Instrumentation Reference Book, 4th Edition

Chapter 14. Measurement of Pressure

E.H. Higham and J.M. Paros

14.1. What is Pressure?

When a fluid is in contact with a boundary, it produces a force at right angles to that boundary. The force per unit area is called the pressure. In the past, the distinction between mass and force has been blurred because we live in an environment in which every object is subjected to gravity and is accelerated toward the center of the earth unless restrained. As explained in Chapter 8, the confusion is avoided in the SI system of units (Systeme International d'Unités), where the unit of force is the Newton and the unit of area is a square meter, so that pressure, being force per unit area, is measured in Newtons per square meter and the unit, known as the Pascal, ...