AirGradient calibration algorithm

ag_calibrate.py

def calibrate(pm: float, rh: float) -> float:
    if pm < 30:
        return max(0.0, (0.524 * pm) - (0.0862 * rh) + 5.75)
    if pm < 50:
        return max(
            0.0,
            (
                (0.786 * (pm / 20 - (3 / 2)) + 0.524 * (1 - (pm / 20 - (3 / 2)))) * pm
                - (0.0862 * rh)
                + 5.75
            ),
        )
    if pm < 210:
        return max(0.0, (0.786 * pm) - (0.0862 * rh) + 5.75)
    if pm < 260:
        return max(
            0.0,
            (
                (0.69 * (pm / 50 - 21 / 5) + 0.786 * (1 - (pm / 50 - (21 / 5)))) * pm
                - (0.0862 * rh * (1 - (pm / 50 - (21 / 5))))
                + (2.966 * (pm / 50 - (21 / 5)))
                + (5.75 * (1 - (pm / 50 - (21 / 5))))
                + (8.84 * (10**-4) * (pm**2) * (pm / 50 - (21 / 5)))
            ),
        )
    else:
        return max(0.0, 2.966 + (0.69 * pm) + (8.84 * (10**-4) * (pm**2)))