BS EN IEC 60404-7 pdf free download

BS EN IEC 60404-7 pdf free download.Magnetic materials.
4 Principle of the method If a magnetic test specimen is placed in a uniform and unidirectional magnetic field then it will distort this magnetic field unless a condition that no flux (additional to that previously carried by the air space it now occupies) enters or emerges from the test specimen. This condition represents a state of complete demagnetization which occurs when a demagnetizing coercive magnetic field strength is applied to the test specimen such that the magnetic polarization is zero [2]. The test specimen is magnetized to saturation (Js) and then the magnetic field is reduced smoothly without interruption to zero (J,). Afterwards the polarity of the magnetic field is reversed and a demagnetizing field is increased until the magnetic polarization of the test specimen is zero. The applied magnetic field strength required to achieve this condition is measured and defined as the coercivity HcJ of the test specimen (see Figure 1). A magnetic flux sensing probe enables the detection of the condition of no distortion of a uniform magnetic field by the test specimen and provides the means for determining the coercivity. For this measurement, the test specimen and the magnetic flux sensing probes are placed in an open magnetic circuit in the uniform and unidirectional magnetic field of a solenoid. The flux sensing probe should be placed as follows: a) inside the solenoid, close to the end of the test specimen (Method A一Hall probe, see Figure 3), or b) inside the solenoid, at a distance from the test specimen, depending on the size and permeability of the test specimen (Method A一differential fluxgate probe, see Figure 4), or c) outside the solenoid (Method B – differential fluxgate probe, see Figure 5). The solenoid and measuring equipment shall be connected as shown in Figure 2. NOTE There is an alternative way to use an axially vibrating search coil as magnetic sensing probe like Method A [3].5 Test specimen
The shape and the dimensions of the test specimen may be varied provided that they meet the following conditions:
a) the test specimen can be placed inside the solenoid so that its major axis is coincident with the axis of the solenoid;
b) the test specimen can be magnetized to saturation.
NOTE For the effects of shape and non-uniform magnetic properties of the test specimen refer to 9.2.2 and 9.3.
6 Solenoid
The magnetic field in the solenoid shall have the following specifications:
a) the magnetic field strength in the solenoid over the volume of the test specimen shall not vary by more than ±0,5 %;
b) an AC ripple of the magnetic field strength in the solenoid shall be less than ±0,5 % of the magnetic field strength.
7 Compensation for the earth’s magnetic field and static and dynamic magnetic noise fields
The measurement of the coercivity of a test specimen of soft magnetic material can be distorted by the earth’s magnetic field and by external static and dynamic magnetic noise fields. Compensation for these can be achieved either by:
a) a suitable compensation system for the earth’s magnetic field [4] or a magnetic shield placed around the measurement region, or
b) the magnetic flux sensing probe for the measurement of the stray magnetic field of the test specimen is a differential fluxgate probe to suppress an influence of these uniform external magnetic fields (see Figures 4 and 5).BS EN IEC 60404-7 pdf download.