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3 electrode EIS measurement using AD5940 EVAL ELCZ

Hello AD Team,

I have purchased AD5940 EVAL ELCZ board 

I want to perform EIS measurement for a 3 electrode system

Working electrode - Gold

Counter electrode - Platinum 

Reference electrode- Ag/AgCl (0.21 V vs Standard Hydrogen Electrode)

Calibration settings :

frequency range: 1KHz to 10Hz

Bias voltage: 300mV vs Ag/AgCl reference electrode

In the AD5940_examples code for impedance measurement , the method used was Sense electrode connected to AINx pins which was a 2 electrode system (WE :AINx and CE: CE0)

How do I modify this code to accommodate a 3 electrode system as given above ? What should be the switch matrix configuration ?

Kindly guide me through the process 

  • Hi,

    The switch settings may be

    .DswitchSel = SWD_CE0,
    .PswitchSel = SWP_RE0;
    .NswitchSel = SWN_AIN1|SWN_SE0;
    .TswitchSel = SWT_AIN1|SWT_AFE3LOAD;

  • Thank you Akila
    The switch settings worked
    Do you know how to set VBias and VZero separately ?
    I was able to change BiasVolt values but i couldn't find a way to change Vbias and Vzero. 

  • Hi,

    Vzero is set by 

    AppIMPCfg.Vzero 

  • Hi,

    AppIMPCfg.Vzero  does not exist in Impedance.c and AD5940_Impedance project 

    Could you please check into this?

  • Hi,

    Can you search for AppIMPCfg.Vzero in Impedance.c

  • Hi,

    I think we both have 2 different version of Impedance.c . The one i have was downloaded from AD5940_example github.. Could you share your version ?

      

  • Hi,

    Thank you for that link.

    For our experiment we have to measure RzMag and RzPhase for a 3 electrode system

    Problem : The phase values must be in the range of 0 to -90 degrees , but the phase values were going shooting up and down going out of bounds.

    What can we do to get phase values within the range?

    I have added the settings we used below

    RcalVal Pwrmod LptiaRtiaSel LpTiaRf LpTiaRl HstiaRtiaSel ExcitBufGain HsDacGain DacVoltPP BiasVolt Vzero LpAmpPwrMod HstiaCtia HstiaDeRload HstiaDeRtia
    5000 AFEPWR_LP LPTIARTIA_6K LPTIARF_1M LPTIARLOAD_100R HSTIARTIA_5K EXCITBUFGAIN_0P25 HSDACGAIN_0P2 20 194mv 310mv LPAMPPWR_NORM 31 HSTIADERLOAD_OPEN HSTIADERTIA_OPEN

    The outputs obtained from AD5940 EVAL ELCZ are

    Freq Mag Phase Phase(Radians) Real Part Imaginary Part -Imaginary Part
    Freq:300.00 18598.55469 21.68462 0.3782761489 17283.68648 6868.800355 -6868.800355
    Freq:236.54 9125.26465 -19.72364 -0.3440679422 8590.435285 -3078.12874 3078.12874
    Freq:186.51 5342.30371 -41.27015 -0.7199348389 4016.604066 -3522.37146 3522.37146
    Freq:147.06 14166.83984 -84.70303 -1.477597301 1318.425081 -14105.35736 14105.35736
    Freq:115.95 672.85523 0.61284 0.01069065333 672.81678 7.193124988 -7.193124988
    Freq:91.42 119.63677 2.36565 0.04126745 119.5349136 4.935703227 -4.935703227
    Freq:72.08 724.7486 102.98277 1.79647721 -162.1770169 706.3704045 -706.3704045
    Freq:56.84 346.73135 145.50624 2.53827552 -285.5187328 196.7274314 -196.7274314
    Freq:44.81 425.25339 132.86993 2.317842112 -288.9487167 312.0081487 -312.0081487
    Freq:35.33 251.71271 -178.63466 -3.116182402 -251.6314513 -6.395394951 6.395394951
    Freq:27.86 172.66576 173.08084 3.019299098 -171.3761986 21.06331519 -21.06331519
    Freq:21.97 626.93933 -140.72044 -2.454789898 -484.7979112 -397.5222117 397.5222117
    Freq:17.32 365.97711 -62.2551 -1.086005633 170.553817 -323.8064863 323.8064863
    Freq:13.66 247.9153 -43.807 -0.7641887778 178.9809439 -171.5453809 171.5453809
    Freq:10.77 862.71643 13.38434 0.2334823756 839.3079909 199.6039452 -199.6039452
    Freq:8.49 804.01599 -41.06674 -0.7163864644 606.3756139 -527.9681118 527.9681118
    Freq:6.69 817.92841 -67.3604 -1.175064756 315.2977619 -754.7146515 754.7146515
    Freq:5.28 879.36475 91.00647 1.58755731 -14.73832771 879.2412327 -879.2412327
    Freq:4.16 356.60803 153.05237 2.669913566 -317.6687852 162.0365081 -162.0365081
    Freq:3.28 1278.87671 -7.29908 -0.1273283956 1268.523801 -162.3976756 162.3976756
    Freq:2.59 1050.96765 54.64161 0.95319253 608.5977899 856.8207114 -856.8207114
    Freq:2.04 408.53467 -176.60107 -3.080707554 -407.7776858 -24.85830897 24.85830897
    Freq:1.61 595.61542 -163.24927 -2.847792821 -570.0935313 -172.4850546 172.4850546
    Freq:1.27 851.45184 -150.89906 -2.632350269 -743.4146135 -415.096312 415.096312
    Freq:1.00 1176.3042 -140.24664 -2.44652472 -903.4136196 -753.349456 753.349456

    The Nyquist plot for the above table 

      

    The Expected Nyquist Plot (Obtained from electrochemical Workstation)