In May 2004, the new experimentation and water meter test rig (EWZP) of PTB's department "Liquid flow" could be put into operation. It extends the measuring range of the Hydrodynamic test field towards small flows and is especially designed for the control and metrological testing of domestic water meters.

	The most important metrological characteristics of the test rig are:
	Volumetric flow:	0.01 … 40 m³/h
	Reference method:	gravimetric with 150 kg balance and flow diverter
	Working pressure:	5.3 bar for direct pump operation 3.2 bar for operation with constant head-tank
	Temperature stability:	± 0.05°C during an individual measurement ± 0.1°C during a measurement series
	Expanded measurement uncertainty:	0.05 %

The test rig was put into operation within the scope of a key comparison with five test rigs from verification authorities of Baden-Wuerttemberg, Brandenburg, North Rhine-Westphalia, Saxony and Thuringia. The comparison group was composed of two multiple-jet meters and one oscillating piston meter in a flow range between 0.025 … 5 m³/h. These first results obtained on the new PTB test rig were extremely satisfying. The measurement deviations determined by means of the comparison meters were in very good agreement with those of the other test rigs. It is important to point out the excellent reproducibility of the measured values, which can be seen from the standard deviations having been reached for the performed measurement series. These were clearly smaller for the PTB measurements and generally amounted to only half to a fifth of the values reported by the other test participants. This proved the good measuring stability of the test rig ab initio.