Bourdon gauge is a mechanical device that is used to measure the pressure of fluids and gases. It is commonly used in various industries to measure the pressure of steam, gas, and liquid.

Gauge Pressure
The Bourdon gauge measures gauge pressure, which is the pressure measured relative to atmospheric pressure. Gauge pressure is the difference between the absolute pressure of the fluid or gas and the local atmospheric pressure. The gauge pressure is measured in units of pounds per square inch (psi) or bar.

Working Principle
The Bourdon gauge works on the principle of elastic deformation. It consists of a hollow tube made of metal (usually brass or bronze) that is bent into a C-shape or spiral. The tube is closed at one end and connected to the pressure source at the other end. As the pressure of the fluid or gas increases, the tube tends to straighten out. This causes the free end of the tube to move, which is connected to a pointer that indicates the pressure on a calibrated scale.

Types of Bourdon Gauges
There are mainly two types of Bourdon gauges:

C-type Bourdon Gauge: In this type of gauge, the tube is bent into a C-shape. It is used to measure low-pressure ranges.

Spiral-type Bourdon Gauge: In this type of gauge, the tube is bent into a spiral shape. It is used to measure high-pressure ranges.

Advantages of Bourdon Gauge
Some of the advantages of using Bourdon gauge are:

- Simple and reliable
- Easy to install and use
- Can measure a wide range of pressures
- Can be used for both gases and liquids

Conclusion
Bourdon gauge is an important instrument used in various industries to measure the pressure of fluids and gases. It measures gauge pressure, which is the pressure measured relative to atmospheric pressure. It works on the principle of elastic deformation and consists of a hollow tube made of metal. There are mainly two types of Bourdon gauges, C-type and Spiral-type, which are used to measure low-pressure and high-pressure ranges, respectively.