Devices — located along the signal flow — which make up a measuring device and whose measuring characteristics (errors, chain of influences) are specific to the measuring device in question (Figure M 20).
A distinction is made between measuring instruments with direct output (measuring instruments performing registration or counting tasks, measuring instruments with a display based on a scale or digits) and measuring instruments involved in some kind of transmission (measuring instruments with indirect output such as measuring amplifiers, transducers and measuring converters) (VDI 24 2600).
Figure M 20: Classification of measuring instruments