We said that there
were 5 involved impedances. But 2 are negligible
(wire of connection to the generator). In a form,
more complex, the human impedance can be expressed in
the formula ;
This formulation
takes account of the presence of the electrodes.
These electrodes applied directly to the skin form a
capacito-resistive couple, with this one. As we use 2
electrodes (identical surfaces or not), they should
be found in the formula. The third impedance, is
limited to a resistance (by simplification). It is
the resistance of tissues, once the barrier of the
crossed skin.
We
attach to show, in a table, the variations of all
impedances, according to the type of current applied :
| |
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| constant |
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|
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|
| low frequency |
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|
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| medium frequency |
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|
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| high frequency |
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|
 |
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It
is very significant to note that the impedances
above, are valid only insofar as the currents applied
are purely sinusoidal.
