GRX-Q - Volumetric measurement methods

With indirect meters, the volume is determined indirectly without a measuring chamber. There are various methods here. For example, the speed of the flow can be measured or the flow values can be integrated over a certain period of time. In this method, the density is usually an important variable to be taken into account, as this has an influence on the error curve of the flow meter.

In the direct methods, small volumes of the medium to be measured are delimited during the measuring process. The volumes are determined by the defined size of the measuring chamber or by the measuring chamber walls. The partial volumes passing through can be recorded and output with the aid of a counter. The direct volume meters are further divided into discharge and displacement meters.

Outlet meters consist of a measuring vessel with fixed measuring chamber walls. The medium to be measured is filled into the measuring vessel by a slight overpressure. The meter then empties automatically by means of tilting or control devices. The fluid flows out of the measuring chamber without pressure (see Fig. 2 4). This method is not suitable for measuring gases. This method can also be used to measure contaminated liquids, as the fluid always flows out through large drain openings or via tilting/rotating devices. The method can achieve accuracies of up to 0.1 %.

Displacement meters are characterized by movable measuring chamber walls that displace the medium to be measured. In contrast to outlet meters, this principle allows liquids and gases to be measured.

Due to the fact that outlet meters always delimit a certain volume, no continuous measurement can be carried out. In addition, the measuring containers are relatively large, which makes implementation in a cooling circuit unattractive. These outlet meters are therefore not suitable for the task at hand. For this reason, only individual displacement meters are discussed below.