ABSTRACT
Pressure is one of the few fundamental quantities that describes gas behavior, determines gas states, characterizes vacuum regions and vacuum systems, and enables us to determine other physical quantities of gases. The pressure measurement has become possible over large pressure ranges by the combination of different physical principles and using vacuum gauges with special designs. The advancement in microelectronics led to miniaturized gauges that have sensing elements and processing signal electronics on single semiconductor chips. The pressure measurement is profoundly the interaction process of a vacuum gauge and measured environment. Fundamentally, the methods of low pressure measurement can be divided into two categories: direct methods and indirect methods. Direct methods of low pressure measurement enable us to determine pressure by direct measurements of fundamental physical quantities, which are independent of the gas nature. Indirect methods of low pressure measurements permit us to determine pressure by measuring physical quantities, which depend on the gas nature.
