Measuring skin conductance

Discussion in 'The Projects Forum' started by Johnny1010, Nov 4, 2015.

  1. Johnny1010

    Thread Starter Member

    Jul 13, 2014
    83
    2
    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.
     
  2. Johnny1010

    Thread Starter Member

    Jul 13, 2014
    83
    2
    Guys please help me out!!
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,801
    1,105
    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.
     
  4. Johnny1010

    Thread Starter Member

    Jul 13, 2014
    83
    2
    This has got me more confused.
     
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