Wave shapes and frequencies of PEMF therapy waves

Wave shape  

PEMF therapy devices produce time-varying* electromagnetic waves with a specific shape

 E.g. triangle, rectangular (includes square waves), or saw-tooth. Each wave shape is determined by a specific waveform generator in the device (consisting of circuitry components such as inductors, capacitors, switches, diodes, transistors etc).  *Time-varying means that the electric field has a changing voltage amplitude, achieved by changing the current.

Each wave  shape has 3 variable parameters:

(1) Pulse Rate

How often the EMF pulses are turned on per second. In this diagram, the pulse rate is 1 / T.  E.g. if T=1/10 second,  then the pulse rate = 1 / (1/10) = 10Hz.  The fundamental frequency of the wave is its pulse rate. 

(2) Duty cycle

The amount of time the pulse is active  (t) compared to the time between each pulse (T).   t / T in diagram. E.g.  if T = 1/10 sec. and t = 1/40 sec., then duty cycle = (1/40) / (1/10) =   10/40 = 0.25 or 25%.   A square wave has a duty cycle of 50%. (since t is half of T)

(3)  Strength /Amplitude of Magnetic field (B) and Electric Field (E)

Magnetic field strength is measured in Tesla for large amplitude fields, and Gauss is used for smaller field amplitudes (such as the earth's geomagnetic field of 0.5 Gauss),  and Electric Field (E) is measured in volts /meter.

  Amplitudes are determined by coil shapes /sizes and current flowing through them. Maxwell's equations describe  how a current in a closed loop produces an electromagnetic field (originally Ampere's law).   The electromagnetic field is a physical field, an interdependent relationship between the electric and magnetic fields, which are 90 degrees out of phase (i.e. when E is max, B=0,  when B=max, E=0)

Frequencies

Each of the pulsed wave shapes generates a unique set of FREQUENCIES (called harmonics) as described by the wave's fundamental frequency  and the Fourier transforms of the wave shape (set by device circuitry).    The wave's fundamental frequency is the same as the pulse rate.

Frequency (measured in Hertz) simply refers to the number of oscillations that pass by a fixed point in one second: e.g. the musical note 'A' vibrates at 440 Hz - 440 wave cycles per second.