Blood Pressure Monitor Product

Overview

A blood pressure monitor measures arterial pressure non-invasively by wrapping an inflatable cuff around the upper arm, pressurizing it above the systolic pressure, and then reading how the artery beats as the cuff deflates. An automatic monitor does the whole cycle on one button press: it inflates the Upper-Arm Cuff with a built-in pump, bleeds the air off under control, and reports systolic, diastolic, and pulse on the LCD without a stethoscope or any judgement from the operator.

The unit packs the pneumatic and electronic systems into a desktop Housing Assembly. The arm cuff plugs into an air port on the case; everything else, the pump, valve, sensor, and board, sits inside. Power comes from a Battery Pack that accepts either AA cells or a rechargeable Li-ion cell, so the monitor stays usable as a portable home device.

How it works

When a reading starts, the Main Board runs the Diaphragm Air Pump to inflate the cuff. The pump is a small diaphragm pump driven by a DC motor: an eccentric on the rotor flexes the Pump Diaphragm and check valves set the airflow direction, pushing the cuff pressure up to roughly 30 mmHg above the expected systolic value. The board watches that pressure the whole time through the Pressure Sensing Module, where a transducer feeds the analog signal to the ADC on the board, and a manifold ties the pump, valve, sensor, and cuff into one air path.

Once the cuff is inflated, the board switches off the pump and opens the Solenoid Bleed Valve a controlled amount. As the cuff slowly deflates, blood begins to pulse through the squeezed brachial artery, and each pulse adds a tiny oscillation to the cuff pressure. The board separates these oscillations from the falling baseline, and the oscillometric algorithm finds the point of maximum oscillation, which corresponds to mean arterial pressure, then derives systolic and diastolic from fixed ratios of that peak. Pulse rate falls out of the oscillation timing.

The result appears on the Display Assembly, a segment LCD showing the two pressures and the heart-rate. The user drives the cycle with the Membrane Keypad, a membrane button panel for start/stop and memory recall, and an optional speaker can beep or read the result aloud. After each measurement the valve dumps the remaining air, the cuff goes slack, and the reading is logged so trends can be reviewed later.