Gauge (sphygmomanometer) is a medical device for measuring arterial blood pressure in humans. Medical manometer consists of a rubber tube connected to a rubber bulb and cuff, which the doctor wraps the arm of the patient.
In the cuff by means of a rubber pear pumped the air as long as you do not stop the flow of blood through the vessels. This opens the spout and the air begins to slowly walk out of the cuff. At this time, the column of mercury measuring device rushes down. When the heart is able to get under the cuff, the blood, the doctor hears through a stethoscope first kick pulse and record it on the scale. This is the upper maximum limit of blood pressure. In a healthy person, it is 100-120 mm Hg.
Then the pressure in the cuff falls so that it is equalized with the pressure of blood in arteries. The doctor fixes the last blow pulse and notices against any division was at this time the upper bound of the mercury column, it characterizes the lower minimum pressure. It is considered normal when 60-80 mm Hg.