We disclose a portable wearable device for measuring electrocardiographic signals, the device comprising a first portion (105) comprising at least two electrodes (1, 2)； a second portion (110) comprising at least three electrodes (3, 4, 5, 15)； the first portion5 (105) and the second portion (110) being vertically spaced from one another； a controller (12) configured to take: a first potential difference measurement using one of the electrodes (1, 2) of the first portion (105) and one of the electrodes (3, 4, 5, 15) of the second portion (110)； a second potential difference measurement using one other of the electrodes (1, 2) of the first portion (105) and one other of the electrodes (3, 4, 5,10 15) of the second portion (110)； and a third potential difference measurement using one other of the electrodes (1, 2) of the first portion (105) and one other of the electrodes (3, 4, 5, 15) of the second portion (110). The controller (12) is configured to simultaneously take the first, second and third potential difference measurements at three independent positions of a user's body.15
