Two diaphragms joined together on the border become a differential pressure capsule.

The travel

Depending on the hardness and thickness, the shape and the diameter of the material, differential pressure capsules change their height when under pressure and this change is reproducible. The distance by which the height changes is called "travel" and depending on the application this travel may be taken up by a gauge movement, sender or switch. The travel of a diaphragm capsule can extend up to 5 mm or 0.2"; if this is not sufficient for a particular application two or more capsules may be stacked and their individual travels can be combined.

The standard diameters of Beck's differential pressure capsules are between 10 and 137 mm. For further information please see the chart bellow.

Depending as well on the application the characteristic line of the differential capsule shows the travel in dependence on the pressure. The travel can be made linear or non-linear (e.g. for altitude measurements where the travel is linear in relation to the altitude and not in relation to the pressure ). There is practically no hysteresis.

The materials

The selection of suitabel materials is extremely important and depends on the requirements with regards to corrosion resistance, temperature, elasticity, strength and hardness. Some of the materials Beck uses are: Copper Beryllium (CuBe 2), Nickel Beryllium and Duratherm 600 which can be hardened, and Bronze, Nickel, Silver, Stainless Steel (316 L, 316 Ti) and Hastelloy C.