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Development history of magnetic declination measurement equipment for rare earth permanent magnet materials
Release time:
2019-12-21
Source:
Www.fe2100.com
Hunan Yongyi Technology Co., Ltd. began to research and develop magnetic moment and magnetic declination testing equipment in 2010. In 2011, it cooperated with German matesyGmbH Company to introduce "M-axisStandard magnetic declination measuring equipment" into China. M-axisStandard magnetic declination measuring equipment is an innovative magnetic declination measuring equipment. Its principle is to use magnetoresistive matrix to test the spatial magnetic field distribution of permanent magnets, and to obtain the magnetic moment and magnetic declination of magnets by mathematical calculation, which is different from the traditional coil method.
With the development of permanent magnet sensors and high-end magnetic field design, it is necessary to accurately measure and evaluate the magnetic moment and magnetic declination angle of the permanent magnet material devices used. This year, the state and enterprises have jointly carried out: the national standard TC68 of permanent magnet ferrite includes a series of new standard proposals (new test methods for magnetic flux and magnetic moment of permanent magnet ferrite), preparation of standard samples of permanent magnet magnetic moment, calibration specification of magnetic field coil, test standard for magnetic declination angle of magnetic field (group standard), test standard for magnetic moment (proposed group standard) and other work discussions related to magnetic moment and magnetic declination angle of permanent magnet devices.
The measurement of magnetic moment and magnetic declination of permanent magnet materials has become a large-scale test equipment on the market, and has begun to attract the attention of the industry.
The earliest product of magnetic declination measurement of rare earth permanent magnet devices can be traced back to the manufacture of three-dimensional Helmholtz coil method equipment produced by LDJ in the United States in the 1980 s, which may have limited the development of this product due to the lack of demand at that time.
Hunan Yongyi Technology Co., Ltd.
The research and development of magnetic moment and magnetic declination testing equipment began in 2010. In 2011, it cooperated with matesy GmbH Company of Germany to introduce "M-axis Standard magnetic declination measuring equipment" into China. M-axis Standard magnetic declination measuring equipment is an innovative magnetic declination measuring equipment. Its principle is to use magnetoresistive matrix to test the spatial magnetic field distribution of permanent magnets, and to obtain the magnetic moment and magnetic declination of magnets by mathematical calculation, which is different from the traditional coil method. The following two test methods are introduced:
The principle difference between the 1. coil method magnetic declination equipment and the new M-axis test equipment:
1、
Helmholtz coilMethod measurement: uniaxial or triaxial
Helmholtz coilThe three magnetic moment components Mx, My and Mz are tested respectively, and the total magnetic moment M and magnetic declination θz can be obtained by simple mathematical calculation.
2. M-axis magnetic moment scalar method: a matrix distributed magnetic field sensor is used to test the spatial magnetic field distribution B1, B2..., Bn of the permanent magnet device, and the total magnetic moment M and magnetic declination angle θz are obtained through more complex mathematical calculations.
2. parameters that can be derived:
Both methods are indirect calculations of the remanence Br, because they can be calculated by the magnetic moment. Specifically: Bdi = m/(v× 108)(Gs),Br = Bdi×(urec + PC)/(PC +1). The recovery permeability μrec of sintered NdFeB material is approximately equivalent to 1.05, and the permeability coefficient PC value is only considered to be related to the geometric aspect ratio of the magnet, which can be calculated by the shape of the magnet. At present, it is better to calculate the cylinder, ring and square, with an accuracy of about 2%.
3. test accuracy:
A measurement system should not only measure the value, but also ensure its accuracy. Even though any measurement system is not immune to errors, there are ways to reduce its range. In general, there are two main types of errors to consider, namely mean deviation and uncertainty. The following will compare two different measurement methods from these two aspects.
1、
Helmholtz coilThe main sources of deviation are the accuracy of the Helmholtz constant calibration and the accuracy of the fluxmeter. Matters needing attention are:
1-1. Design of coil structure: If the magnetic moment signal in the direction of the main axis of the test sample is strong, it can be used as the outermost coil of the three axes to reduce the difficulty of processing, the induction in the direction of the non-main axis is weak, and the number of turns of the coil is increased as much as possible to improve the resolution. The structure has been imitated by other enterprises after we use.
1-2. Accurate calibration of coil constant: high-precision constant current power supply and
GaussiometerCalibrate.
1-3. Inspection of uniform area of coil: multi-point inspection can be carried out by gaussmeter.
1-4, coil orthogonality test: the use of three-dimensional gauss meter for inspection, the use of square magnetic steel rotation measurement for fine-tuning of the platform surface.
1-5、
magnetic flux meterCalibration can be done with a volt-second generator or a high-grade flux meter.
2. The main deviation sources of the M-axis magnetic moment scalar method are the linearity and installation positioning accuracy of the sensor. The linearity can be calibrated in a standard magnetic field, and the positioning accuracy can be corrected by a standard sample. Matesy GmbH keeps the standard sample transferred by German PTB.
4. uncertainty
Helmholtz coilmethod and M-axis magnetic moment scalar method corresponding to the signal to noise reduction method is not quite the same. Although the sources of deviation are derived from ambient magnetic signal and electrical signal noise, as well as unforeseen operating errors caused by the operator. However, Helmholtz coil method mainly comes from drift and external magnetic field fluctuation, so it needs to be used in areas with relatively clean environmental magnetic field. Generally, the magnetic field fluctuation is required to be less than 10n to 100nT, which can be determined according to the expansion area of the test coil. M-axis magnetic moment scalar method is only related to random distribution results, it can also eliminate drift in irrelevant frequency domain through filters, but the use environment requires no influence of permanent magnetic field, matesy GmbH has done a good job in this area.
Hunan Yongyi Technology Co., Ltd.In November 2019, the magnetic declination test equipment for eliminating field interference magnetic moments was completed, which will be used in the workshop environment and lay the foundation for automated measurement.
Inspection of 5. magnetic declination test equipment
At present, there is no inspection standard related to magnetic moment and magnetic declination. According to our experience in production equipment in the past 10 years, the following methods can be used to evaluate the overall magnetic declination test equipment:
1. Put the magnetic steel into the test coil at any attitude to check the consistency of the total magnetic moment M;
2. Use a wedge block with a fixed angle added to the magnetic steel to check the accuracy of the magnetic declination.
Hunan Yongyi Technology Co., Ltd.At present, it is one of the major suppliers of magnetic declination testing equipment in China (10 years after my QQ log began with "Design of Automatic Magnetic declination Measuring Device"). It has introduced several M-axis magnetic moment magnetic declination testing equipment produced by Matesy GmbH in Germany into Chinese enterprises, but M-axis it has become an obstacle to everyone's recognition because it is different from the traditional innovative testing methods. This is a pity! The company stopped acting as a M-axis in 2013, and in the same year Matesy GmbHz General Manager Hendryk Richert visited Eternal Technology and praised it.
FE-2100AM magnetic moment magnetic declination measuring equipmentIt is the best equipment for testing magnetic declination by coil method he has investigated! Since 2013, Hunan Yongyi Technology Co., Ltd. has provided domestic and foreign users
FE-2100AM declination test equipment45 sets.
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