Magnet Strength - What about Gauss
All Magnets are not equal
Most manufacturers of permanent magnets use the term "gauss
rating" to characterize their products. however, this term is misleading since
"gauss rating" characterizes the core of the magnet but not the magnetic
field on the surface of the magnet.
There are two types of magnets. "Bipolar" magnets have
repeatable north/south polarity on the same side of the magnet. These magnets are
usually thin and flexible. "Unipolar" is a term used to distinguish the
other category of magnets that are usually "unidirectionally" applied to the
body. The two magnetic poles are located on different sides of the magnet - the south
pole on one side and the north pole on the other. By having both poles on different
sides, one may better exploit the basic laws of physics and assure a greater depth of
penetration ... generally 4-8 times larger than bipolar magnets.
The chart below shows the dramatic difference in the depth of
penetration between "bipolar" and "unipolar" magnets, as measured by
the MSM-7 instrument (patent applied for). While the maximum depth of penetration of
"bipolar" magnets is approximately 1.25 inches, the magnetic fields generated by
Tectonic ceramic magnets penetrate 4.25 inches. The surface field strength and the
depth of penetration are all-important in determining the magnet's effectiveness.
|Depth of Penetration
Maximum Depth of Penetration "Bipolar" (Bioflex, Magnelyfe, Nikken,
TruFit) and "Unipolar" (MagnetRelief, BMI, and Tectonic) Lower Back Units
What about Gauss
What is gauss? The Permanent Magnet Design and Application Handbook by Lester
Moskowitz provides the following definition: The cgs unit of magnetic induction.
For clarification let us proceed to the definition of magnetic induction.
Induction, magnetic (general): The flux per unit area measured at right
angles to the direction of the flux.
If after reading the above definitions you feel that you don't know much more than you
did before reading them, you are not alone.
For our purposes it is probably best to approach this question from a different
direction and establish what gauss in not.
Gauss is not a number which indicates the strength of a magnet.
Unfortunately there isn't a number which describes the overall strength of a magnet in
an open circuit. Magnets used for biomagnetic purposes are described as open-circuit
magnets because they don not have supplemental ferromagnetic parts to provide a complete
path for the magnetic energy. Any type of "bare" magnet alls into this
category. This would include magnets used in mattresses, support items, jewelry, and
When people see magnetic products described in terms of gauss they incorrectly assume
that these magnets have been measured in some way and that this "gauss rating"
describes the strength of the magnet the same way that a gasoline engine could be
described in terms of horsepower or cubic inches.
A gauss meter is and instrument which can be used to measure lines of magnetic
specific point on a magnet, but that reading provides no information about the total
energy of the magnet being tested or about how far the energy will project from its
In describing their products some people talk about the manufacturer's rating.
This number refers to a specific property of a magnet which will be the same for
any size magnet made from the same material. Once again, it is not a measure of the
total energy of the magnet.
The following photographs should illustrate the problems both with using the
manufacturer's rating and with taking measurements with a gauss meter.
|Fig. 1 shows a neodymium-iron-boron magnet next to a Penny. The
manufacturer's rating for this magnet is 12,500 gauss. The flux density on the
surface of this magnet, measured using a gauss meter, is 985 gauss. A simple
magnetometer, another device used to measure field strengths, reads 2 gauss at a distance
of 1/8" from the surface of the magnet.
|Fig. 2 shows a ferrite ceramic magnet next to a Penny. The
manufacturer's rating for this magnet is 3850 gauss. The flux density on the surface
of the magnet, measured using a gauss meter, is 565 gauss. The magnetometer reads 2
gauss at a distance of approximately 3/4" from the surface of the magnet.