This makes mostly sense for continuous measurement configuration. Thus, if the interrupt mode is available and a callback function is passed, the interrupt will occur only when the co2 concentration goes above the threshold. This option is better combined with the interrupt mode. In addition to these hardware modes there are also two modes that are achievable by using the library provided which are: Alarm mode : If the alarm threshold argument is non-zero, the alarm mode is activated, and the sensor internal flag will be enabled if the concentration of CO2 goes above the specified value. At the end of the measurement sequence, the device goes back automatically to idle mode.

SINGLE-SHOT : In this mode, the device triggers a single measurement sequence.The measurement period is programmable from 5sec to 4095 sec. Once a measurement sequence is completed, the device goes back to an inactive state and wakes up automatically for the next measurement sequence.

CONTINUOUS : In this mode, the device periodically triggers a CO2 concentration measurement sequence.The device remains inactive until it becomes active shortly to serve interrupts before going back to an inactive state. IDLE : The device does not perform any CO2 concentration measurement.The highly sensitive MEMS acoustic detector detects the pressure change generated by CO2 molecules within the sensor cavity, and the readings of this microphone could be converted to CO2 concentration readings!Ĭheck out this video to find out more! (It's just two minutes don't worry ) The CO2 molecules inside the measurement chamber absorb the filtered light, causing the molecules to shake and generate a pressure wave with each pulse. Well here comes the fancy explanation: the PAS (short for Photo Acoustic Spectroscopy) principle works as follows: Pulses of light from an infrared source pass through the optical filter tuned specifically to the CO2 absorption wavelength (λ= 4.2 µm). Wanna have a more interactive look at the 3D model of the board? Click here to check it out! Underneath the Gas diffusion port, lie the MEMS microphone and the IR emitting source. A port for gas diffusion (copper colored dome that's used to acoustically isolate the measurement chamber from the outside environment).A MOSFET that drives the MEMS heater for the infrared source.It supports interfaces of I2C, UART and PWM This microcontroller runs the compensation algorithms and delivers direct ppm readouts of the CO2 levels.

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