When using your unit at home your readings may be lower due to a more relaxed environment. If you want to compare the readings from the measurements taken with your home unit to the readings taken with the device used by your healthcare provider please follow this direction; use the Omron Blood Pressure Monitor to take the first measurement followed by the unit used in the healthcare provider's office. It is necessary to use the digital unit first because of the different methods used in the devices. The Omron Home Blood Pressure Monitor measures the vibration or movement of blood through your arteries and converts the movement to a digital reading (Oscillometric Method). A doctor listens for sound using a stethoscope and gauge (Auscultation). The artery is constricted during the measurement. Constricting the artery and not allowing the artery to return to its condition prior to the measurement may cause incorrect measurement values when using the digital device.