is once again balanced. 7. At this time, the resistance value of said colossal magnetoresistive element is equal to the resistance value in the environment with zero-intensity magnetic field. This indicates the total intensity of environmental magnetic field where said colossal magnetoresistive element lies is zero. Thus the magnetic field to be measured and the magnetic field in said Helmholtz coil are balanced. The two magnetic fields have same intensity but opposite direction. 8. The value of present magnetic induction intensity can be calculated according to the coil numbers, current intensity and the radius of said Helmholtz coil. Said colossal magnetoresistive element is composed of colossal magnetoresistive material which can produce colossal magnetoresistive effect. Under certain temperature and magnetic field, said colossal magnetoresistive material transfers from paramagnetic or antiferromagnetic to ferromagnetic, and its resistivity decreases by orders of magnitude. This effect could reach up to 106 and is so called colossal magnetoresistive effect (CMR) which is 105 times of GMR. Therefore, it can be used for precise measuring of magnetic field, particularly for that of weak magnetic field. Besides, present invention uses said Helmholtz coil to provide reverse magnetic field which balances the magnetic field to be measured; and uses said Wheatstone bridge to indicate whether the total environmental magnetic field intensity is zero. When the intensity of total environmental magnetic field is zero, the magnetic field to be measured is balanced with the magnetic field of said Helmholtz coil by the same intensity and opposite direction. Thus, it does not need to calculate the resistivity of colossal magnetoresistive element, thereby simplifying the calculation. Furthermore, due to high sensitivity of said Wheatstone bridge, and the application of electro-magnetic shielding device to provide environment with zero magnetic intensity, the accuracy and precision of the measurement is guaranteed. The further detailed description of present invention could be specific to that: Said colossal magnetoresistive element comprises a thin film of Rare Earth Manganese oxide with an ABO3 Perovskite structure, and said film is deposited on the Al20 3 substrate by the method of pulsed laser deposition. The film can produce colossal magnetoresistive effect, and therefore be applied in producing colossal magnetoresistive elements. Said Rare Earth Manganese oxide thin film, which is used in colossal magnetoresistive element, is a doped Rare Earth Manganese oxide with formula of LaxR-xMnO 3 , where R ion is a bivalent metal element such as calcium. The Application of said Rare Earth Manganese oxide promotes the CMR occurring temperature range to the common room temperature, thereby making adapted environment much broader and the manufacture of device of measuring weak magnetic field more convenient. Said Helmholtz coil is assembled by a pair of round coils, which are exactly same and be disposed in parallel and coaxial. The distance between said coils is numerically equal to their radius. Thus, when these 2 coils conduct current in same direction, the whole magnetic field intensity of said coils are evenly spread around the central point of axis and balanced with the measuring magnetic field intensity. Said first and second power supply devices are stable voltage direct-current power sources, of which the adaptive voltage is within the range of 10 - 200 V. The adjustment range of the output voltage of said power supply device shall correspond to the parameters of said Helmholtz coil, so as to adjust the current strength in said Helmholtz coil, and the direction of current is controlled by polarity.

Said electro-magnetic shielding device is a shield made of wire nets. It is mainly used for shielding environmental electromagnetic field and providing the measuring environment with zero magnetic field intensity. Conclude by aforementioned, present invention provides an accurate and dependable device and method for measuring magnetic induction intensity based on the colossal magnetoresistive effect, applies Helmholtz coil to provide reversal magnetic field to balance the measuring magnetic field; applies Wheatstone bridge to indicate whether the intensity of total environmental magnetic field is zero. When the intensity of total environmental magnetic field is zero, the magnetic field to be measured is balanced with the magnetic field of said Helmholtz coil. The two magnetic fields have same intensity but opposite direction. Due to the high sensitivity of Wheatstone bridge, the accuracy and precision of the measurement are upgraded. Electro-magnetic shielding device is utilized to block environmental magnetic field effectively, thus provides a measure environment with zero magnetic field intensity, and the accuracy of continuing measurement is ensured. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is the scheme of the operating principle of the first loop in present invention. Fig. 2 is the scheme of the operating principle of the second loop in present invention. Fig. 3 is the scheme of working principle of the execution of measuring when environmental magnetic field is blocked by electro-magnetic shielding device. Fig. 4 is the scheme of working principle of the execution of measuring when the electro-magnetic shielding device is removed. DETAILED DESCRIPTION OF REFFERED EMBODIMENT Present invention is further described with an embodiment as following: A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect comprises an electro-magnetic shielding device, a first loop and a second loop U1. Refer Fig. 1, said first loop includes a colossal magnetoresistive element which is LaCaMnO, a Helmholtz coil and a first power supply device U1, said colossal magnetoresistive element LaCaMnO is placed at the central point of said Helmholtz coil's axis; the Helmholtz coil, in which the colossal magnetoresistive element is installed, is connected to U1 through KI to form the first loop. Wherein said colossal magnetoresistive element comprises a film of La 0

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7

R

0

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3 MnO 3 which is a kind of doped Rare Earth Manganese oxide and said film is deposited on the Al2O 3 substrate by the method of pulsed laser deposition. And said Helmholtz coil is assembled by a pair of round coils, which are exactly same and be disposed in parallel and coaxial, the distance between said coils is numerically equal to the radius of said coil. Refer Fig. 2, the second loop includes a Wheatstone bridge and a second power supply device U2, said Wheatstone bridge is connected to U2 through K2 to form the second loop. Said first power supply device U1 and second power supply device U2 are stable voltage direct-current power sources, and the adaptive voltage is within the range of 10 - 200 V. The electro-magnetic shielding device is a shield which is made of wire nets and mainly used for blocking environmental electromagnetic field to provide a measure environment with zero magnetic field intensity. Refer Figs. 3 and 4, said device for measuring magnetic induction intensity based on the colossal magnetoresistive effect is operated by following steps: 1. Refer Fig. 3, open KI to open the first loop, while close K2 to close the second loop, then place the whole measuring device into said electro-magnetic shielding device. Because there is no current in said first loop, the magnetic field does not occur in the Helmholtz coil. Also the environmental magnetic field is blocked by said electro-magnetic shielding device, Thus, said colossal magnetoresistive element LaCaMnO is inside a measuring environment with zero magnetic field intensity; 2. Adjust the resistance value Rt of the resistance box of said Wheatstone bridge until the scale reading of the current meter G reaches zero. At this time, the Wheatstone bridge is balanced. 3. Refer Fig. 4, keep the resistance value Rt of said Wheatstone bridge unchanged, and remove said electro-magnetic shielding device to expose the measuring device into the magnetic field to be measured. 4. Under the effect of the magnetic field to be measured, the resistance of said colossal magnetoresistive element LaCaMnO decreases dramatically due to the colossal magnetoresistive effect, the balance of said Wheatstone bridge is broken, and the scale reading of the current meter G is not yet zero. 5. Close KI to close said first loop and make magnetic field occur in said Helmholtz coil, at this time, said colossal magnetoresistive element LaCaMnO is affected by both the magnetic field in said Helmholtz coil and the magnetic field to be measured, the sum of the intensity value of the magnetic field in said Helmholtz coil and the magnetic field to be measured is the total intensity value of environmental magnetic field. 6. Adjust said first power supply device U1 to change the direction and strength of the current through said Helmholtz coil, until the scale reading of the current meter G becomes zero, which suggests that the Wheatstone bridge is once again balanced. 7. At this time, the resistance value of said colossal magnetoresistive element is equal to the resistance value in the environment with zero-intensity magnetic field, which indicates the total intensity of environmental magnetic field is zero. Thus the magnetic field B 1 to be measured and the magnetic field B2 in said Helmholtz coil are balanced. The two magnetic fields have same intensity but opposite direction, which can be described as B1=-B2. 8. The value of present magnetic induction intensity can be calculated according to the coil numbers, current intensity and the radius of said Helmholtz coil. Aforementioned device and method can be adapted with varies types of electrical facilities. Aforementioned device and method is capable of measuring not only the intensity of magnetic field, but also the strength of electric field when innovated properly. Else details of present invention which are not described herewith are the same with the prior art.

Claims

1. A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect, comprises: An electro-magnetic shielding device; A first loop includes a colossal magnetoresistive element, a Helmholtz coil and a first power supply device, and Said colossal magnetoresistive element is placed at the central point of said Helmholtz coil's axis; Said Helmholtz coil which contains colossal magnetoresistive element is connected with said first power supply device to form said first loop; A second loop includes a Wheatstone bridge and a second power supply device; Said Wheatstone bridge is connected to said second power supply device to form said second loop; Meanwhile, said colossal magnetoresistive element is connected to the position of the measuring resistance of said Wheatstone bridge.

2. A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect according to claims, is operated by following steps: (1) Open said first loop and close said second loop, then place the whole device into said electro-magnetic shielding device, meanwhile, said colossal magnetoresistive element is inside a measuring environment with zero magnetic field intensity; (2) Adjust the resistance box of said Wheatstone bridge until the Wheatstone bridge is balanced. (3) Keep the resistance value of said Wheatstone bridge unchanged, and remove said electro-magnetic shielding device to expose the device to the magnetic field to be measured. (4) Due to the colossal magnetoresistive effect, the resistance of said colossal magnetoresistive element decreases dramatically, so the balance of said Wheatstone bridge is broken. (5) Close said first loop and make a magnetic field occur in said Helmholtz coil, meanwhile, said colossal magnetoresistive element is affected by both the magnetic field in said Helmholtz coil and the magnetic field to be measured, and the total environment magnetic field is composed of above-mentioned two magnetic fields. (6) Adjust said first power supply device to change the direction and strength of the current through said Helmholtz coil, until the Wheatstone bridge is once again balanced. (7) At this time, the resistance value of said colossal magnetoresistive element is equal to the resistance value in the environment with zero-intensity magnetic field, which indicates the total intensity of environmental magnetic field is zero. Thus the magnetic field to be measured and the magnetic field in said Helmholtz coil are balanced. The two magnetic fields have same intensity but opposite direction. (8) The value of present magnetic induction intensity can be calculated according to the coil numbers, current intensity and the radius of said Helmholtz coil.

3. A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect according to claims and claim2, wherein said colossal magnetoresistive element comprises a thin film of Rare Earth Manganese oxide with an ABO3 Perovskite structure, and said film is deposited on the Al20 3 substrate by the method of pulsed laser deposition.

4. A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect according to claim3, wherein said Rare Earth Manganese oxide with an ABO3 Perovskite structure, which is used in colossal magnetoresistive element, is a doped Rare Earth Manganese oxide where A ion is replaced by calcium. So it is a doped Rare Earth Manganese oxide with formula of LaxR-xMnO 3 .

5. A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect according to claims and claim2, wherein said Helmholtz coil is assembled by a pair of round coils, which are exactly same and be disposed in parallel and coaxial, the distance between said coils is numerically equal to the radius of said coil.

6. A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect according to claims and claim2, wherein said first and second power supply devices are stable voltage direct-current power sources, of which the adaptive voltage is within the range of 10-200V.

7. A device for measuring magnetic induction intensity based on the colossal magnetoresistive effect according to claims and claim2, wherein said electro-magnetic shielding device is a shield made of wire nets.