Magnetic-field strength refers to the amount of magnetism that a given magnet can attract and hold. This is a crucial feature to consider when choosing a magnetic product for any application.
Measuring the strength of a magnet is done in several different ways, depending on the needs of the application. Some of the most common measurements include:
gauss and tesla (10,000 gauss equals one tesla)
A gauss is an SI unit that measures the magnetic flux density produced by a magnet. This is calculated by dividing the total electromotive force in volts per second at right angles to the direction of the magnetic field by the area of a wire carrying that current.
It is also possible to measure a magnet’s remanence in gauss by using a gauss meter or hall probe. This remanence value is then multiplied by the coercivity of the magnet, to determine its maximum energy product.
Another commonly used measurement for a magnet’s strength is its pull force, which is measured in kilograms and newtons. This is the force required to pull a magnet away from a flat metal surface when making full surface-to-surface contact with that metal. The grade of the metal, surface condition and angle of pull have all an impact on the pulling power of a magnet.
Mega gauss oersteds (MGOe)
Magnet grades are determined by the combination of gauss and Oersted measurement results, which are often given in units of mega gauss oersteds. For example, a magnet with a remanence of 1 gauss and coercivity of 1.7 MGOe is considered a high-grade magnet.
A pull-gap tester is a machine that can test the pull strength of a magnet. It tests a magnet over a range of air gaps and plots the results on a hysteresis graph.
Open circuit flux densities of neodymium magnets rarely exceed 6,000 gauss. This is due to the fact that neodymium magnets have a straight line demagnetisation curve.
Pull-gap and open circuit tests are often performed on the same magnet as a remanence or coercivity measurement. This is to ensure that the remanence and coercivity values are comparable.