The pressure gauge is a relatively inconspicuous component in pneumatics. However, the importance of the pressure gauge becomes clear when there is no possibility of indicating the pressure of compressed air.
Independent of the size and design, we mainly distinguish between two basic principles.
Bourdon tube pressure gauge
The Bourdon tube pressure gauge is available for the pressure range up to 25 bar.
The Bourdon tubes are circular curved tubes with an oval cross section. When air pressure is applied to the inside of the Bourdon tube, its cross section changes and becomes more circular. The resulting tensions bend open the spring. The unclamped end of the spring reacts to the amount of pressure. A mechanical system picks up and indicates this movement.
The circular springs, which are curved at an angle of approx. 250°, are used for pressures of up to 60 bar. Bourdon tubes are only protected against overload to a certain point.
Capsule pressure gauge
The capsule on the pressure gauge consists of two circular, corrugated diaphragms, connected with each other and pressure-tight around the edges. The pressure is exerted on the inside of this capsule. This generates a stroke movement of the diaphragm, which is picked up and indicated by a mechanical system. Pressure gauges with capsules are particularly suitable for relatively low pressures. They are only protected against overload to a certain extent.
The accuracy class indicates the error margins in percent of the maximum scale reading.
For example: a 10 bar pressure gauge with measuring accuracy class 4 may deviate across the entire measuring range by ± 4% (± 0.4 bar).
|Accuracy class|| error margin|
(Percentage of measurement spread)
Types of pressure gauge
Festo sells a whole range of different pressure gauges. We distinguish not only in terms of accuracy class, but also according to the size, the type of mounting and the display unit.
Standard pressure gauges
This type of pressure gauge is probably the one most often used. The
pressure gauge is simply screwed into the available thread (e.g. onto the pressure regulator)
. It is generally sealed using a compression seal.
Integrated pressure gauge
The special feature of the integrated pressure gauge is that it has
no outward-facing interfering contours. A side-effect of this is the design. It
wouldn't damage the machine/system if, apart from the function, it
was made to look more attractive.
Red-green pressure gauge
Using the adjustable red-green areas, a permissible and
impermissible range can easily be indicated.
Plug-in pressure gauge
Instead of a thread, this pressure gauge has a smooth sleeve with a
groove and a seal. This makes it easy to mount it onto
existing fixtures. Dismantling and assembly is very quick with this
type of pressure gauge.
Plug-in pressure gauge
This extremely small pressure gauge is a special type of plug-in
pressure gauge. Of course, its size affects the accuracy of reading.
In spite of this, there are plenty of applications for which this type is
A pressure sensor is more than just a pressure gauge. Inasmuch as the sensor is equipped
with a display, this can of course be used purely as a
pressure gauge. However, its real task is to
emit a signal when a certain pressure has been exceeded or fallen short of and
transmit this to a higher-order controller in order to start a process.