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    Resistance data of BME680, normal or abnormal

    EM-1
    New Poster

    Resistance data of BME680, normal or abnormal

    Hello.
    We are doing a test gas detection test using a BME680 pre-mounted board.
    We are using I2C communication between our Raspberry Pi Pico and BME680 board.
    We are testing with 6 BME680 boards.
    When logging resistance data in a clean air environment, we measured inexplicable behavior for 1 of the 6 BME680s.
    It went from the 100k ohm range to the 200k ohm range and then suddenly moved above 400k ohms without showing the 300k ohm range.
    When the BME680 was exposed to the test gas atmosphere, it started to fall from about 430k ohms and suddenly dropped to the 200k ohm range without showing a range in the 300k ohm range.
    In other words, this one BME680 never outputs in the 300 kOhm range.
    Is this an anomaly with this unit?
    Or is it normal for a BME680 to behave this way

    4 REPLIES 4
    BSTRobin
    Community Moderator

    Re: Resistance data of BME680, normal or abnormal

    Hi EM-1,

    The resistance value of your sensor is within the range of the BME680 resistance value output.

    EM-1
    New Poster

    Re: Resistance data of BME680, normal or abnormal

    Thank you for your reply.
    I apologize for the way my post was written.
    Yes, this resistance range is the specification range of the BME680.
    I am attaching a graph of this behavior.

    bme680_resistance_databme680_resistance_dataIt shows the resistance data of one sensor I posted and representative data of 5 other sensors.
    These two data were obtained under the same environment and reacting to the same test gas.
    The data acquisition time is 20 seconds.
    When reacting to the clean ambient test gas, the representative sensor shows a smooth decrease in resistance. (No. 2 on the left)
    However, one sensor shows a jump from 423k ohms to 304k ohms, as shown in the graph. (No. 1 on the right)
    This jump occurred in one sampling of I2C communication.
    One sampling is about 60 msec.
    Is this behavior a specification of BME680?

    EM-1
    New Poster

    Re: Resistance data of BME680, normal or abnormal

    Hello.

    I saw an answer in this thread that this behavior is "normal".
    I would like to ask again.

    The graph below shows the resistance characteristics of two BME680 reacting to the same gas.
    The left one smoothly decreases in resistance, while the right one skips the 300k Ohm range.

    The resistance output of this sensor does not indicate a range of 300 kΩ to 400 kΩ.

    Can this one be considered "good"?BME680Resistance.jpg

    BSTRobin
    Community Moderator

    Re: Resistance data of BME680, normal or abnormal

    Hi EM-1,

    After factory hardware of the BME680 itself is not the same with others, so the resistance is different. If you run BSEC, the sensor will not stabilize until the calibration accuracy is 3. During this period, the sensor resistance value is not same, even if the two sensors are placed in the same environment.

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