A method for determining the quality of a break-off of an ink jet of a CIJ printing machine is disclosed. In one aspect, this method includes: generating a first line of N1 drops, all charged by the charge means, at the same voltage V1. Also included is: generating at least one drop G1, charged by the charge means, at a second voltage (VG1), followed by at least one drop G2, charged by the charge means, at a third voltage (VG2) lower than V1; generating a second line of N2 drops, all charged by the charge means, at a same voltage V2; and measuring, using an electrostatic sensor, the charge variation of a non-deflected jet of drops including at least the first line of drops and the second line of drops, separated by the drops G1 and G2, during the passage of the jet in front of the sensor.