Bourdon tube pressure gauges are the most commonly used mechanical pressure gauges.The pressure element is often referred to as a Bourdon tube: the French engineer Eugene Bourdon first used the principle of a pressure gauge in the mid-19th century.The Bourdon tube consists of a flexible spring and a C-shaped bend with an oval cross section
When pressure is applied to the interior space of the Bourdon tube, the cross section becomes circular.In this process, a circumferential stress is created, increasing the radius of the C-tube.Eventually, one end of the tube moves about two or three millimeters.This deflection is a measure of pressure.This is transferred to the movement, which then converts the linear displacement to rotational motion, which is displayed on the scale by the pointer