Decree No. 72 / 2004 Coll.
Order setting out the requirements for measurement assemblies for the measurement of magnetic characteristics of magnets
Valid
Effective from 01.03.2004
72
DECLARATION
of 3 February 2004
laying down requirements for measurement assemblies for the measurement of magnetic characteristics
The Ministry of Industry and Trade provides pursuant to Section 27 of Act No. 505 / 1990 Coll., on Metrology, as amended by Act No. 119 / 2000 Coll. and Act No. 137 / 2002 Coll., ("the Act") for the implementation of Sections 6 (2) and 9 (1) of the Act:
This Decree sets out the requirements for measurement assemblies for the measurement of magnetic characteristics of magnets (hereinafter referred to as the "measurement assembly '), the procedure for type approval and the procedure for verification.
The terminology, the requirements for metering assemblies as well as the procedure for type-approval of metering assemblies and their verification procedure are set out in the Annex.
This Decree shall take effect on 1 March 2004.
Minister:
Ing. Urban v. r.
Annex to Decree No 72 / 2004 Coll.
1 TERMINOLOGY
1.1 The measurement assembly is used to measure magnetic characteristics of magnets in a closed magnetic circuit, i.e. static boundary hysteresis loops (whole or part of the 2nd quadrant called the demagulation curve) and its significant points. It shall consist of the instruments and equipment specified in paragraphs 2.1 and 2.2.
1.2 An etalon sample of magnetic characteristics (hereinafter referred to as the "etalon sample") belonging to the measurement assembly is a sample meeting the requirements of this decree and used exclusively for metrological continuity of the measurement assembly.
1.3 The etalon measurement set-up is the measurement set-up referred to in point 1.1, which is held by the metrology institution, is monitored over a long period of time and is internationally compared through ethalon samples.
1.4 Measurement of the magnet characteristics according to this standard concerns the measurement of both magnetic induction B and magnetic polarisation J of the magnetic field H. These variables are related according to the equation:
B = μ0H + J, (1)
where
B is the magnetic induction in T,
μ0 is the magnetic constant 4pi. 10-7 in H / m,
H is the magnetic field intensity in A / m,
J is a magnetic polarization in T.
1.5 Remunence Br is the value of magnetic induction or magnetic polarization on the demagneting curve for zero magnetic field intensity.
1.6. The coerciviality of HcB (magnetic induction-related coercivity) is the magnetic field intensity value given by the intersection of the deg curve and line B = 0.
1.7. The coerciality of HcJ (magnetic polarisation) is the magnetic field intensity value given by the intersection of the deg curve and line J = 0.
1.8 The maximum product (BH) max is the maximum value of the product of the corresponding values B and H on the demagneting curve.
2 REQUIREMENTS FOR MEASURING CONTRACTS
2.1. METHOLOGICAL REQUIREMENTS
The measurement assembly shall consist of parts which must meet the following requirements:
(a) the electromagnet specified in 2.2;
(b) measuring coils wound or extended on the sample as specified in paragraph 2.2;
(c) a magnetic induction or magnetic polarization meter integrating voltage induced in measuring coils. The measurement uncertainty of magnetic induction or measurement uncertainty of magnetic polarisation shall not exceed 2%;
(d) the magnetic field intensity gauge (flat measuring coil, magnetic potentialmeter or Hall probe in conjunction with appropriate instruments) shall meet the requirements specified in 2.2 and shall be independently calibrated. The magnetic field measurement error in the sample shall not exceed 2%.
The measurement assembly shall include etalon samples which shall correspond to the magnetic properties and dimensions of samples normally measured by the measurement assembly. These samples shall comply with the relevant requirements of paragraph 2.2.
2.2 TECHNICAL REQUIREMENTS
2.2.1. Construction
2.2.2 Electromagnet
The electromagnet made of magnetically soft material forms together with the sample a closed magnetic circuit. The diagram is shown in Figure 1. The design of the yoke shall be symmetrical; at least one pole attachment shall be movable to minimise the air gap between the sample and the pole attachment. The end surfaces of the two pole attachments shall be as parallel as possible and as perpendicular as possible to the axes of the pole attachments in order to minimise air gaps. For some measurements of yoke and poles can be composed of sheets to reduce slipstream currents. Coerciviality of pole material shall not normally exceed 100 A / m In order to obtain a homogeneous magnetic field in the space holding the sample, the conditions of:
d1 ≥ d2 + 1,2l '(2)
d1 ≥ 2,0l '(3)
where
d1 is the diameter of the cylindrical pole attachment or the smallest dimension of the rectangular pole extension in mm;
l 'is the distance between the pole attachments in mm,
d2 is the maximum diameter of the cylindrical space of the homogeneous magnetic field in mm.
In order to achieve the best potential of the front surfaces of pole attachments during the measurement of the demagneting curve, magnetic induction in pole attachments must be significantly smaller than magnetic polarisation in saturation state. This practically means that magnetic induction must be less than 1 T in iron and in alloys containing between 35% and 50% cobalt less than 1,2 T.
The yoke is magnetised by magnetic coils which must be as symmetrical as possible to the sample. The sample and the magnetic coils shall be coaxial.
Figure 1
If the material standard or the manufacturer does not specify the maximum intensity of the magnetic field at which the measurement is carried out for the sample material, it is recommended that the sample be magnetised to saturation before measuring the demagulation curve. The sample shall be considered to be saturated if the following applies for two baseline magnetic fields H1 and H2:
P2 ≤ P1e0.02454 InH2 / H1, (4)
or
P2 ≤ P1100.02454 log ZVH2 / H1, (5)
and
H2 ≥ 1,2H1, (6)
where
P2 is the maximum reached value (BH) max in J / m3 or HcB in A / m,
P1 is the lower value (BH) max in J / m3 or HcB in A / m,
H2 is the magnetic field intensity value corresponding to P2 in A / m,
H1 is the magnetic field intensity value corresponding to P1 in A / m
In the specific case H2 / H1 = 1,5 from equations (5) and (6) P2 is ≤ 1,01 P1.
The magnetisation process shall in no case cause excessive heating of the sample.
2.2.3 Etalon samples
The ethalon sample shall be of a simple shape (e.g. rectangular cylinder or block). The length of l of the etalon sample shall not be less than 5 mm and its additional dimensions shall be at least 5 mm and shall be such that the sample and sensor of the apparatus shall be within the diameter d2 defined in paragraph 2.2.2.
Etalon samples shall not have surface defects or internal defects.
The end surfaces of the etalon sample shall be as parallel as possible to each other and perpendicular to the axis of the sample in order to reduce as far as possible the air gap between the sample and the pole attachments.
The cross-section of the etalon sample shall be as homogeneous as possible along its length; the differences in cross-section shall be less than 1% of its minimum. The mean cross-sectional value of the etalon sample shall be determined with an uncertainty of less than or equal to 1%.
The magnetic direction shall be indicated on the etalon sample.
Etalon samples belonging to the metering assembly shall cover the range of magnetic characteristics and dimensions of the samples normally measured by the metering assembly.
2.2.4 Measurement set-up
2.2.4.1 Measurement of magnetic induction
The changes in magnetic induction in the sample are determined by integrating the voltage induced in the measuring coil wound or extended to the sample.
The measuring coil shall be wound or applied as close as possible to the sample and shall be symmetrical in relation to the front surfaces of the sample. The connections shall be closely twisted so as not to induce voltage into the loop of the measuring coil.
The difference of magnetic induction in the measurement coil of the latter Bap between two time moments t1 and t2, not corrected for magnetic flux by air, is given by the equation:
IUPAC Name
where
B2 is the magnetic induction in the inside of the measuring coil at the moment of t2 in T,
B1 is the magnetic induction in the inside of the measuring coil at the moment t1 in T,
A is the cross-section area of the sample in m2,
N is the number of turns of the measuring coil,
ITEM 1t2Udt is the integrated induced voltage in the Wb measuring coil over the time interval t2-t1 v.
This difference in magnetic induction of the latter Bap shall be corrected with respect to the magnetic flow of air in the winding of the measuring coil. The difference of magnetic induction from the sample between t2 and t1 is given by the equation:
IUPAC Name
where
μ0 is a magnetic constant equal to 4pi. 10- 7 H / m,
This is the difference in measured magnetic field intensity in A / m,
At least the thread surface of the measuring coil relative to one thread in m2.
2.2.4.2 Measurement of magnetic polarisation
The magnetic polarisation differences in the sample are determined by measuring the integrated voltage induced in the double measuring coil, where only one of these coils is applied. These individual coils must have the same total thread surface and are serially connected in the opposition. The difference of magnetic polarization of the latter in the sample is given by the equation:
EXCIPIENTS J = J2-J1 = 1AN --1t2Udt 9
where
J2 is the magnetic polarization in the sample at the moment of t2 in T,
J1 is the magnetic polarization in the sample at t1 in T,
A is the cross-section area of the sample in m2,
N is the number of turns of the measuring coil surrounding the sample,
IH1t2Udt is an integrated induced voltage in the Wb measuring coil over the time interval t2-t1 in seconds.
The two coils of the double measuring coil shall be within the area of the homogeneous magnetic field defined by equations (2) and (3).
2.2.4.3 Measurement of magnetic field intensity
The magnetic field intensity on the sample surface is identical to the magnetic field intensity inside the sample only where the magnetic field intensity vector is parallel to the sample surface. Therefore, the magnetic field intensity sensor shall be placed as close as possible to the sample and symmetrically in relation to the front surfaces of the sample (see Figure 1).
A flat measuring coil, a magnetic potentialmeter or a Hall probe shall be used to determine the intensity of the magnetic field. The dimensions of the sensor and its location shall be such that there is a limited radius of d2 according to equations (2) and (3) in the area.
The air gap between the sample and the pole attachments shall be minimised to reduce measurement errors.
The front surfaces of pole attachments shall be magnetically equipotent, see equations (3). For some materials of permanent magnets with high remanence, coerciality or both, the magnetic induction value may be higher than 1,0 T or 1,2 T. This can generate an inappropriately high value of magnetic induction in parts of pole attachments adjacent to the sample. In such cases, the front surfaces of pole attachments are not representative areas and larger measurement errors may arise.
2.2.4.4 Determination of the demagneting curve
The deg curve can be obtained or recorded as a B-H or a J-H graph. The transformation of the originally obtained B-signal into a J-signal and vice versa can be done by electrically or numerically subtracting or adding μ0H according to equation (1).
The determination of the B-H curve is described in point 2.2. Determination of the J-H curve is similar, magnetic induction B is confused in corresponding samples and curves by magnetic polarisation J.
Measuring coil used for measuring B or J shall be connected to a calibrated magnetic flow integrator set to zero. The sample is inserted into the measuring coil, clamped into the electromagnets and magnetised into saturation. Magnetic current will be reduced to very low value, zero, or if a reverse polarity is needed to achieve zero magnetic field intensity in the sample. The corresponding value of magnetic induction or magnetic polarisation shall be recorded.
If the current polarity is opposite to the saturation, the current value increases until the magnetic field reaches the coerviality value of HcB or HcJ. The rate of change in magnetic field intensity shall be such as to avoid a phase shift between B and H or the formation of slipstream currents in the sample. For some materials there is a clear time delay between magnetic induction and magnetic field intensity. In such cases, the time constant of the magnetic flow integrator shall be suitably long with a low zero drift to ensure correct integration. The corresponding values H and B or H and J on the demagneting curve shall be obtained either from the continuous writing of the curve by the recorder connected to the output of the device measuring the magnetic field intensity and the magnetic flow integrator, or by measuring the point after the point of intensity of the magnetic field and magnetic induction or magnetic polarisation.
2.2.4.5 Determination of significant points and values of the demagneting curve
Remanence is determined as the value B or J intersection of the deg curve with the B or J axis.
The Coerciality of HcB is determined as the value of: H the intersection of the deg curve with line B = 0, the coerciality of HcJ is determined as the H the intersection of the deg curve with line J = 0.
The maximum product (BH) max is the maximum value of the absolute values of the product corresponding to the values B and H. For example, one of the following methods is determined:
(a) by direct reading or interpolation from a set of curves B.H = the constant to which the deg curve is recorded;
(b) by quantifying the products of B.H for the amount of points of the demagneting curve and ensuring that the maximum value is included;
(c) multiplying B and H electronically and recording this product as function B or H;
(d) by the geometric detection of such a point (B, H) of the demagneting curve at which the tangent to the demagneting curve is parallel to the intersection of the points (B, 0) and (0, H) and the quantification of this product B.H.
2.2.4.6 Determination of external conditions
Measurements shall be made at an ambient temperature of 18 ° C to 28 ° C. The temperature of the sample shall be measured by a non-magnetic temperature sensor attached to the electromagnets' pole attachments. Temperature dependence of measuring instruments (e.g. Hall Probe) shall be included in the calculations and evaluation.
2.2.5. Labels and marks
2.2.5.1 Measurement set-up
The special inscriptions and marks on the measurement assembly outside the normal marking shall be replaced by a technical document which shall be drawn up and shall include:
(a) a list of all measuring instruments and equipment belonging to the measurement assembly, indicating the manufacturers and production numbers and, where appropriate, the errors of measuring instruments and measuring kits as specified by the manufacturer;
(b) a detailed and clear diagram of the connection for the relevant type of measurement, technical descriptions and instructions for operation of the components of the measurement assembly;
(c) concise descriptions of measurement and supply methods (e.g. magnetic field measurement, control computer usage);
(d) the lower and upper limits of the ranges in which the measurement assembly will be used;
(e) impedance of important components and gauges;
(f) a list of etalon samples;
(g) calibration or verification sheets of measuring instruments which are part of the measurement assembly, if calibration or verification has been carried out;
(h) the verification sheet of the measurement set-up (for subsequent verification);
(i) a record of all measurements with etalon samples relating to the measurement assembly.
2.2.5.2 Etalon samples
The ethon sample shall bear the registration number or letters on the sample in the same, permanent and indelible manner. The marking shall not be on the front surfaces of the sample.
Each etalon sample shall be accompanied by a record sheet indicating:
(a) the registration of the ethalon sample;
(b) the type and type of material;
(c) cross-section of the sample,
(d) the shape and dimensions of the sample.
If all the data to be included in the record sheet are included in the sample calibration sheet, the etalon sample may not have a record sheet.
3 TYPE APPROVAL
3.1. Type-approval procedure
3.1.1 Preliminary assessment
The evaluating authority shall, on the basis of the examination of the documents1) ascertain whether the documentation and then the measurement assembly meet the requirements laid down in this Decree, decide on the continuation of the tests or submit a proposal for negative termination of the tests.
3.1.2. Preliminary test by measuring material samples
3.1.2.1. The applicant shall deliver at least 2 pieces of etalon samples of material belonging to the test set to the assessor. Etalon samples shall cover their mass and their magnetic properties the mass range and the magnetic properties of the ethalon samples as measured by the test set within the type test range. These etalon samples shall comply with the requirements of paragraphs 2.2.3 and 2.2.5.2. The applicant's etalon samples shall be accompanied by copies of the sample registers, where appropriate, of the previous sample calibration sheets. The samples delivered shall be accompanied by the results and reports of their measurements by a test set in the range of tests carried out not more than 3 months before the date of delivery.
3.1.2.2. In the case of delivered etalon samples, measurements shall be made on the etalon measurement assembly of the assessment body of the demagneting curve according to paragraph 2.2. A calibration sheet shall be drawn up for the measured sample, indicating the arithmetic mean of the repeated measurements.
3.1.2.3. The relative differences between the measurement of the emission curve B- H of the etalon samples (related to the test set) by the test set and the etalon measurement set in% shall be calculated as the minimum standard distance of the ith point (Bi, Hi) characteristics determined by measurement of the measured measurement set from the characteristic determined by measurement of the same etalon sample by the etalon measurement set according to the equation (10), (11) or (12):
δai = δBi.100 / --1 + Hi / Bi.dB / dHi2 =
= ЦBi.100 / --Bi2 + Hi.dB / dHi2 10
δai = δHi.100 / --1 + Bi / Hi.dB / dHi-12 =
> TABLE >
δai = δBi.δHi.100 / --δBi2 + δHi2 =
♪ ♪
where the square roots are taken only positive and where
δBi = Bi-Bi '/ Bi = iBi / Bi, 13
IUPAC Name
δHi = Hi- Hi '/ Hi = ШHi / Hi, 15
- Hi, 16.
(dB / dH) i is the slope of the tangent curve given by measuring the etalon sample by the etalon measurement set at the point (Hi, Bi '),
Hi and Bi are the intensity values of the magnetic field or the magnetic induction of the ith point are the characteristics of the etalon sample as measured by the measured measurement set,
Bi 'is the magnetic induction value subtracted from the characteristic measured by the etalon measurement set for the Hi value,
Hi 'is the magnetic field intensity value subtracted from the characteristics measured by the etalon measurement set for the Bi value.
If the position of the demagulation curve B-H is measured, the procedure is similar, the relative differences of δai are calculated according to equations (10) to (16), where the B mark is always replaced by the J mark, i.e. the magnetic induction B is always replaced by the corresponding magnetic polarisation value J.
The relative differences between the measurement of the demagneting curve B-H or the demagneting curve J-H δai shall be less than 4% for all points of measurement of the demagneting curve of the etalon samples within this test.
3.1.3. Inspection of the test metering assembly
The external inspection and inspection of the prescribed technical documentation shall take place at the point of use of the test metering assembly. The external inspection shall check:
(a) the measuring assembly shall not be mechanically damaged;
(b) the measurement assembly shall consist of measuring instruments, etalons and components specified in the documentation;
(c) the arrangement of measuring instruments and components shall be in accordance with the wiring diagram for the relevant type of measurement;
(d) the completeness of all documents required under point 2.2.5.1.
Test by measuring samples of materials
The measurement of the samples shall be carried out by measuring the etalon samples (belonging to the etalon metering assembly) of the testing metrological authority in its presence by the test metering set in accordance with paragraph 3.1.2.
Preparation of the technical test report
The technical test report shall contain a description and results of the tests carried out in accordance with paragraphs 3.1.2, 3.1.3 and 3.1.4, which shall have a positive result. It also contains descriptions, drawings and diagrams necessary to identify the type and clarify its function.
Approval certificate
The particulars of the type-approval certificate shall be laid down in a separate legislative act (2).
4. VERIFICATION
Initial and subsequent verification shall consist of tests according to paragraphs 3.1.2, 3.1.3 and 3.1.4. If the result of all these tests is positive and the measurement assembly complies with the requirements laid down in this Regulation, a verification sheet shall be issued and the test set-up shall be provided with an official mark. 3)
1) Paragraph 1 (2) of Decree No. 262 / 2000 Coll., which ensures consistency and accuracy of measuring and measuring instruments, as amended by Decree No. 344 / 2002 Coll.
2) § 3 of Decree No. 262 / 2000 Coll.
3) § 6 of Decree No. 262 / 2000 Coll.
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Regulation Information
| Citation | Decree No. 72 / 2004 Coll., laying down requirements for measurement kits for the measurement of magnetic characteristics |
|---|---|
| Regulation Type | - |
| Author | - |
| Collection | Code of Laws |
| Date of Promulgation | 24.02.2004 |
|---|---|
| Effective from | 01.03.2004 |
| Effective until | - |
| Status | Valid |
The regulation text is for informational purposes only.
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