Hello!
I'd appreciate some help with an issue I'm encountering.
I'm running the square wave voltammetry example on the EVAL-ADucm355 and trying to match the results to a standard Lab potentiostat (PalmSens4). Using a 1 kOhm resistor star I'm able to achieve a close enough match (although with slightly different parameters).
I've performed a SWV test with 5 mV steps and 50 mV amplitude and 4 Hz frequency from -0.1 V to 0.7 V.
Here is the code snippet I used:
pRampCfg->RampStartVolt = -79.0f;
pRampCfg->RampPeakVolt = +721.0f;
pRampCfg->VzeroStart = 1300.0f;
pRampCfg->VzeroPeak = 1300.0f;
pRampCfg->Frequency = 4;
pRampCfg->SqrWvAmplitude = 50;
pRampCfg->LPTIARtiaSel = LPTIARTIA_1K;
pRampCfg->SqrWvRampIncrement = 5;
pRampCfg->SampleDelay = 90;
My aim is to plot the measured current Vs. real time voltage extracted from the REG_AFE_LPDACDAT0 register, in the following way: (Not completely sure this is the best approach)
V = ((AD5940_ReadReg(REG_AFE_LPDACDAT0)&0xfff)*DAC12BITVOLT_1LSB - (AppSWVCfg.VzeroPeak - 200.0f))/1e3f;
And is here is a visualization of the results comparison:
And when zooming in -
The problem begins when I try to perform the same test on a Ferro/Ferricyanide solution (In this case I'm attempting to perform a DPV test by decreasing the reverse current from the forward current). I've managed to achieve similar graphs only when using a voltage range of -320 - 420 mV (rather than the alleged -100 - 700 mV or the previously aligned range of -79-721 mV) -
pRampCfg->RampStartVolt = -380.0f;
pRampCfg->RampPeakVolt = +420.0f;
Obviously the chemical reaction observed by the Lab potentiostat is captured by the ADuCM355 with the modified voltage range.
When trying to use the original range (-79-721 mV) the results aren't near as similar-
My question would be - Why is it that with the resistor star the results relatively match the gold standard (allegedly pointing out that the applied voltage is as we intended) but with the FF solution the same results are obtained with a completely different voltage range.
Thanks in advance :)
