Abstract: The invention relates to an invention for compensating for play in a measuring system in which a measuring arrangement is connected via a mechanical transmission system to a body, the movement of which is to be measured, and in which the measuring result is processed in an electric signal processing unit. The moveable body is provided with a friction coupling and a friction rod extends through the friction coupling. The rod is provided with a stationarily mounted arrangement which counteracts movement of the friction element and detects the occurrence of a counteracting force. This force can be detected electrically. The signal processing unit has a control input which is connected for sensing the arrangement and processes solely signals obtained from the measuring arrangement when a counteracting force is detected.

Abstract: The invention relates to apparatus for manipulating small quantities of liquid, comprising at least one test tube for accommodating the quantity of liquid, a cannula which can be inserted into the vessel, and a control arrangement for controlling the system vessel and cannula in relation to one another in a manner such as to bring the cannula to the bottom of the vessel. In accordance with the invention, the cannula is provided with a suspension structure which is connected to a mechanical or electronic sensor arrangement which records pressure acting axially on the end of the cannula. When pressure is detected, the control arrangement halts further insertion of the cannula into the vessel.