Line standards such as measuring tapes and rules still form a major component in the traceability chain for dimensional metrology. The calibration or verification of these standards is carried out in order to check whether they comply with the classes given in OIML standards or with the user specifications. 5 m-measurement system was constructed by UME for calibration of workshop rules and tapes up to 5 m long. The system is mainly composed of 6 m rail system, mechanical parts and optical units. The rails are kinematically located on a heavy marble construction and a carriage, which employs a camera for probing of the scales on the tapes, is moved a long the rails during the measurement. The image of the scale taken by the camera is viewed on the monitor screen together with software. The operator can perform the probing process by simply placing the measured scales on the viewed target with the help of an X-Y table located on the carriage. The X-Y table and the carriage movement are measured by a 6 m incremental linear encoder integrated to the system or optionally by a laser interferometer. The measurement values are transferred to the computer for evaluation according to OIML standards. The developed software running in windows environment also performs temperature measurement for required corrections. The software automatically takes the measurement results from either incremental linear encoder or laser interferometer, depending on the option chosen in the software) and processes it for representation to the user. The overall uncertainty for the system with the linear encoder is U = [(0.05)~2+ (0.005L)~2]~(1/2) mm, where L is measured length of the tape or rule in meters.
展开▼
