The weight fluctuations you measured would appear to be a temperature problem. Please ensure that the pipette, the distilled water used for testing, the tips etc. are all at the same temperature. It is recommended that the pipettes be placed in the weighing room at least 2 hours before the test is performed. While measuring, ensure that transfer of heat from your hands is kept to a minimum (otherwise weight fluctuations may occur!) Tip: do not constantly grasp the pipette in the palm of your hand while waiting for each measurement result! We recommend our standard operating procedure (SOP) for pipettes as a source of basic information on pipette calibration.