Like electricians,
physicists and other scientists, the men like to
order the things that they govern. The electroones
borrowed from physics a classification. The latter
was adapted, for the needs for medicine.
The currents are
arranged according to three categories :
The low frequency
which covers the spectrum from 0 to 1 000 Hz
The medium frequency of 1 000 to 10 000 Hz.
The high frequency for the frequencies higher than 10
000 Hz.
The effort of
classification is a creditable goal. The adaptation,
with our needs, required a simplification. This
simplification does not go in a scientific way.
Let us take an
example;
Here first of all a square current of 200 Hz, 3
periods are represented ;
Here
now a sinusoidal current of 200 Hz, 3 visualized
periods ;
As I
retained my lesson well, as a kinesitherapist, I can
affirm that these two currents are both low
frequency.
The
further training in electricity, electronics and
digital signal processing allow me to dispute this
assertion. Indeed, only the sinusoidal current is low
frequency. There is a means simple (not simplistic)
to check it ; It is possible to apply, to
the square current, a digital filter which will
prevent any propagation of the frequencies higher
than 1 000 Hz (low frequency limits).
If the
physiotherapistss are in truth, the square current
will be completely transmitted. If the physicists
gain, the signal will be deformed. Here the current
such as it arises from the filter for 1 period ;
The
conclusion is not frankly to the honor of the
physiotherapists. We control only partially our
subject.
