To use the mercury sphygmomanometer, after the sphygmomanometer cuff and stethoscope body parts are placed in the correct position, inflate the cuff and auscultate while inflating. After the sound of the brachial artery pulsation disappears, continue to inflate so that the mercury column rises another 20-30 mmHg before slowly deflating. Both eyes descend with the mercury column, and look flatly at the surface of the column. The first thing you hear is a loud tapping sound, which represents the value of systolic blood pressure. Continue deflating so that the mercury column descends slowly and evenly, and eventually the diastolic pressure is the value when you hear the sound disappear. Blood pressure should be measured at least twice to be accurate, and if necessary, both upper extremities should be measured. The difference between systolic and diastolic blood pressure is the pulse pressure difference.