Left plot: from bottom to top: weighted average Stokes I LSD profile (black solid line), weighted average LSD profile of the diagnostic N parameter (blue solid line), weighted average Stokes V LSD profile (red solid line), and six Stokes V LSD profiles obtained from the six single observations of β CMa obtained on 21 April 2014. The left panel shows the profiles obtained using a line mask containing He lines, while the right panel shows the profiles obtained with a line mask that does not contain He lines. The FAP-based field detection for Stokes V (see Sect. 3) is given in the top right corner of each Stokes V profile. The two bars at −40 km s^-1 show the average uncertainty of the last single Stokes V profile and of the average Stokes V profile. The vertical dotted lines indicate the velocity range adopted for determining the detection probability and magnetic field value. All profiles have been rigidly shifted upwards/downwards by arbitrary values, and the Stokes V and N profiles have been expanded 250 times. Right plot: same as the plot on the right side of Fig. 3, but for the sequence of observations obtained on 21 April 2014, in sequential order from top to bottom.