The Bourdon Tube is a nonliquid pressure measurement device. It is widely used in applications where inexpensive static pressure measurements are needed.
A typical Bourdon tube contains a curved tube that is open to external pressure input on one end and is coupled mechanically to an indicating needle on the other end, as shown schematically below.

Internal linkages have been simplified.
Beningson explains Bourdon Tube
Bourdon Tubes, also known as differential pressure measurement instruments, come in the category of elastic type pressure transducers. These devices were invented in early 1849 by Eugene Bourdon. The basic idea behind the development of bourdon tube was that when the cross sectional tubes get deformed because of external pressure, they will tend to regain their circular form under the application of pressure. The gauges used nowadays have a slight elliptical cross section and their tubes are bent at an arc length angle of 27 degrees forming a C-shape of the tube. Some of the pros and cons of these types of pressure gauges are:
Pros:
- Simple
- Portable
- Convenient
- Leveling is not required
Cons:
- Only able to measure static or quasi-static measurements.
- Sometimes accuracy is of concern in many applications.