A bellows is a tubular, elastic, and sensitive component formed by connecting foldable, corrugated sheets along the direction of expansion and contraction. Widely used in instrumentation, bellows primarily serve as sensing elements in pressure-measuring instruments, converting pressure into displacement or force.
Bellows feature thin walls and high sensitivity, with a measurement range spanning from tens of pascals to tens of megapascals. One end is fixed, while the other-the sealed end-remains free; auxiliary helical springs or leaf springs are often employed to enhance elasticity. Under internal pressure, the bellows elongate along their longitudinal axis, causing the free end to undergo a displacement that is proportional to the applied pressure.
This moving end can drive a pointer to provide a direct reading of the pressure. Bellows are frequently paired with displacement sensors to create pressure transducers that produce an electrical output; they are also sometimes used as isolation elements. Because the expansion of a bellows requires a significant change in internal volume, its response speed is lower than that of a Bourdon tube. Bellows are well-suited for measuring low pressures.