A typical BPM uses a differential pressure sensor to measure
cuff or arm pressure. As the output of this sensor lies within a
few micro volts (30-50µV), the output pressure signal has to be
amplified using a high-gain instrumentation amplifier with a
good common mode rejection ratio (CMRR). Usually the gain and
CMRR need to be around 150 and 100 dB respectively. The
frequency of oscillatory pulses in the pressure signal lies
between 0.3-11Hz with an amplitude of a few hundred microvolts.
These oscillations are extracted using band-pass filters with
gain around 200 and cutoff frequency at 0.3-11Hz. A 10-bit ADC
with a speed of 50 Hz is used to digitize the pressure sensor
and oscillatory signal. Two timers are used to calculate the
heart rate and implement safety timer functionality. A safety
timer regulates the pressure kept on a subject’s arm for a
certain period of time. This safety timer is a part safety
regulation in AAMI standards. A microcontroller core calculates
the systolic and diastolic pressures va