The gauge needle flutters due to vibrations and pressure peaks in hydraulic systems. Gauges are filled with glycerine to dampen this movement. This makes the gauges much easier to read.
Gear flow meters can measure very small volumetric flows down to 1 l/min highly accurately. The oil flow moves two gears which are engaged with one another, a transducer detects the motion and creates an electronic signal from which the flow can be deduced.
Measuring accuracy determines how much the displayed value and the absolute physical value differ from one another. Depending on the measurement principle, the accuracy is given either in terms of the full-scale value (the maximum value measurable by the device) or the actual physical reading.