Improved Operability of the Hydrodynamic Test Field

After having been in operation for more than ten years, the entire IT hardware and software of the hydrodynamic test field has been replaced by new, state-of-the-art computer hardware and the corresponding system and user software. In this way, the reliability, functionality and operability of the plant could be considerably improved.

The Hydrodynamic Test Field (HTF) is the national standard for the volume and flowrate measurements of liquids and is able to realise the respective units (mass and volume flowing, as well as mass and volume flowrate), in a flowrate range from 300 L/h to 2100 m³/h, with an expanded measurement uncertainty of 0.02%. In international comparisons - especially in a BIPM key comparison - this top position of the HTF could be clearly proved at the international level. The structure of this measuring plant and the scope of its functions are shown in a simplified piping and instrumentation diagram (P&I diagram) in Figure 1.

Figure 1: P&I diagram of the HTF

The complexity of the overall system, which comprises two measurement sections and weighing systems that can be selected alternatively (300 kg, 3 t and 30 t), is due to the approx. 500 data points, i.e. data which are either detected by sensors and control devices or are available in the system as the calculated values of composed measurands. The values of all these data points are stored every 2 seconds in a real-time data base system. In addition to these metrological functions, the computer system used in the HTF also carries out the required real-time control and assumes regulating functions.

To cope with these different tasks, dedicated computer components are used. The survey of how the tasks of the above functions are assigned to the different computers, as well as their structural connection, are shown in Figure 2. By updating these system components within the scope of the "large-device project", a significant improvement of both the functionality and the reliability of the plant could be achieved. This is, on the one hand, due to the increased processing velocity of the new computer components and, on the other hand, due to the fact that in each single computer component, the storage media are, as a matter of principle, laid out redundantly.

Figure 2: IT structure of the HTF

Due to the higher reliability of the decentralised data back-up, the additional technical and organisational efforts which would be required for a centralised data backup at PTB's computer centre can be avoided.

As, together with the renewal, also the system software and the user software were updated, considerable additional improvements of the overall system could be achieved (e.g., in the ergonomics of the operation of the plant). Apart from the usual visualisation functions for operating and monitoring the plant, the new user software offers a multitude of functions which enable universal access to historical test and measurement data and, thus, guarantee improved data evaluation (see Figure 3). This functionality is particularly useful when the causes of a possible malfunction of the plant or of a failure of the sensors have to be detected on the basis of the plant's historical measuring data, which are stored in the real-time data base system.

Figure 3: Representation and evaluation of dynamic process data

Contact person:

Dr. Rainer Engel, Department 1.5, rainer.engel@ptb.de