The present invention discloses a measuring assembly device comprising at least a first analyzer for automatically determining the measured variables of liquid and a sample preparation system, wherein the analyzer has at least one sample source, a measuring chamber, at least one supplying, batching or metering system used for conveying a liquid sample to the measuring chamber from the sample source, and a control unit for executing a control analysis cycle in which at least one measurement value of the measured variables is determined. The sample preparation system comprises a supplying system connected with a liquid extraction position via a fluid pipeline and used for conveying the liquid to the sample source from the liquid extraction position, and a filter unit arranged in a liquid path between a sample extraction position and the sample source, wherein the control unit is in bidirectional data communication with the sample preparation system.