The choice of filling method is based, among other considerations, on the tolerances required. The following methods are usually used by Linde for the filling of
of high quality gas mixtures in cylinders:
- Gravimetric method:
In gravimetric preparation state-of-the-art high-sensitivity, high-load balances are employed. This produces a direct correlation between the weighed gases and the basic unit “kg” or “mole”. If necessary, calibration gas mixtures in the ppm range can be prepared gravimetrically by using suitable “pre-mixtures”.
- Volumetric/Gravimetric method:
This preparation method is a combination method. It is usually employed when minute quantities of calibration components are added to a balance gas, e.g. by means of gas-tight syringes.
- Manometric method:
In this method the pressure changes after adding of the individual calibration components/balance gas are measured. Precision manometers are used for this.