Distance From Coils
Some PEMF devices are only able to generate low intensity fields (in the micro Tesla range), however successful PEMF application requires magnetic field strengths into the milli Tesla range.
Low magnetic field strengths are unable to penetrate more than an inch into the body and require very sensitive electronic magnetic field detectors to show that some magnetic field is actually being generated at all.
According to the so called "Inverse Square Law", the pulsing magnetic intensity decreases quickly with distance. This means that If you move away from the therapy pad, the actual magnetic field intensity drops by the square of the distance.
This means that if you have a specific field strength directly at the surface of the pad and you move away from the pad, the magnetic field strength drops fast. If the separation distance increases by a factor of 2, the field strength decreases by a factor of 4. If the separation distance increases by a factor of 3, the field strength decreases by a factor of 9. If the separation distance increases by a factor of 4 the field strength decreases by a factor of 16!