A sphygmomanometer is a medical device used to measure blood pressure[1][2]. It consists of several key components:

1. An inflatable cuff that wraps around the upper arm
2. A measuring unit (either a mercury manometer or an aneroid gauge)
3. A mechanism for inflation (manual bulb or electric pump)
4. A valve to control air release

The primary purpose of a sphygmomanometer is to determine a person's systolic and diastolic blood pressure[2][3]. Here's how it works:

1. The cuff is inflated to compress the brachial artery in the upper arm.
2. As the cuff is slowly deflated, the examiner listens with a stethoscope for specific sounds (Korotkoff sounds).
3. The systolic pressure is recorded when the first sound is heard.
4. The diastolic pressure is recorded when the sounds disappear.

Sphygmomanometers are crucial in diagnosing and monitoring hypertension (high blood pressure) and are widely used in various healthcare settings[2][4]. They allow healthcare providers to:

1. Assess cardiovascular health
2. Monitor the effectiveness of blood pressure medications
3. Screen for potential health issues related to blood pressure

There are different types of sphygmomanometers, including manual (requiring a stethoscope) and digital (automated) versions[4][5]. While digital monitors are more convenient for home use, manual sphygmomanometers are still considered the gold standard for accuracy in clinical settings.

Citations:
[1] https://byjus.com/physics/sphygmomanometer/
[2] https://en.wikipedia.org/wiki/Sphygmomanometer
[3] https://www.britannica.com/technology/sphygmomanometer
[4] https://www.ncbi.nlm.nih.gov/books/NBK279251/
[5] https://medlineplus.gov/ency/imagepages/19255.htm