CALIBRATION Erwin Pilch Prevessin Site, F CERN CEDEX, FrancUniversity of Technology Graz, Austria 9 th August

Positioning Metrology and Surveying Group EST Engineering Support & Technology Division European Organization for Nuclear Research

Building 926, Prevessin Site, F CERN CEDEX, Franc Office 3

Calibration base Calibration of lengths (interferometric bench) : Reference : interferometer (s < 0.1 µm). Carriage : manual or automatic mode. Calibrated instruments : invar wires, Electro-optical distance-meters (for constant & cyclic errors), passive or active linear gauges, engraved tapes, scale bars, leveling staves. 4

Emitter Receiver Mirror Phase lag Electrooptical Distance Meter Industrial Total Stations High precision motorized theodolite with integrated distance meter. Characteristics of the Leica Total Stations: integrated infra-red distance meter measures on prisms and retro- reflective tapes of various sizes allows to set any addition constant high accuracy Typical accuracy up to 120m 0.5mm / 0.02" absolute TDA 5005 Outgoing Signal Incoming Signal Distance 5

Interferometer LS FR BS MR PD C The laser interferometer is manufactured by Hewlett Packard and consists of a stabilized Helium Neon laser, (l = 632,8nm, output power 1mW), a remote interferometer prism with a fixed reflector, a mobile reflector, a receiver and a display unit. The laser beam is split in two parts by the beam splitter, one part is reflected back by the fixed reflector and the other by the mobile reflector. The two beams are recombined and reach the receiver where the phase difference is proportional to the distance traveled by the mobile reflector. 6

Trolley Reflector The motorized trolley can be moved manually or automatically. It supports two reflectors for the interferometer. This allows to calibrate many different systems. During a calibration, the ground and the rail do not show any significant deformation. (weight around 280kg) Microscope 7

Parts of the installation Temperature sensorPrismMirror Support No. 3Support No. 1 (Zero)Support No. 2 9

The whole calibration process is fully computer controlled for this instruments. The meteorological parameters are collected from digital sensors and automatically stored and used to correct distances throughout the operation. Program at the base 10

Program - Calibration 2001 Opens a selected file and sorts the data. Example 50m–1m  1m–50m This function double the points in the area were there are fewer points. Plots a comparison between Fourier series and the data. Calculates points and lines with the parameters. Linear Regression, … Fourier Series, …. Connects two files with interpolation between the points. based on Etalonnage.m by Sara Poncet 11

Screenshots - Calibration 2001 Input dataOk! Error! Choose! Results! 18

Thanks... Thanks to my colleges Special Thanks to my supervisor Jean-Pierre Quesnel, and my college André Mathieu Thank you for listening. Thank you to Seamus Hegarty Karine Joasset Ricarda Betzing Ingrid Schmid 20