Capsule spring pressure gauge
For special applications for the precise measurement of particularly low pressures, for example in industrial and process engineering, correspondingly sensitive pressure gauges are available. The capsule-type pressure gauge represents such a measuring device and forms a special design of the known diaphragm pressure gauge. The functional and measuring principle is based here on two superimposed and sensitive plate springs. These are all welded accordingly, thereby forming a can shape. This pressure chamber is colloquially referred to as a load cell.
The medium to be measured is now guided here via a welded capillary tube to the capsule. The spring itself is mounted in the pressure gauge so that both sides of the capsule can bend according to the pressure and thus can perform a double mechanical way despite equal pressurization. This movement can be used metrologically to move a pointer accordingly and thus to be able to map a print size.
Measuring range and sensitivity
For measuring low pressures in air and dry gases, for example, capsule pressure gauges are available. In practice, these cover a measuring range of typically 2.5 mbar up to 600 mbar. Special shapes can also represent a measuring range from 0 mbar to 2.5 mbar. By cascading or series connection of several load cells, the sensitivity of the instrument can be significantly increased. As a result, the lower measuring range can be realized up to approximately 0 mbar. Typical fields of application for capsule-type manometers can be found in medical, environmental or even laboratory technology.
A particular advantage of these sensitive can pressure gauges is the fact that not only pressure, but also a vacuum can be measured. At a negative pressure, the load cell contracts accordingly and thus generates a negative movement on the pointer instrument. Due to the particularly high sensitivity and measuring accuracy, the capsule pressure gauge is also particularly susceptible to mechanical vibration. Therefore, there is the manometer in different designs without and with a liquid housing filling, which consists mostly of glycerol.
A can pressure gauge is often compared or even confused with a barometer. However, a barometer measures in comparison to the manometer but only the „normal ambient air“ and its air pressure. A pressure gauge, on the other hand, basically measures „artificially or mechanically“ generated pressures.