Bourdon Tube

A Bourdon tube is used for measuring pressures outside the range of the mercury filled manometer. A Bourdon tube is simple and versatile. A Bourdon tube is also the basis of many types of pressure gauge. A Bourdon tube is shown below.

In its simplest form the Bourdon tube consists of an oval section tube bent into a circular arc. One end of the Bourdon tube is sealed and free to move. The other end of the Bourdon tube is rigidly fixed and is open for the transmission of pressure.

The Bourdon tube uses a pointer to indicate the pressure applied to the Bourdon tube, as shown in the Bourdon tube figure. With some internal pressure the Bourdon tube section becomes rounder and this causes it to become straighter. It is this motion, amplified mechanically, which is indicated by the gauge needle. 

Figure 6: Bourdon Tube

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