demagnetisation BH curve
The BH curve shows the dependence of magnetic induction B, or polarisation J, on the intensity of the demagnetising magnetic field H in the second quadrant.
demagnetisation BH curve
The basic magnetic properties of permanent magnets read out of the demagnetisation BH curve include, among others, remanent induction Br, HcB coercivity, internal HcJ coercivity , and BHmax energy product. Our accredited laboratory performs measurements of the demagnetisation BH curve for all the current commercial types of permanent magnets:
parameters of the demagnetisation BH curve
Remanent Br induction –residual magnetic induction in the magnet at the zero intensity of the magnetic field after the magnet has been saturated; it is determined in the graph as the intersection point of the hysteresis loop and coordinate axis B, equals the magnetic polarisation in this point.
HcB coercivity– magnetic field intensity at which the zero magnetic induction was reached after the magnet has been saturated; it is determined in the graph as the intersection point of hysteresis loop B(H) and coordinate axis H in the 2nd quadrant.
HcJ coercivity – magnetic field intensity in the magnet at which zero magnetic polarisation is reached after the magnet has been saturated; it is determined in the graph as the intersection point of hysteresis loop J(H) and coordinate axis H in the 2nd quadrant.
BHmax energy product – the maximum value of BH product along the demagnetisation curve;; the maximum product equals double the energy density (volume unit energy) of the magnetic field in the magnet and corresponds to the largest rectangle under the BH curve in the graph.
capabilities of our testing laboratory
The given parameters of permanent magnets can be measured by means of a hysteresisgraph, pulse magnetometer, or other alternative methods. Our laboratories are equipped with a hysteresisgraph (accredited laboratory pursuant to ISO 17025) – standardised method pursuant to IEC 60404-5 or ASTM A977/A977M, as well as a pulse magnetometer pursuant to IEC TR 62331 which makes it possible to measure internal HcJ coercivity on all types of permanent magnets, even SmCo (samarium-cobalt) magnets, where this parameter cannot be measured by means of hysteresisgraph at a room temperature. Our state-of-the-art equipment also makes it possible to measure these parameters of standard and complex magnet shapes in the temperature range of -40°C to +220°C. When measuring the BH characteristics using the pulse method, we achieve a magnetic field with induction up to 7T! However, neither the hysteresisgraph nor pulse magnetometers make it possible to measure all shapes, sizes and use all methods of magnetising permanent magnets. The magnets with shapes and sizes too large or too small to be measured by means of the hysteresisgraph or pulse magnetometer are to be replaced with „standard samples“ manufactured from the same production batch, and these serve as a representative of the magnet material.
we measure in an accredited laboratory
- magnetic material properties specified in the specification
- magnetic material properties at working temperature
Jan Kratochvil ml.
