| 摘要 |
Liquid transfer device for an analysis unit with a capacitive liquid level detector (10) for detecting the dipping of a liquid transfer needle (5) into an analysis liquid (4). More reliable operation, in particular a better ratio between useful signal and noise signals, is achieved by the fact that the liquid transfer needle (5) is part of a coaxial electrode arrangement (11). The coaxial electrode arrangement includes, in addition to the liquid transfer needle (5), at least one coaxial electrode (12, 13) surrounding the needle and insulating from it and a detection circuit (17). This detection circuit detects a change in capacitance between the electrodes (5, 13) of the liquid level detector (10), and includes an isolation amplifier circuit (23) to whose input (23a) and output (23b) two adjacent electrodes (5, 12) of the coaxial electrode arrangement (11) are connected as signal electrode and compensating electrode. As a result of this structure, no voltage difference occurs between the signal electrode and the compensating electrode.
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