Re: Var. skin imped. match
- From: Bob <bob9@xxxxxxxxxxxxxx>
- Date: Sat, 29 Dec 2007 09:59:37 -0800 (PST)
On Dec 29, 7:14 am, Paul Lewis <paulle...@xxxxxxxxxxxx> wrote:
I refer to figure 4 in the interesting paper below. It is a chart
showing that skin impedance varies from 100 Ohms to 100K Ohms across
the 1MHz to 100Hz range.
I need to build a variable impedance matching circuit for
micro-current skin electrodes that covers this full range.
I am a graduate student in biophysics, but not an electronics
engineer.
https://upcommons.upc.edu/e-prints/bitstream/2117/1401/4/ROSELL-COLOM...
Can anyone suggest an appropriate circuit?
You say microcurrent which suggests to me that you are trying to
measure currents generated by biological processes in the body. Is
this correct?
The study you link to is of the skin impedance when applying a current
to the body from an external energy source.
I doubt that the source impedance of AC signals generated by the
body is anywhere near the same as the load impedance seen when
applying external current.
Externally applied currents will flow through whatever conductive
paths
are available between the electrodes, mostly through the watery
bits I'd guess.
A body generated voltage observed at the skin will have a source
impedance due to the impedance of whatever chemical process
is generating it deep inside the body in a cell or muscle, the
conductive path from whatever is producing the signal and the
shuting effect of current flowing through other conductive bits
of the body instead of out of one electrode and back in the
other.
I think it is unlikely that body generated currents will have a
source impedance as low as 100ohms at external electrodes.
Bob
.
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