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Pressure gauges are instruments designed to measure the pressure of media in a system, Depending on the area of application of the pressure gauge, Bourdon tubes or diaphragm elements are used as pressure elements.


A pressure gauge is an instrument for measuring fluid intensity in a pressure-powered machine. This fluid intensity is specified by the force that the fluid would exert on a specific unit area.

Typical pressure gauge intensity measurement units are pounds per square inch (psi), or newtons per square meter called the pascal.
Diaphragm pressure gauges are used when a Bourdon tube pressure gauge reaches its limits.

There are many types of mechanical pressure gauges. Three of the most common types are:

1) Diaphragm

2) Bellows

3) Bourdon Tube

In a Bourdon tube pressure gauge , the pressure is measured directly inside the pressure gauge via the Bourdon tube, a C-type curved tube with a non-circular cross-section. As a result of the “tube travel”, thus the movement of the Bourdon tube, the pressure is transmitted via the movement to the pointer to indicate the pressure. Bourdon tube pressure gauges are very versatile and can be used in most applications.
Bourdon tubes have the following advantages over diaphragm elements:
- They cover small pressure ranges from 0 to 0.6 bar up to high pressure ranges from 0 to 10,000 bar.
- They enable accuracies up to class 0.1 of the calibration regulations.
- They are easier to manufacture.
- They can easily be connected or sealed with the pressurised components. Depending on the material and pressure load, they are either soldered, welded or screwed to them.

For diaphragm elements, the elastic deflection of diaphragms loaded on one side, which are clamped at the edge, is determined as a reference value. This deflection is converted via a movement into a rotary motion. Diaphragm elements have a high mechanical stability due to their shape and clamping and are therefore less sensitive to vibration.

Especially when measuring low pressures, diaphragm pressure gauges are used. Due to the large diaphragm area, pressures from 0 ... 16 mbar can be measured (with capsule pressure gauges as a special type of diaphragm pressure gauge, 0 ... 2.5 mbar).

In contrast to Bourdon tubes, diaphragm elements can be easily protected against overload. The overload safety is achieved, for example, through a specially shaped diaphragm bed, against which the diaphragm element can seat.

In addition, diaphragm pressure gauges are used with highly viscous, contaminated or crystallising media, since the diaphragm element can be provided with various coatings, such as PTFE, gold and Hastelloy. A diaphragm pressure gauge with open connecting flange also prevents clogging of the pressure port, since the diameter is larger.

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