Auscultation by Sphygmomanometer and stethoscope is the “Gold standard”. The BP reference charts are based on auscultatory BP measurement with mercury sphygmomanometer.
Oscillometry or automated BP measurement.
It measures the oscillations of blood ﬂow instead of Korotkoff sounds using a cuff transducer to detect and send changes in amplitude of arterial wall oscillations to a microprocessor. Mean BP is measured directly and systolic and diastolic BP are derived parameters. Generally, it overestimates the blood pressure. When high BP is recorded, ignore the first reading and take average of next two readings. Any abnormal reading should be further confirmed with auscultation.
Ambulatory blood pressure measurement -uses oscillometric device for taking multiple readings over 24 hr period.
Other methods are Invasive/Arterial BP measurement used in intensive care units & Doppler and finger BP measurements.