Abstract: Measuring device for measuring the flow rate of a gas flow or liquid flow by means of a rotary piston device consisting of two rotary pistons which are placed in a pipe section and are mounted in such a way that they rotate about a rotary shaft, which rotary pistons are placed relative to each other and relative to the pipe section in such a way that by interaction with each other they shut off the pipe section. During the rotation the two rotary pistons always remain in contact with the wall of the pipe section at one side and with each other at the other side, a quantity of gas or liquid being allowed through every turn. The measuring device is characterized in that it consists of a number of parallel branches, with a rotary piston device accommodated in each branch, the rotary piston devices being synchronized with each other by means of synchronization means in such a way that the flow rate is approximately constant.

Abstract: Flow straightener for eliminating vortices in a gas stream through a flow tube. The flow straightener consists of a plate with a circular symmetric hole pattern, wherein the diameter of the holes is smaller than 0.1 times the diameter of the flow tube. The passage area of the holes is between 0.4 and 0.8 times the passage area of the flow tube. The diameter of the largest hole is bigger than 1.3 times the diameter of the smallest hole. The thickness of the plate is between 0.8 and 1 times the square root of the average passage area of the holes. The plate is disposed upstream in front of a turbine-wheel gas meter, which is mounted, so as to run on bearings, on a cylindrical body. In the annular gap between the cylindrical body and the flow tube, a second flow straightener is arranged consisting of a number of vanes, the ratio of the height of the vanes and the spacing between the vanes being between 0.8 and 1.