A sphygmomanometer , blood pressure monitor or blood pressure gauge is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, and a mercury or mechanical manometer to measure the pressure. It is always used in conjunction with a means to determine at what pressure blood flow is just starting, and at what pressure it is unimpeded. Manual sphygmomanometers are used in conjunction with a stethoscope.
A sphygmomanometer consists of an inflatable cuff, a measuring unit , and a mechanism for inflation which may be a manually operated bulb and valve or a pump operated electrically.
The usual unit of measurement of blood pressure is millimeters of mercury (mmHg) as measured directly by a manual sphygmomanometer.