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Need a bit help in understanding effect of resistors in circuit

Discussion in 'General Electronics Discussion' started by Sabz, Mar 20, 2014.

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  1. Sabz

    Sabz

    3
    0
    Mar 20, 2014
    Hello all,

    I added few resistors to my circuit and I observed there is a phase translation of 180 degrees. There is not a shift, where my phase was at 0 degrees without these additional resistors its now at 180 degrees. Same wave as before just translation. I did not understand reason behind it. Magnitude of the circuit has also increased following the same trend.

    So my question is when phase translation occurs and shape remains same what does it mean?

    My circuit is a mixture of capacitors and resistors and to it I attached 2 series resistors and 1 parallel resistor.

    Thanks a lot.
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Sounds like you have a high or low pass filter intentionally or unintentionally. You will get a phase shift dependant on the difference between you frequency and RC time constant.
    Can you supply a drawing of your circuit so it can be analysed properly. With and without the extra components.

    Adam
     
  3. Sabz

    Sabz

    3
    0
    Mar 20, 2014
    Hi thanks for your reply.

    So basically these R1, R2 and R3 are the resistors that I have added. Other RC combinations are matching with the electrodes that I am using in the lab.

    Picture 2 is showing difference between simulation and experimental results without using R1,R2,R3 and picture 3 is showing phase.
    Blue curve is showing experimental results and Red curve is showing simulations results.
    Circuit is a RC network.

    Is there anyway you can suggest I can improve this circuit. I basically have to improve my simulation model to match experimental results.

    The major problem is I have modelled electrodes correctly but what is the other thing that I am lacking :(

    thanks a lot,
    Sab
     

    Attached Files:

    Last edited: Mar 20, 2014
  4. duke37

    duke37

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    Jan 9, 2011
    It would be better if you used standard symbols for the components. Also the curves are not labeled.
     
  5. Arouse1973

    Arouse1973 Adam

    5,164
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    Dec 18, 2013
    If you tell us what it is suppose to do then I am sure we can help.
    Adam
     
  6. Sabz

    Sabz

    3
    0
    Mar 20, 2014
    Hi this circuit excluding resistors R1,R2 and R3 is an electrical model of electrodes that I am using. So if you see 2 graphs I have added, blue waveform is showing actual result that I got in lab using these electrodes. It starts around 10 ohm and goes to around 1 at higher frequencies. Red waveform is the results from simulations and you can see its starting from around 6 ohm and stays fairly constant.

    I modelled electrodes using Ztrim and confirmed it on Matlab too and they seem fine. I am just struggling with what arrangement of resistors I should add to this circuit to make its output matching to blue waveform that is lab results.

    I have now managed to get an output of 6.2 ohm using R1=1000, R2,R3=100 ohm with no phase transition but its not increasing beyond 6.2 ohm.
     
  7. Arouse1973

    Arouse1973 Adam

    5,164
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    Dec 18, 2013
    Ok what is the electrode you are using can you send some details? What are you driving this with, frequency and voltage?
    Adam
     
    Last edited: Mar 21, 2014
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