ESTEEM

[Guest guest]

For those of you that are interested in the physics of electrostim here is the

physics beyond symmetrical and asymmetrical waves. As you can see this as

nothing to do with Net-DC

Unfortunately I cant email the figures but i will have them in my book.

Alon

 

An oscillating voltage wave form applied to a device is able to produce

instantaneous power equal to the square of the current times the resistance of

the circuit where the power is expended (P=I2 R). Based on this, it can be

derived that the average power (Pav) expended in a circuit for a sine wave

(alternating current) is the sum of all incremental ordinates squared time the

resistance (the same applies to voltage V since V= I R, and R is a constant). By

means of mathematical calculus, the result can be demonstrated to be: Paw = 1/2

R Im2 (R= resistance of circuit, Im = maximum ordinate of the sine wave). Assume

now that the same resistance is calculated in a Direct Current (DC) circuit

until the power dissipated is equal to that dissipated by the resistance in an

AC circuit. We can explain this as RI2=1/2 RI2m or I=1 divided by square root of

2 times Im; or 0.707 Im. This is called the effective current. Following the

same method for a triangle wave (fig b) it can be demonstrated that Ieff =1

divided by square root of 3 times Im; or Ieff =0.578 Im. Now if we have an

alternating wave as shown in fig c (approximation of real output curves of

acupuncture simulators) in which a=0.578 b, the effective value of the

triangular side of the wave will be equal to that of the square side (equivalent

to DC input). The DC voltage equivalent of the alternating wave shown

(asymmetric biphasic square wave) will be zero. The energy produced (power

during a lapse of time) will be the sum of the one produced by the square wave,

plus the one produced by the triangular wave.