Pressure gauges are defined as “an instrument for measuring the pressure of gases or liquids, consisting of a semicircular or coiled, flexible metal tube attached to a gauge that records the degree to which the tube is straightened by the pressure of the gas or liquid inside” 1
Invented and patented by Eugene Bourdon in 1847, the bourdon tube pressure gauge is the second most mass produced instrument in the world, second only to the wristwatch.
The diagram below shows the parts and components that make up a pressure gauge:
Pressure gauges are often categorised in different ways, however, most commonly they are split into two categories:
High Quality Gauges.
These are often used in Dairies, Breweries, as well as the Pharmaceutical and Chemical Industry, and similar.
Low Cost Gauges.
These are commonly used for every day use on Pumps, Compressors, Pneumatic Systems and similar.
Gauge cases are available in various materials:
Stainless Steel 304
Stainless Steel 316L
Carbon Steel (Painted Black)
Plastic (ABS) and Thermoplastics
Cases are available as
ITIUK supply gauges in the following sizes:
40mm (1½ inch)
50mm (2 inch)
63mm (2½ inch)
100mm (4 inch)
150mm / 160mm (6 inch)
250mm (10 inch)
It is important to select a dial size that is easily read at a normal reading distance, once the gauge is installed.
Gauges can be mounted in different ways, either directly or with the use of a mounting flange or clamp fixing.
Most pressure gauges can be supplied with the following connections:
Standard pressure gauges can be supplied with NPT, BSP or BSPT threaded connections.
Threads available in Stainless Steel, Brass & Monel (Wetted Parts)
It is critical that the materials of the gauge’s pressure system are compatible with the media that it’s measuring.
Typical pressure ranges of gauges include:
The gauges lens, or window, can be supplied in the following materials:
Pressure gauge accuracy is the difference (error) between the true value and the indicated reading expressed on the pressure gauge, as a percentage of full scale span.
Usual Accuracy Classes
40mm 1.6 or 2.5%
50mm 1.6 or 2.5%
The accuracy class of a gauge is shown on Dial as Acc, Class, Cl or Kl (e.g. Cl 1.0 for 1% of full scale value).