BS EN 60404-15:2012 pdf download

BS EN 60404-15:2012 pdf download.Magnetic materials Part 15: Methods for the determination of the relative magnetic permeability offeebly magnetic materials.
AH is the relative correction of the magnetic field strength and Nm is the magnetometric self-demagnetization factor
This Is discussed In more detail in Annex A.
4.3.4 Flux Integrator, The flux integrator shall be an electronic charge integrator or similar device, calibrated with an uncertainty of ± 0,5 % or better.
4.3.5 Current measuring device. The current measuring device shall consist of a calibrated resistor connected in series with the magnetizing circuit and a calibrated digital voltmeter.
The magnetizing current shall be determined from the measurement of the voltage developed across the resistor. The combined uncertainties of the resistor and voltmeter shall be such that the magnetizing current can be determined with an uncertainty of ± 0.2 $ or better Alternatively, an ammeter calibrated with an equivalent uncertainty can be used.
4.3,5 Micrometer. The micrometer for measuring the transverse dimensions of the test specimen for the solenoid method shall be calibrated. For the magnetic moment method, the volume is required and appropriate dimensional measurements shall be made.
4.4 Test specimen for the solenoid method
The test specimen shall consist of a round or rectangular bar, or a number of strips or wires having a total cross-sectional area of at least 100 mm2. The maximum cross-sectional area shall be determined by the diameter of the central aperture of the search coil. Allowance shall be made for the easy insertion and withdrawal of the test specimen without disturbing the position of the search coil.
To avoid significant errors introduced by self-demagnetization, the length to equivalent diameter ratio of the test specimen shall be not less than 10:1 When corrections for self- demagnetization are required see Annex A.
For example. values are given in Table 3 for a rod of circular cross section with an aspect ratio of 10:1, a diameter of 30 mm and a search coil with an effective average diameter of 52,2 mm. The relative corrections to the applied magnetic field strength and the magnetic polarization for different relative magnetic permeabilities due to self-demagnetization are shown.
The magnetizing current to produce the required magnetic field strength shall be calculated from the magnetic field strength to current ratio previously determined for the solenoid (see
4.3,1).
At low values of magnetic field strength, the eartWs magnetic field may be significant It is recommended that the axis of the solenoid is aligned in a horizontal plane in a direction normal to the horizontal component of the eartWs magnetic field.
The magnetic polarization shall be measured by inserting the demagnetized test specimen into the search coil or moment detection coil, adjust the magnetizing current to the required value taking care not to overshoot, zero the flux integrator, withdraw the test specimen and record the integrator reading Care shall be taken to withdraw the test specimen from the search Coil or moment detection coil to a position where it no longer has an influence on the search coil or moment detection coil, as indicated by the integrator reading.
For the solenoid method, the complete measurement procedure shall be repeated with the other end of the test specimen Inserted Into the search coil. Either the two integrator readings shall be averaged or used separately, depending on the customer’s requirement.
The procedure Is repeated as necessary to determine the given measurement repeatability.
NOTE Smaii fluctuations of the magrwtiling current or of the ambient magnetic fi.td can nduc• large nstabililiei in the measured Itux, To avoid this, a compensation coil can be used.
The weight of the specimen can change the direction of the search coil axis used in the solenoid method by a small amount during the withdrawal of the specimen, which leads to an additional induced voltage in the search Coil. theretore the search coil should be fixed very rigidty or mechanically decoupled from the movement of the specimen.
Electrostatic charging of the search coil or moment coil during the withdrawal of the specimen can disturb the flux measurements and should be prevented. A copper shielding might be effective to avoid signal contributions from electrostatic charges.
4.6 CalculatIon
For the solenoid method, the magnetic polarization shall be calculated using equation (4).