The current setup is a modification of an original gas mixing setup. Originally, the setup consisted of four lines, and the improvement of the two extra lines is that it gives more accuracy (better resolution, up to three digits after the decimal point) and more flexibility (more mixing options). With respect to the six vs. four lines system, no additional other gases are supplied, but there are different ranges of the flow rate. This means that a higher accuracy can be obtained in a typical (lower or higher) flow range.
In addition to a high level of accuracy, the calibration setup is flexible in the sense that up to 27 different gas compositions can be programmed. The Siemens programmable logic controller (PLC) inside the control box is operated via touch screen to generate the gas mixtures. As some of these compositions have already been programmed in the PLC, the client can simply press one button and start with calibrating using the first gas composition.
The Profibus protocol for (data) communication enhances the flexible control of all instruments together in the setup, making it easy to use. Profibus also allows readout of temperature and other parameters such as setpoint values and measuring values of the flows. Furthermore, measuring data are transferred by USB from the Siemens PLC to the client's personal computer, to log, track and analyse these data using Excel.