First critical nozzles test rig for domestic gas meters – PGJE

The first test rig, which was working with critical nozzles as a standard only, was developed in 1983. The energy company “Energiekombinat Potsdam” and the “ASMW” as the measurement certification authority of the GDR were looking for better test possibilities for domestic gas meters. Bell Provers were used up to this time, without good automation benefits.

It was build up the PGJE – Prozessrechnergesteuerte Gaszähler Justier- und Eicheinrichtung (Process Controlled Gas Meter Calibration and Verification Rig)

The material of the first nozzles was brass and machined by a watchmaker. The computer core was a U808, the previous circuit of U880 (Z80) with a whole storage range of 16 Kbytes. It was divided in 2 Kbytes RAM the other EPROM circuits. This rig worked already with an automatic optical detection. An optical system with normal light detected the small lines on the last counter roll in all test points. This self development was working with a self contrast adjusting. The temperature was measured with semiconductor sensors on each Bench in the upstream and downstream pipe and in the nozzles block. The temperature sensors were also self developed and had for these times a high accuracy of 0,1 K. The differential pressure was electronically measured from each separate meter and used for the error correction and pressure drop control. So it was possible the past to use for flow calculations the direct input of pressure and temperature values into the computer, like the current technology. Two benches were connected on one rig. They were used reciprocally and a complete test run of both benches (12 meters) takes less than one hour for verification with adjusting and leakage test.

Altogether 7 pieces of these rigs PGJE were assembled and used. Three rigs were working in the meter repairing company in Hecklingen, two rigs in Gotha and one at a time in Dresden and Rostock.

With taking over the law for measurement devices of the Federal Republic of Germany to the new German countries, the test rigs lost their certifications. In 1991 Mr. Fabian went to the Local Weights and Measures Office Sachsen Anhalt to get a certification for one of these critical nozzles test rigs. The PTB was requested for technical assessment and they fixed the requirements for such kind of rigs.

Many things must be changed like software, sensors, test procedure and the leakage test. At first time the nozzles were manufactured from a company in Gröbzig from high-grade steel. Up to today the most nozzles for test rigs were produced by this company. With the reconstruction of the rig also the flow pulse detection was changed. To the common use of a reflection sensor with an adjustment star, the detection of the inside magnet of the magnetic coupling by Hall-Sensors was added. This new system was very effective and reliable.

After the reconstruction, the uncertainty proof and the inspection on 17^th September 1991, the first test rig for domestic meters, working with critical nozzles as standards only, was certified by PTB. This was the hour of birth of the critical nozzle test technology for gas meters in the united Germany.

Afterwards other manufacturers of test rigs took over this technology. They used the same nozzles producer, after they had no success reaching this stability with own nozzle developments and other producers.