Electric Lodestone Competitive Review

The Electric Lodestone is a pulsed electromagnet designed for the alternative health marketplace. Anecdotally, it relaxes muscles, reduces chronic pain and even speeds healing. Of course, there are literally thousands of magnets on the market, all claiming to do the same thing. How do you make an intelligent choice? We feel you have to understand the basic science of magnetism and compare the published specifications. The important parameters boil down to strength at a distance, rates of change, physical geometry and duty cycle.

Permanent magnets like the ones on your refrigerator are the most common products. The strength of a permanent magnet is steady over time, although it falls off as you move away. Magnetic strength is measured in gauss with the field of the earth being about gauss. The number most often hyped for a permanent magnet is the Residual Field Strength, abbreviated Br. For inexpensive ceramic magnets, Br typically runs 2,000 to 4,000 gauss. For more expensive rare earth magnets, Br may be as high as 14,000 gauss. These values are pretty impressive but they describe the strength deep inside the magnet. On the surface or at a reasonable working distance inside your body, the strength is much lower. It all depends on the size of the magnet and the relative distances.

Let's take a closer look at a large neodymium magnet with a Br of 12,000 gauss. Assume it is shaped like a button with a diameter of 1 inch and a thickness of inch. The field strength on the surface of the magnet would be a respectable 2,600 gauss. But one inch away, it would fall to just 240 gauss. This would be the strength inside your elbow if you were treating it with this magnet. As another example, consider a less expensive ceramic magnet with a diameter of inch and a thickness of 1/8 inch. This smaller magnet would project only 10 gauss inside your elbow. Very few manufacturers reveal these strength at a distance numbers. As you can see, the size of a magnet and the distance to your target are very important considerations.

The Electric Lodestone is an electromagnet that is significantly larger than most permanent magnets. It has a diameter of 3 inches and projects a magnetic field of several hundred gauss inside your body. At reasonable working distances, the Lodestone strength is comparable to that of a large neodymium magnet. Does this allow a direct comparison between Lodestones and permanent magnets? Not necessarily. Permanent magnets are always "on" while electromagnets are pulsed. If you wore a permanent magnet for 8 hours, you would get a full 8 hours of therapy. But Electric Lodestones are pulsed at a duty cycle of about 3% and they are conveniently used for much shorter 15 minute sessions. This works out to only minute of actual "on" time when the electromaget is energized. If you are just interested in therapy time, a permanent magnet would be the winner. But here is where the science comes in.

When a magnetic field changes, an electric field is created which drives tiny electric currents in living tissue. This is known as the Faraday Effect and is one of the basic laws of electromagnetism. The faster the magnetic strength changes, the greater the Faraday currents. And, the larger the area affected, the greater the current. Faraday currents are the primary means by which pulsed electromagnets affect biology. Permanent magnets have a steady field and produce no Faraday currents although they may offer medical relief by other means.

For a round geometry, the formula for the electric field induced by the Faraday Effect is given below. Note dB/dt is the rate of change of the magnetic strength and R is the inner radius of the electromagnet coil.

Pulsed Electric Field = (dB/dt) times (R/2)

For medical applications, the duty cycle is also important. If the electromagnet produces only a few pulses per minute, it will be less effective than one running at many pulses per minute. And if the pulses are too short, they will not accomplish as much as longer pulses. The duty cycle is defined as the time "on" divided by the time "off". If we multiply the Pulsed Electric Field by the duty cycle, we get a time averaged electric field that is a good figure of merit for electromagnets.

Average Electric Field = (Pulsed Electric Field) times (Duty Cycle)

Electric Lodestones have an inner radius of 3.5 cm and rates of change of several hundred gauss per millisecond. They run at 8 to 12 pulses per second with a duty cycle of about 3%. And they produce electric fields that mildly affect living tissue at about 1% of the motor threshold of nerves and muscles. That means it would take an electromagnet 100 times stronger to actually trigger your nerves or make your muscles twitch. Armed with these formulas and numbers, we can compare the Electric Lodestone to other magnets.

One of the more popular electromagnets is the MPG5 by SOTA Instruments of Canada. It is just slightly more expensive than Electric Lodestones and it has some pretty impressive specifications. For instance, it claims a magnetic field strength of 43,133 gauss. Wow! Of course, like the Residual Field Strength of the permanent magnets, this is the strength inside the coil windings under a plastic cover. In other words, you can't get there. The strength at the surface is 6,000 gauss. Not bad! And at elbow distances of about an inch, the strength is down to 1750 gauss. All of this is interesting, but what about the Faraday Effect? As discussed earlier, this depends on the rate of change of the magnetic field, the inner radius of the coil and the duty cycle. If you work through the numbers, the peak Pulsed Electric Field of the SOTA coil at 2 cm from the surface is comparable to that of the Electric Lodestone. But the Average Electric Field of the SOTA is way below that of the Electric Lodestone. This is because of the low duty cycle of the SOTA, much less than one short pulse every second. Whereas, the Lodestones run at 8 to 12 pulses per second. This makes the Average Electric Field of the model MP100 Electric Lodestone 23 times higher than that of the SOTA. And the model MP200 Lodestone is 31 times more effective.

Comparison of Electric Lodestone and SOTA Electromagnets


Lodestone 100   Lodestone 200   SOTA MPG5  
Price $148 $198 $265
Coil Inductance 0.5 mH 0.5 mH 2.5 mH
Peak Voltage 15 volts 30 volts 330 volts
Peak Current 20 amps 40 amps 150 amps
Peak Rate of Current Rise 30 amps/ms 60 amps/ms 132 amps/ms

Coil Inner Radius 3.5 cm 3.5 cm 1.0 cm
Pulse Width 3.0 ms 3.0 ms 2.5 ms
Pulse Frequency 12 pps 8 pps 0.21 pps
Duty Cycle 3.6 % 2.4 % 0.053 %

Magnetic Field at 0 cm 130 gauss 260 gauss 6,000 gauss
Magnetic Field at 2 cm 100 gauss 200 gauss 1,750 gauss
Peak Gauss Rate at 2 cm 150 gauss/ms 300 gauss/ms 1,540 gauss/ms
Peak Electric Field at 2 cm 265 mv/meter 530 mv/meter 770 mv/meter
Mean Electric Field at 2 cm 9.5 mv/meter 12.7 mv/meter 0.41 mv/meter

Effectiveness versus SOTA 23 times 31 times 1 times

Another similar electromagnet is the MagPulse Series 100, although it is twice as expensive as the SOTA. The MagPulse is shaped like a wooden mallet and the website gives very little data other than peak gauss ratings. It boasts an impressive 10,000 gauss at its coil surface but this drops to about 1,000 gauss at an inch. Since this is a steeper drop than the SOTA, I assume it implies the coil radius of the MagPulse is somewhat less. Also, the risetime is stated to be 4ms which is longer than the SOTA and would result in slower rates of change. The pulse frequency is not given, but from heating arguments, I would assume it would be similar to the SOTA. All of this considered, the MagPulse would have smaller Faraday Effect electric fields and be around 50 times less effective than Electric Lodestones.

Electric Lodestones may be operated in either a steady therapy mode or modulated at 1 to 4 hertz, promoting deeper relaxation by influencing the brainwave state. Smooth sine wave or sharp square wave modulation may be selected by convenient DIP switches. An LED flashes in unison with the magnetic pulses, providing a visual presentation of both steady and modulated operation. Neither the SOTA nor the MagPulse electromagnets are capable of modulation.

Other competitive electromagnetic products are not very competitive. They seem to fall into two categories: very expensive or very weak. Therion Research sells their Model 2000HP therapy station for $2,695. It's an elegant system, complete with a control unit, a mattress and a smaller therapy pad. The mattress and pad contain multiple electromagnets which operate in the 5 to 200 gauss range, although the rates of change are not specified. It seems to be a well designed product, but who has $2,695 to find out. Similarly expensive is the Quantum Resonance System which sells for $2,650. The Quantum Resonance System is also an electromagnetic mattress, but from the advertisements, it seems to operate at very low magnetic strength. It claims to be able to resonate at the natural frequencies of body organs. As far as I can tell, there is no support for such a theory in the scientific literature. They also claim to have sold 50,000 of these units in Europe. At $2,650 each, Europeans must be better off financially than Americans.

The Max Stress Controller produces a very weak magnetic field at half the price of a SOTA or Electric Lodestone. The Max Stress is battery powered which is a good clue that it is not going to be very useful. Strong electromagnets are power hungry beasts. No real technical information is published but I have evaluated the device using a gauss meter. At the case surface, the magnetic field strength is only 1/5 gauss, less than the earth's field. A few centimeters away, I couldn't even measure it. I can't imagine how such a device could be taken seriously. Another similar product is called Bio-Medici and sells for $168. It proudly claims to generate a broad spectrum of positive, harmonious, bio-magnetic stimulating pulses. It also pegs the magnetic strength at a whopping 5 milligauss. This is 100 times less than the field of the earth and I'm surprised they even publish it. The Max Stress is made in Spain and the Bio-Medici is German. I guess there are a lot of very sensitive people in Europe.

If I were recommending magnetic products, I would start by suggesting a permanent magnet wrap with large diameter, thick magnets. Size is more important than strength if the target is well inside your body. Permanent magnets are convenient, provide a 100% duty cycle and seem to help many people. If the permanent magnets don't work, perhaps they can be returned and an electromagnet tried. I would stay away from battery powered units and look for something with a large coil and a magnetic rate of a hundred gauss per millisecond or higher. Perhaps an Electric Lodestone?

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