What is the instrument used to measure Blood pressure called?

The instrument used to measure blood pressure is called a sphygmomanometer or blood pressure monitor.

It consists of an inflatable cuff, a gauge to display the readings, and a bulb to manually pump air into the cuff. The cuff is placed around the upper arm, and the air pressure in the cuff is gradually increased until it blocks the flow of blood. The gauge measures the pressure at which blood can just barely flow past the cuff and is heard as the first thumping sound, known as the systolic pressure. The pressure is then gradually released and the gauge measures the pressure at which the sound can no longer be heard, known as the diastolic pressure. These two numbers are recorded as the blood pressure reading, for example, 120/80 mmHg.