The present invention proposes a device that is reliable, economical and practical for measuring the speed of calculation of the pulse or blood rigidity. The device according to the invention comprises: two sensors (100 - 200) intended to be positioned in the position of use against the skin of a patient lying on a carotid artery to a femoral artery and each comprising a light source and a light / frequency converter； • a control unit (300) adapted to cause a simultaneous operation of the two sensors (100 - 200), and to record the data sent by the two sensors； a computation unit (400) comprising an input interface of the distance (d) separating the first and second sensor in the position of use, and programmed to: ∘ measure the time difference (dt) between the pulse measured at the level of the carotid artery and the pulse measured at the level of the femoral artery) calculate the rigidity of the blood as being equal to 0,8 x d / dt.
