Differences and areas of application of pneumatic and hydraulic pressure calibration procedures
Pneumatic and hydraulic calibrators not only use different calibrating media, they also have their own specific application. As pneumatic calibrators can generate a vacuum, they can also be used for calibration in the negative pressure range. The area of application of hydraulic systems, in contrast, starts at 0 bar rel. and extends far beyond the area of application of pneumatic systems with more than 1,000 bar. The calibrating medium is responsible for this. Hydraulic oil allows for a far easier build-up of high pressures than is the case with ambient air. Another factor in the choice of the correct pressure calibrator is the area of application of the device under test which is to be calibrated. In this respect, it is often the case that pressure gauges and pressure sensors must not be wetted or come into contact with hydraulic, aggressive or ionising substances, in the foodstuffs or pharmaceuticals sector, for example. For this purpose, pneumatic or hydraulic pressure calibrators, which can be operated with water, can be used. At over 1,000 bar, systems which work with hydraulic oil are recommended, as this allows for the more straightforward generation of the test pressure due to its higher viscosity.