Patent ID: 7585678
Filing Date: 2009-09-08
Classification: G01N,Y10T

Abstract:
1. A method for determining a reference position for a pipetting needle which is part of an automatic analytical apparatus which comprises a rotatable conveyor for conveying reaction cuvettes along a circular path, conveyor driving means for rotating said conveyor in a step-wise manner, an automatic pipetting unit having a pipetting needle for pipetting samples and reagents into said reaction cuvettes, thereby forming liquid sample-reagent-mixtures, level detection means for detecting contact of said pipetting needle with a liquid surface in a vessel or with a metallic part of the apparatus, and a reference member for determining a reference position, said method comprising: (a) a first measuring step for measuring a first displacement error (ΔX) in a displacement of said pipetting needle effected by said transport device along said straight line in said first direction (X-axis), said first error (ΔX) being caused by a corresponding first angular error (φ) of an initial angular position of said pipetting needle along said circular path determined by said excenter mechanism, said first measuring step comprising actuating the excenter mechanism of the pipette needle to bring the needle in contact with the reference member, (b) a first correcting step for correcting said first displacement error (ΔX) by means of a corresponding correction of said angular error (φ) of said initial angular position of said pipetting needle, (c) a second measuring step for measuring a second displacement error (ΔY) in a displacement of said pipetting needle in a second direction (Y-axis) perpendicular to said vertical plane, said second displacement error (ΔY) being caused by a corresponding second angular error (α) of an initial angular position of said pipetting needle along said circular path determined by said excenter mechanism, said second measuring step comprising actuating the excenter mechanism of the pipette needle to bring the needle in contact with the reference member, (d) a second correcting step for correcting said second displacement error (ΔY) by means of a corresponding change (α) of the angular position of said pipetting needle along said circular path, (e) a third measuring step for determining the position of a vertical reference line, said reference line being a line where said pipetting needle contacts a fixed first reference plane surface in the apparatus, said first plane surface lying in a plane (Y-Z) perpendicular to said straight line in said first direction (X-axis), and (f) a fourth measuring step for determining the position of a reference point (X0, Y0, Z0) along said reference line, said reference point being the point where the tip of said pipetting needle contacts a fixed second reference plane surface in the apparatus, said second reference plane surface lying in a plane (X-Z) perpendicular to said reference line.