For use in an electronic pipette, a brake mechanism which is used for abruptly stopping the movement of the actuator that moves the plunger, which mechanism comprises a rotatable, essentially circular rotor that is at its periphery provided with brake notches arranged at regular intervals, and a brake actuator comprising a motion inducing means, a brake member (1) to which a brake cam (11a), compatible with the brake notches is connected, a mediation mechanism for transmission of the movement of the motion inducing means to the brake member, the brake member comprising, connected to the motion inducing means, a turnable member (2) that is arranged to act with the brake member such that the movement of the turnable member can be accelerated before it essentially effects the movement of the brake member.