Measuring magnetic properties
The key parameters for permanent magnets are remanence, coercive field strength and maximum energy product. In practice, these values are often needed to compare batches, verify suppliers or assess whether thermal exposure has shifted the usable operating window.
Permanent magnets generate a constant magnetic field without the need for electricity. They are made from hard-magnetic materials such as iron alloys, cobalt, nickel or ferrites and always have a north and a south pole that attract or repel depending on their orientation.
Remanence is the magnetisation remaining after the external field is removed. Coercive field strength is the field required to demagnetise a magnet. The maximum energy product indicates the magnetic performance of a permanent magnet. Typical applications include motors, generators, speakers, sensors and switches, allowing compact and efficient device designs based on electromagnetic induction.
*accredited testing per ISO/IEC 17025
"Demagnetisation curve and magnetic moment measurements are carried out in the accredited TW Network lab."
Remanence is determined using a hysteresis graph and indicates how much magnetisation remains after magnetisation. Coercive field strength defines the resistance against demagnetisation and is derived from the BH curve. Typical values range from 740–1200 mT for remanence and up to 960 kA/m for coercivity, depending on the magnet material. Together, these values help confirm whether a magnet still fits the intended application window.
What is the maximum energy product of a magnet?
The maximum energy product ((BH)max) is derived from the demagnetisation curve. It shows how much energy can be stored in a magnet and is decisive for applications where compact dimensions and strong fields are required. Depending on the magnet class, values between 140 and 440 kJ/m³ are typical.
What does the BH demagnetisation curve show?
The BH curve plots magnetic flux density (B) against magnetic field (H) and visualises magnetisation and demagnetisation behaviour. The second quadrant of the hysteresis loop is particularly important because it shows the working point under load. Continuous measurement of the curve reveals how temperature, ageing or machining affect magnetic performance.
How is magnetic moment determined?
The magnetic moment describes the strength of a magnet and is measured in ampere square metres. It is determined via torque methods or using fluxmeter systems. Knowing the magnetic moment helps when calibrating magnetic assemblies or compensating tolerances.
How is magnetic flux density measured?
Magnetic flux density (B) indicates the magnetic field within or around a permanent magnet. It is measured in tesla and depends on material, geometry and magnetisation. Flux density measurements use Hall sensors, fluxmeters or search coils and are essential for verifying design targets.
Contact us for more information on measuring and analysing magnetic flux density.
How is the magnetisation angle measured and why does it matter?
The magnetisation angle of a permanent magnet describes the orientation of magnetisation. Accuracy (angle error) is critical when the magnet position is tracked by Hall sensors or relays. Even a small deviation from the geometric axis can lead to delays, malfunctions or failures.
Deviations often originate during manufacturing. When pressing magnet blocks within a magnetic field, alignment between pressing direction and field cannot always be ensured.
When cutting magnets from the block, misalignment can occur if the block is clamped incorrectly. To guarantee functionality we use dedicated equipment that measures angular deviation of the magnetisation direction from the geometric axis by evaluating flux vectors at defined distances. The method currently applies to bipolar magnets.
Contact us for further details on our magnetisation angle services.
