Measuring skin conductance

Thread Starter

Johnny1010

Joined Jul 13, 2014
96
Hi everyone!

I am trying to measure the skin conductance, for that I found this circuit online.
upload_2015-11-5_3-5-39.png
So from it what I have understood so far:

- There is a low pass active filter at first stage with cut off of 1.6 Hz and variable gain.
- The second stage is also a filter with unity gain and is biased at half the voltage supply and the first stage is biased at the output of second.

What I don't understand:

- Why is the gain variable at first stage as the Rskin chages the gain would change?
- Isn't the first stage enough?
- Can't understand the biasing of the op-amps as well.
 

Alec_t

Joined Sep 17, 2013
10,438
I think the circuit is intended to be an oscillator comprising two integrator stages in a loop, with an oscillation frequency dependent on Rskin. Spice simulation says it doesn't oscillate.
 
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