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# How can we calculate the magnetic field strength of a magnet?

- The intensity of the magnetic fields can be investigated by means of different formulas that can be found in the following text.

Magnet users still face the problem of being able to verify the quality and magnetic properties. Most users cannot determine the value of the parameters of the main magnet themselves.

That's the reason ImagnetShop lets users know how to determine magnetic field strengths. In this case, the most appropriate is a relative measurement, with which the characteristic properties are determined. In this measurement of the characteristic properties, the **magnetic field** strength, the magnetic flux and the momentum initiated by the magnet are determined. **Magnetic flux** and magnetic momentum tests require different test coils with different specifications. Therefore, the magnetic field strength is the most common test method used.

**How is the magnetic field strength calculated?**

The magnetic field strength for a magnet shall be calculated in a simple way as follows. For cylindrical bodies:

B (X) = Br / 2 * [(L + X) / (sqrt (R ^ 2 + (L + X) ^ 2) - (X / (sqrt (R ^ 2 + X ^ 2) )))]

For cuboids or cubic bodies we use:

B (X) = Br / Pi * [(A * B) / (arctane (2 * X * sqrt (4X ^ 2 + A ^ 2 + B ^ 2))) - [ (A * B) / (arctano (2 * (L + X) * (sqrt (4 * (L + X) ^ 2) + A ^ 2 + B ^ 2))]

For hollow cylindrical bodies:

B (X) = Br / 2 * [((L + X) / (sqrt (R ^ 2 + (L + X) ^ 2)) - ((L + X) / (sqrt () r ^ 2 + (L + X) ^ 2))) - ((X / sqrt (R ^ 2 + X ^ 2) - (X / sqrt (r ^ 2 + X ^ 2))]

Br in the formula represents the resultant induction; X represents the air space between the magnetic surface and the testing point.

When observing the above equation, the dimension, the test position and the quality of the magnet all affect the value of the magnetic field strength. When measuring, it should be noted that, due to the protection effect against ferromagnetism and nickel coating, the measured value of the magnetic field strength is below the theoretically set value.

With multipolar magnetization and complex conditions, the developer determines the distribution and strength of the magnetic field. For this purpose, FEM or FEA (finite element analysis) software is used. The determined distribution and force of the magnetization state and the flow distribution of the entire magnetic circuit system is calculated precisely.

**Which instruments can be used to measure the magnetic field strength?**

The intensity of the magnetic field can be measured with a **gauss meter** or a Tesla meter. Many magnetic users now have their own gauss meters and also establish acceptance criteria for magnetic field strength. With a multipolar magnet, the magnetic field strength is measured with the magnetic analyser.

**Where can I buy the best gauss meters?**

You can obtain a professional tool, the gauss meter IMA GS20. This is a specific device to measure and control the density of the magnetic field. As a result, the measurement tool is relatively universal. The device has a digital display and is suitable for measuring DC or AC flux densities. The device is relatively simple and practical, with functions such as storing the maximum value, it offers very useful features. You can switch the display unit between mT and G on the display. The measuring range reaches up to 200 MT. The device is powered by a 9V battery. The operating time is approximately 20 hours.