Barometer

Barometers use MEMS piezoresistive or capacitive pressure sensors to measure atmospheric pressure. A thin silicon diaphragm deflects under pressure changes, altering either the resistance of embedded piezoresistors or the capacitance between electrode plates. Since atmospheric pressure decreases at approximately 12 Pa per meter of elevation near sea level, high-resolution barometers (0.01 hPa) can detect altitude changes as small as 10-20 centimeters. Temperature compensation is critical as pressure readings vary with temperature. In wearables, barometers count floors climbed by detecting elevation gains of ~3 meters, improve GPS altitude accuracy through sensor fusion, predict weather changes via pressure trend analysis, and enhance activity recognition by distinguishing flat walking from stair climbing. Combined with accelerometer and GPS data, barometric altitude enables precise three-dimensional activity tracking.