The Bourdon tube is often shaped in the form of a "C", having an arc span of about:

The Bourdon tube is commonly designed in a "C" shape with a significant arc to enhance its sensitivity and responsiveness to pressure changes. An arc span of approximately 270 degrees is utilized because it allows the tube to respond effectively to varying pressures by converting this mechanical deformation into a rotational movement that can be easily read on a gauge. This design choice results in a large range of motion that increases accuracy and provides a clear indication of pressure levels.

In contrast, options with smaller arc spans such as 90 or 180 degrees may limit the range of pressure detection and could result in less precise readings. A 200-degree arc could be functional but is still less optimal than the maximum range afforded by the 270-degree design. Therefore, the 270-degree arc span of the Bourdon tube is essential for its effectiveness in pressure measurement applications in refrigeration and other systems.