JJF 1832-2020 PDF English
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Calibration Specification of (1mT~2.5T) Magnetometers
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JJF 1832-2020: Calibration Specification of (1mT~2.5T) Magnetometers---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/JJF1832-2020
JJF
NATIONAL METROLOGY TECHNICAL SPECIFICATION
Calibration Specification for (1 mT~2.5 T) Magnetometers
Issued on: JANUARY 17, 2020
Implemented on: APRIL 17, 2020
Issued by. State Administration for Market Regulation
Table of Contents
Introduction... 5
1 Scope... 6
2 References... 6
3 Terms and units of measurement... 6
3.1 magnetometer... 6
3.2 zero drift... 6
3.3 basic range... 6
4 General... 6
5 Metering characteristics... 8
5.1 Magnetic flux density indication error... 8
5.2 Difference between the forward and reverse indications of the probe... 8
5.3 Zero drift... 8
5.4 Up and down variation... 8
6 Calibration conditions... 8
6.1 Environmental conditions... 8
6.2 Measurement standards and other equipment... 8
7 Calibration items and calibration methods... 10
7.1 Calibration items... 10
7.2 Calibration methods... 10
8 Expression of calibration results... 16
9 Recalibration interval... 18
Appendix A Influence of the angle between the Hall plate and the magnetic field on the
measurement results... 19
Appendix B Example of evaluating the measurement uncertainty of the indication error
of magnetic flux density... 21
Appendix C Magnetometer calibration raw record format... 26
Appendix D Calibration certificate inner page format... 28
Calibration Specification for (1 mT~2.5 T) Magnetometers
1 Scope
This Specification applies to the calibration of 1 mT ~ 2.5 T DC magnetic field
magnetometers, and also to the calibration of the DC magnetic field measurement part
of multifunctional magnetometers.
2 References
The following documents are referred to in this Specification.
JJF 1013-1989 Terms in common use and their definitions for the magnetic metrology
For dated references, only the dated version applies to this Specification; for undated
references, the latest version (including all amendments) applies to this Specification.
3 Terms and units of measurement
3.1 magnetometer
An instrument used for measuring magnetic field strength or magnetic flux density
(magnetic induction intensity).
3.2 zero drift
The amount by which the magnetometer reading deviates from zero when the probe is
placed in a zero magnetic field cavity.
3.3 basic range
The measuring range with the best maximum permissible error of magnetic flux density.
4 General
A magnetometer is an instrument used to measure the magnetic flux density (magnetic
induction intensity) of an object at a point in space, among which the Hall effect
magnetometer is the most typical. Magnetometers are divided into digital
magnetometers and pointer magnetometers according to the display mode. Their
principle structure block diagrams are shown in Figure 1 and Figure 2, respectively.
Magnetometer probes are divided into radial probes and axial probes according to the
direction of the measured magnetic field.
5 Metering characteristics
5.1 Magnetic flux density indication error
The maximum allowable error generally does not exceed ± (0.02% ~ 10%).
5.2 Difference between the forward and reverse indications of the probe
The difference between the forward and reverse indications of the magnetometer probe
generally does not exceed its maximum allowable error.
5.3 Zero drift
In the zero magnetic field cavity, the zero drift of the magnetometer generally does not
exceed 1/3 of its maximum allowable error.
5.4 Up and down variation
The up and down variation of a pointer magnetometer generally does not exceed the
error coefficient value related to its range value.
Note. The above indicators are not applicable to qualification judgment and are for
reference only.
6 Calibration conditions
6.1 Environmental conditions
When calibrating the magnetometer, the environmental conditions shall meet the
requirements of Table 1.
6.2 Measurement standards and other equipment
The magnetometer calibration device consists of a zero magnetic field cavity, a
magnetic field coil (Helmholtz coil, solenoid, etc.), an electromagnet, an excitation
power supply, a DC ammeter, a probe position adjustment device, a standard
magnetometer (or a magnetometer standard table), etc. The calibration device must be
verified (or calibrated) against a higher-level measurement standard, and its combined
standard uncertainty must not exceed 1/3 of the maximum allowable error of the
calibrated magnetometer.
6.2.1 Zero magnetic field cavity
The magnetic flux density in the zero magnetic field cavity is no more than 1×10-6 T.
6.2.2 Magnetic field coil
When the magnetic flux density of the magnetic field is in the range of 1 mT ~ 100 mT,
the magnetic field generator can use a magnetic field coil. The magnetic field coil can
be a Helmholtz coil, a solenoid coil, or the like. In the uniform area of the coil magnetic
field, the error caused by the magnetic field uniformity shall be no more than 1/5 of the
absolute value of the maximum allowable error of the calibrated magnetometer, and the
error introduced by the coil constant shall be no more than 1/5 of the absolute value of
the maximum allowable error of the calibrated magnetometer.
6.2.3 Electromagnet
When the magnetic flux density of the magnetic field is in the range of 10 mT ~ 2.5 T,
the magnetic field generator can be an electromagnet. The pole surfaces of the
electromagnet shall be flat and the two pole surfaces shall be parallel. In the
electromagnetic field homogeneity region, the error caused by the magnetic field
homogeneity shall be no more than 1/5 of the absolute value of the maximum allowable
error of the calibrated magnetometer.
6.2.4 Excitation power supply
The change in the excitation power supply current within 60 s shall not exceed 1/5 of
the absolute value of the maximum allowable error of the calibrated magnetometer.
6.2.5 DC ammeter
The DC ammeter can be integrated into the excitation power supply or placed separately
to measure the excitation current of the magnetic field coil. The error shall not exceed
1/5 of the absolute value of the maximum allowable error of the calibrated
magnetometer.
6.2.6 Probe position adjustment system
The probe position adjustment system can adjust the spatial position of the standard
magnetometer probe and the calibrated magnetometer probe, and has the function of
probe direction rotation to ensure that the probe Hall plate is perpendicular to the
magnetic field direction. The error caused by adjusting the probe position and direction
shall not exceed 1/5 of the absolute value of the maximum allowable error of the
calibrated magnetometer.
6.2.7 Standard magnetometer
The standard magnetometer may be a nuclear magnetic resonance magnetometer, a Hall
effect magnetometer, or the like. The allowable error shall not exceed 1/3 of the absolute
value of the maximum allowable error of the calibrated magnetometer, and the error
change within one year shall not exceed its maximum allowable error.
7 Calibration items and calibration methods
7.1 Calibration items
The calibration items are shown in Table 2.
7.2 Calibration methods
7.2.1 Appearance and power-on inspection
7.2.1.1 The housing, exposed switches, function buttons and corresponding markings
of newly produced magnetometers shall be intact; magnetometers in use and after repair
shall not have damage or defects that affect normal operation.
7.2.1.2 The product name and model, manufacturer name, factory serial number, etc. of
the magnetometer shall be clearly marked.
7.2.1.3 The accessories of the magnetometer shall be complete. The probe and
magnetometer shall be matched and their instruction manuals shall be provided.
7.2.1.4 The connection wires of the magnetometer shall not be loose; the switches and
buttons shall function normally; it shall be able to work normally after power is turned
on.
7.2.2 Zero drift
7.2.2.1 Preheat the magnetometer to be calibrated according to its instructions.
7.2.2.2 Place the magnetometer probe to be calibrated in the zero magnetic field cavity
and adjust its range to the lowest range.
7.2.2.3 Zero the calibrated magnetometer and select a recording time based on the
requirements (if no requirements are available, 60 seconds may be selected). Record
the maximum value (Bmax) and minimum value (Bmin) of the readings within this time.
The zero drift is calculated according to Formula (2).
Where.
Bp – zero drift of the calibrated magnetometer, T;
Bmax – maximum value of magnetometer reading, T;
Bmin – minimum value of magnetometer reading, T.
7.2.3 Magnetic flux density indication error
7.2.3.1 Selection of calibration points
Select the calibration points according to the usage requirements. If there is no
requirement, select by referring to the following method.
-- Pointer type magnetometer. For basic range, select points with digital
graduation lines within the measuring range as calibration points, and the
number of calibration points shall be no less than 3 points. For non-basic range,
select two points as calibration points. the maximum point of basic range error
and the upper limit point.
-- Digital type magnetometer. The basic range can select (but not limited to) the
upper limit of the range, 80% range point, 60% range point, 40% range point,
and 20% range point as calibration points; for non-basic range, generally
select 3 points.
The indication error of the magnetic flux density value of the calibrated magnetometer
is calculated according to Formula (3).
Where.
Ex – indication error of magnetic flux density of the calibrated magnetometer;
Bx – indication value of the calibrated magnetometer;
Bs – magnetic field flux density reference value (standard value).
7.2.3.2 Magnetic field generator
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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