Hoffmann-la Roche Inc.

Thomas Caratsch

Rolf Moser

Guido Bonacina

An analyzer has a horizontally disposed baseplate on which primary containers and secondary containers are disposed; a pipetting needle of an electrically conductive material connected to a metering device by a tubing, for transferring a predetermined volume of liquid each time from a primary container to a secondary container; a transport device for the controlled transport of the pipetting needle in three directions at right angles to one another, two of the transport directions extending horizontally and the third transport direction extending vertically; an electrically conductive reference body rigidly connected to baseplate and which in each of the horizontal transport directions has two outer surfaces disposed perpendicularly to the transport direction; and a control device for controlling the metering device and the transport is device. For fine adjustment of the pipetting needle transport device, there is provided a circuit for measuring the electrical capacitance between the pipetting needle and the reference body, and a device for determining the coordinates of a reference position of the pipetting needle in at least one of the horizontal transport directions. The device is adapted to move the transport device of the pipetting needle so that the pipetting needle is moved in opposite directions in each case to a position near each of the two outer surfaces of the reference body. The pipetting needle is moved in each case towards a surface of the reference body until the value of electrical capacitance between the pipetting needle and the reference body, as measured by the circuit, reaches a predetermined value corresponding to a specific distance between the pipetting needle and the surface of the reference body.

Apparatus for capacitatively determining the position of a pipetting

An analyzer has a horizontally disposed baseplate on which primary containers and secondary containers are disposed, a pipetting needle, a transport device, and a control device. The pipetting needle is formed of an electrically conductive material and is connected to a metering device by a tubing, and is for transferring a predetermined volume of liquid each time from a primary container to a secondary container. The transport device is for the controlled transport of the pipetting needle in three directions at right angles to one another, two of the transport directions extending horizontally and the third transport direction extending vertically. The control device is for controlling the metering device and the transport device. For the purpose of testing the linearity of the pipetting needle the analyzer includes a device for guiding the tip of the pipetting needle around the periphery of the top edge of a reference body (the tip of the pipetting needle is guided at a specific distance from the top edge of the reference body, which distance is a measure of the acceptable curvature of the pipetting needle), and an electrical circuit for detecting electrical contact between the tip of the pipetting needle and the reference body.

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Reutlingen, Switzerland

Thomas Caratsch