Because the magnetic field to the human eye is transparent, can not see cannot touch. So measuring their strength requires special tools to measure the working state of the magnetic circuit. Currently there are two commonly used tools, one is gauss meter, the other is the use of tensile testing equipment.
A gauss meter is an electronic device that measures the flux density at any given point on a magnet. When a single probe touches the surface of a magnet, it induces flux density and converts it into a voltage read by a gauss meter. Gauss readings are displayed on the meter. The maximum value is found when moving on the surface of the magnet (usually at the magnetic pole). This value is the maximum gaussian number of the magnet.
Advantages: very intuitive, in the same environment, gauss value is very accurate.
Cons: in the real world, gauss testing has serious limitations. The gaussian profile varies significantly according to the position and Angle of the probe placed in the working area relative to the flux travel line. Because the magnetic circuit changes from one magnet to the next, and because of "human error", accurate readings are difficult to obtain, manual gauss values do not determine the strength of the magnet. Simply applying different pressures on the probe to the surface of the magnet results in significant changes. Because of the length of time between tests, different people take different paths to the test, which further affects accuracy. Finally, any mechanical damage to the probe or cable will reduce the accuracy of the instrument. In particular, the probe is basically "consumable" and needs to be replaced regularly. These factors add to time, cost and labor costs.
The tension test kit USES compact digital scale or spring scale, and a series of black test fixture. The separation force is determined by measuring the magnetic pull force using a calibrated scale and an iron specimen, usually in pounds or ounces. One end of the test fixture is connected to the ruler and the other end is firmly connected to the working area of the magnet in the predetermined position. It then slowly pulls apart in a direction perpendicular to the magnet until it is released. Tensile strength is recorded on scale.
The digital scale provided in the tensile test kit is also a scientific device that can be calibrated. In practice, the pull test method is also convenient because the test equipment is cheaper to acquire, more efficient to operate, and more consistent repeatable values than the gaussian method, regardless of operator. Each time the test is repeated, the iron test fixture is attracted to the peak energy point of the magnet, and the gaussian method requires the operator to use the probe to find the peak energy point in the working area. Tensile testing is also more effective than gaussian method in minimizing downtime.
As gauss instrumentation has evolved over the years, so has the mechanical tension test suite. Some companies' tensile test kits still offer simple spring-type gauges. The fatigue degree of the spring will cause errors in the test.