A sphygmomanometer, a device used for measuring arterial pressure.
Blood pressure (BP), sometimes it is called arterial blood pressure, is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. During each heartbeat, blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure. The blood pressure in the circulation is principally due to the pumping action of the heart. Blood pressure is usually measured at a person's upper arm and is a measure of the pressure in the brachial artery, major artery in the upper arm. A person’s blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimeters of mercury (mmHg), for example 140/90.