AEM offers high quality stainless steel PSIa sensors in 15 (1BAR), 30 (2BAR), 50 (3.5BAR), 75 (5BAR) and 100 (7BAR). PSIa is referenced to absolute zero. Absolute zero is the pressure measurement when all the pressure exerted by the atmosphere has been removed. The most common use for absolute pressure sensors is reading manifold pressure.