Pressure switches are designed from Vacuum to pressure. The most important component for controlling pressure is the sensing element. Pressure sensors for both metallic and elastomer are suitable for most applications. Pressure sensors are normally bellows, diaphragms and piston. This works on force balance principle. Media pressure on the sensing element contracts the force of the range spring (adjustable by the adjusting nut) which moves the piston shaft only a few thousandths of an inch to directly actuate the electrical snap action switching element.