Pressure measurement because atmospheric pressure is always changing and the reference in this case is fixed at 1 bar. To produce an absolute pressure sensor, the manufacturer seals a high vacuum behind the sensing diaphragm. If the process-pressure connection of an absolute-pressure transmitter is open to the air, it will read the actual barometric pressure. The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N·m or kg·m·s). This special name for the unit was added in 1971; before that, pressure in SI was expressed in units such as N·m. When indicated, the zero reference is
Stress–strain curve these two relationships, a relationship of σ=kεἕ can be found. However, as real stresses and strains do not occur uniaxially, considerations for multiaxial stresses must be added to this relationship to model real stresses. This stress is called the tensile stress because every part of the object is subjected to tension. The SI unit of stress is the newton per square meter, which is called the pascal. 1 pascal = 1 Pa = 1 N/m Now consider a force that is applied tangentially to an object. The ratio of the shearing force to the area A is called the shear