Use AD5940 for cyclic voltammetry detection

Hi,

May I know what are the start and peak excitation voltage values you wish to set?

Your current RampStartVolt and RampPeakVolt settings are exceeding allowed range.

For example, if the expected start and peak excitation voltage values are -2100mV and -500mV, then 

pRampCfg->RampStartVolt = -2100.0f;           

  pRampCfg->RampPeakVolt =  -500.0f;            

  pRampCfg->VzeroStart = 2300.0f;            

  pRampCfg->VzeroPeak = 2300.0f;               

Hello,

The start and peak voltages of the ramp signal I want to set are -0.8V and 0.8V.

The parameters are set according to the introduction on the official website, as shown in the figure below:

Hi,

 If start and peak excitation voltage values are -800mV and 800mV, then 

pRampCfg->RampStartVolt = -800.0f;           

  pRampCfg->RampPeakVolt =  800.0f;            

  pRampCfg->VzeroStart = 1300.0f;            

  pRampCfg->VzeroPeak = 1300.0f;              

Hello,

If I set it as you said, are the start and peak voltages of the ramp signal passing into the electrode -0.8V and 0.8V?

Why is this different from what is described on the official website?

(from AD5940_Ramp [Analog Devices Wiki])

What is the meaning of setting VzeroStart and VzeroPeak?

Hi,

  Excitation voltage across sensor = (Voltage at CE0 pin) - (Voltage at SE0 pin)

Voltage at CE0 w.r.t. GND at start = RampStartVolt + VzeroStart

Voltage at CE0 w.r.t. GND at peak = RampPeakVolt + VzeroPeak

Voltage at SE0 w.r.t. GND at Start = VzeroStart

Voltage at SE0 w.r.t. GND at Peak = VzeroPeak

Hence, 

Voltage across sensor at start = VCE_start -VSE_start = RampStartVolt

Voltage across sensor at Peak = VCE_peak -VSE_peak = RampPeakVolt

Hello,

I get it.

Thank you very much for your answer.

I'm going to the lab for a test and I'll get back to you later.

Hello,

After setting the parameters according to what you said, the experimental data does become more ideal.

But there are still some problems:

1.When detecting potassium ferrocyanide solution and dopamine solution, the experimental data showed abnormalities at about -0.4V.

(The start and peak voltages of the ramp signal I set are -1V and 0.5V.)

2.For testing the same solution, there are some errors between the test results of the experiment and the test results of the standard electrochemical workstation.

I want to know why these two situations occur and how to improve the measurement results,

Hi,

Kindly refer to (+) Cyclo-Voltammetry example project not giving expected results - Q&A - Precision Microcontrollers - EngineerZone (analog.com)