If you are seeing negative ozone measurements, it is not necessarily a problem with the sensor or the calibration of the sensor. Our ozone sensors, like any other analytical instrument, have measurement uncertainty. In short, this means that slightly negative values are to be expected and are not a sign of a malfunction. If you are seeing extremely negative ozone values (less than the stated uncertainty in the respective data sheet), please file a support ticket and we will be sure to investigate.

For more information on why this happens and suggestions for how to handle negative measurements in downstream data analysis, please see this article from our blog.