Electronic system to control the acquisition of an electrocardiogram, the system comprising a portable electronic device and a mobile electronic device, the mobile electronic device comprising: - an optical device for acquiring real-time images of a portion of a human body; - a screen; - a processing unit connected to the optical device and to the screen; the portable electronic device comprising: - a first, a second and a third electrode configured to generate a first (S1_r), a second (S2_r) and a third (S3_r) detecting electrical signal respectively representing the current generated on the skin by the activity of the heart of a human being in the respective points wherein the first, second and third electrodes are positioned on said portion of the human body; the processing unit of the mobile electronic device comprising an electrodes placement guiding module (3-3.1) for the first, second and third electrode, wherein the electrodes placement guiding module is configured to: • receive a plurality of real-time images (I 1, I 2... I n) representing the portion of the human body and characterized in that the guiding module is further configured to: • identify a feature of the portion of the human body within at least part of said plurality of images; • calculate, as a function of the identified feature, the positions wherein to apply the first, second and third electrode on the portion of the human body; • generate a driving signal (S_pl) carrying information indicating the calculated positions wherein to apply the first, second and third electrode; wherein the screen is configured to: • receive said driving signal; • display a real-time image (I_ps_el) representing said portion of the human body and further comprising a first positioning mark, a second positioning mark and a third positioning mark representing the positions wherein to apply the first, second and third electrode respectively. - an optical device for acquiring real-time images of a portion of a human body; - a screen; - a processing unit connected to the optical device and to the screen; - a first, a second and a third electrode configured to generate a first (S1_r), a second (S2_r) and a third (S3_r) detecting electrical signal respectively representing the current generated on the skin by the activity of the heart of a human being in the respective points wherein the first, second and third electrodes are positioned on said portion of the human body; • receive a plurality of real-time images (I 1, I 2... I n) representing the portion of the human body and characterized in that the guiding module is further configured to: • identify a feature of the portion of the human body within at least part of said plurality of images; • calculate, as a function of the identified feature, the positions wherein to apply the first, second and third electrode on the portion of the human body; • generate a driving signal (S_pl) carrying information indicating the calculated positions wherein to apply the first, second and third electrode; • identify a feature of the portion of the human body within at least part of said plurality of images; • calculate, as a function of the identified feature, the positions wherein to apply the first, second and third electrode on the portion of the human body; • generate a driving signal (S_pl) carrying information indicating the calculated positions wherein to apply the first, second and third electrode; • receive said driving signal; • display a real-time image (I_ps_el) representing said portion of the human body and further comprising a first positioning mark, a second positioning mark and a third positioning mark representing the positions wherein to apply the first, second and third electrode respectively.