CN0357 Board with biased gas sensor O2 3 Electrode

Hi Forum, 

I am new in this forum. I am considering to use attached CN0357 board to read Oxygen Sensor 3 Electrode. But the Biasing current required -600mV.  I have read in this fourm that i need to remove ADR3412 and give biasing voltage instead. my question is that should i give -600mV on this Vref pin. i would be pleased if you could guide me to solve the issue at this initial stage. 

Thanks in advance. 

  • +1
    •  Analog Employees 
    on Jun 10, 2021 1:51 PM

    Hi Sakaz,

    I am assuming the question you read in the forum was the one using the 200mV bias. For your case using the oxygen sensor, the bias of -600mV actually means that the working electrode WE is 600mV lower than the reference electrode. You can still do this using this board with a single power rail. This means you will have to change the vref voltage to 600mV plus the virtual ground voltage (currently at 1.2V). You will also want to change the virtual ground voltage to be lower than 1.2V to make the output swing still centered. You can keep the ADC reference and negative signal input at 1.2V.

    You can check out the "biased sensor circuit with single supply" section in this article for more details: A1A-EC_SENSORS_AN2-Design-of-Electronics-for-EC-Sensors-V4.pdf (sgxsensortech.com)

    Regards,

    Nikko