Data from a barometric pressure sensor are used to calculate QNH altimeter setting. An altimeter measures ambient air pressure, which decreases with increasing altitude following the barometric formula. Brode's group investigated the fusing systems, testing radar altimeters, proximity fuses and barometric altimeter fuses. The relative permittivity of air changes with temperature, humidity, and barometric pressure. Increasing the barometric pressure increases the dew point. Fluctuations in weather also affect sufferers, in particularly hot weather and barometric pressure changes. Altitude was maintained by a barometric device. Air density increases with decreasing altitude, at about 1% per (see barometric formula). The boiling point of water is at sea level and at normal barometric pressure. Barometric pressures recorded during the storm were low. He also established the relationship between barometric pressure and height above sea level. "Pressure Drop" refers to the barometric pressure. Barometric pressure plays a role in storm systems. At that, Otto reached its minimum barometric pressure of . The modules were maintained at Earth-normal barometric pressure.