Example of a density calibration interval. The probe-to-spacecraft potential V_ps is plotted against low cadence density n_TNR determined by TNR plasma line measurements (black dots). The median for each n_TNR value is indicated by magenta circles. Points at a distance ±1 V from the median are marked as outliers (red dots). If V_sc does not change sign, a linear relation is expected. If V_sc changes sign, two linear fits are required (blue and pink).