Bourdon Tube

The Bourdon tube works on a simple principle that a bent tube will change its shape when exposed to variations of internal and external pressure. The tube straightens and returns to its original form when the pressure is released.

Bourdon tubes are radially formed tubes with an oval cross-section. The pressure of the measuring medium acts on the inside of the tube and produces a motion in the non-clamped end of the tube. This motion is the measure of the pressure and is indicated via the movement.

The C-shaped Bourdon tubes, formed into an angle of approx. 250°, can be used for pressures up to 60 bar. For higher pressures, Bourdon tubes with several superimposed windings of the same angular diameter (helical tubes) or with a spiral coil in the one plane (spiral tubes) are used. .

This type of pressure measurement can be used for positive or negative pressure ranges, although the accuracy is impaired when in a vacuum.

Advantages:

• Inexpensive
• Wide operating range
• Fast response
• Good sensitivity
• Direct pressure measurement

Disadvantages:

• Primarily intended for indication only
• Non linear transducer, linearised by gear mechanism
• Hysteresis on cycling
• Sensitive to temperature variations
• Limited life when subject to shock and vibration

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