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Measuring Magnetic Field Strength of Neodymium Magnets Using a Gaussmeter

Posted on July 27, 2017

Neodymium magnets are the strongest available magnet material with remanence (Br) between 10.5 and 14.8 kilo-Gauss. Samarium Cobalt magnets have Br values between 8.5 and 11.0 kilo-Gauss, and 2.3-3.85 kilo-Gauss for Ceramic magnets. The Earth's magnetism (depending on the location) is around half of a Gauss. So how do you verify these values?

To measure the exact strength and direction of magnetic field, the most accurate tool to use is a hand-held device called gaussmeter, or known as a magnetometer or an electromagnetic field detector or pull tester. They can be purchased at many industrial shopping outlets and priced starting from $400 to more than $1000 depending on the complexity of their functionality.

Before initial measurement, first selecting the maximum voltage at 10 volts DC far away from any magnet material. You’d want to set your baseline voltage with no interference by surrounding magnetic fields. Away from any magnetic field, the voltage reading should be 0. Touch the meter’s Hall sensor (through which an electrical current is passed) to one of the two magnet’s poles and record the reading shown on the meter. If the voltage rises, it is the south pole touching the Hall sensor; vice versa, if the value drops, it is the north pole. Gauss value is simply the voltage difference divide by sensitivity setting. Make sure the units are converted and matched to correctly calculate the remanence. The value is the magnetic field strength at the magnet’s pole surface. You can repeat the same procedure to find the field strengths at corresponding distance away from the magnet material. Large magnetic field strength can also be represented in Tesla which is equivalent to 10,000 Gauss.

This tool and method is especially useful and accurate when an air freight is required for international orders on strong rare earth Neodymium magnets to ensure there is no strong magnetic field interfering the aircraft’s GPS system. Theoretically the Gauss value decreases roughly by the square of the distance increase at the magnet poles, and by the cube of the distance increase at the magnet center point. Besides the distance, magnet sizes and surround temperature affect the magnet’s strength as well. For accurate readings, makes sure you’re measuring far away from other magnetic products. For any magnet material or their material grades, it is difficult to manufacture the exact targeted value, and instead we aim for a specific range during our process. It is almost impossible to homogenize the initial material for Neodymium magnets, so any micro-sized variation can yield a magnetic field strength difference. It is noted that Gauss meters measuring magnetic fields at equal or less than 60 Hz AC frequencies should only be used for home appliances and not suitable for measuring magnets.