CN0396 Ga sensor LTSPICE model

Hi 

I am FAE in Japanese distributor.

Our customer try to simulate the effectiveness of C4(0.022uF) in CN0396 circuit  by LTSPICE.

I made the gas sensor model. please see the flowing picture.

But I can not judge the model is right.

Could you tell me how to model the gas sensor?

Best regards

N.Kokubo

Parents
  • +1
    •  Analog Employees 
    on Dec 26, 2020 3:38 PM

    Hello Kokubo san,

    Have you contacted the sensor manufacturer? I took a look at the circuit note and the manufacturer's datasheet, and while the behavior of the output electrodes is fairly well specified, you'll have to refer to the manufacturer's appnote for more information on CE. From CN0396:

    ". For a carbon monoxide sensor, oxidation takes place; therefore, the current flows into the working electrode, which requires the counter electrode to be at a negative voltage (typically 300 mV to 400 mV) with respect to the working electrode. The op amp driving the CE terminal must have an output voltage range of approximately ±1 V with respect to VREF to provide sufficient headroom for operation with different types of sensors (Alphasense Application Note AAN-105-03, Designing a Potentiostatic Circuit)."

    AN105-03 is here:

    http://www.alphasense.com/WEB1213/wp-content/uploads/2013/07/AAN_105-03.pdf

    and provides some details on the headroom required at the CE.

    In general, if a model for a sensor is required, you should contact the manufacturer. Even if you come up with a model that looks like it works properly, there may be some corner case that is not accounted for.

    If the manufacturer can't provide one, then the best we can do is follow their recommended circuit.

    -Mark

Reply
  • +1
    •  Analog Employees 
    on Dec 26, 2020 3:38 PM

    Hello Kokubo san,

    Have you contacted the sensor manufacturer? I took a look at the circuit note and the manufacturer's datasheet, and while the behavior of the output electrodes is fairly well specified, you'll have to refer to the manufacturer's appnote for more information on CE. From CN0396:

    ". For a carbon monoxide sensor, oxidation takes place; therefore, the current flows into the working electrode, which requires the counter electrode to be at a negative voltage (typically 300 mV to 400 mV) with respect to the working electrode. The op amp driving the CE terminal must have an output voltage range of approximately ±1 V with respect to VREF to provide sufficient headroom for operation with different types of sensors (Alphasense Application Note AAN-105-03, Designing a Potentiostatic Circuit)."

    AN105-03 is here:

    http://www.alphasense.com/WEB1213/wp-content/uploads/2013/07/AAN_105-03.pdf

    and provides some details on the headroom required at the CE.

    In general, if a model for a sensor is required, you should contact the manufacturer. Even if you come up with a model that looks like it works properly, there may be some corner case that is not accounted for.

    If the manufacturer can't provide one, then the best we can do is follow their recommended circuit.

    -Mark

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