A motorized 5 m tape comparator for traceable measurements of tapes and rules Tanfer Yandayan ⇑ , Bulent Ozgur TUBITAK UME, Barıs Mah. Dr. Zeki Acar Cad. Pk54, 41470 Gebze/Kocaeli, Turkey article info Article history: Received 3 April 2013 Received in revised form 4 July 2013 Accepted 25 November 2013 Available online 4 December 2013 Keywords: Material measures Legal metrology Line standard Surveying tape Rule Length comparator abstract A motorized 5 m tape comparator was constructed in TUBITAK UME for calibration of tapes and rules up to 5 m length in one set-up and further lengths in multiple set-ups. The sys- tem is a practical development and provides a cost effective solution for calibration of tapes in which the highest grade’s accuracy requirement in OIML R35-1 e.g. is 600 lm for 5 m length and 1100 lm for 10 m length. It is mainly composed of 6 m rail system, mechanical parts, optical units and an integrated 6 m incremental linear encoder as a reference mea- surement axis for traceable measurements. The rails are kinematically located on a heavy marble construction and a motorized carriage, which employs a camera for probing of the scales on the tapes, is moved along the rails during the measurement. The image of the scale taken by the camera is viewed on the monitor screen together with the running soft- ware. The operator can perform the probing process by simply moving the carriage over the measured scales (tapes or rules) using a joystick. The carriage movement is measured by the incremental linear encoder previously calibrated by a laser interferometer and the software automatically takes the measurement results from the incremental linear enco- der, applies correction values previously defined and determines the length of the tapes and rules as well as deviations from nominal lengths. The estimated expanded uncertainty of the steel tape measurement is U = 54 lm in one set-up (for 5 m length) and U = 77 lm in two set-ups (for 10 m length) at the confidence level of approximately 95%. Uncertainty budget for calibration of the device itself and for calibration of the test tapes are explained in detail. The results of extensive experimental work and analysis are provided by demon- strating application of science and technology of measurement and instrumentation. Inves- tigations for long term stability of the system are given with the reported test results for the years of 2003-2011 and participated intercomparison results to validate the device sci- entifically are illustrated. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Line standards such as measuring tapes and rules still form a major component in the traceability chain for dimensional metrology particularly in legal metrology, in surveying applications and engineering workshops. The calibration or verification of these standards is carried out in order to check whether they comply with the classes given in OIML recommendations [1] or with the user spec- ifications. OIML R35 series [1] give set of recommendations for the type evaluation and initial verification testing of material measures of length for general use as well as the specifications of the classes. European standards and direc- tives of 73/362/EEC specify the accuracy classes of the tapes for European market [2]. Recently, ASME B89.1.7 ‘Performance standard for steel measuring tapes’ has been launched as a draft document to give guidance about 0263-2241/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.measurement.2013.11.040 ⇑ Corresponding authors. Tel.: +90 262 6795000x5312 (T. Yandayan). Tel.: +90 262 6795000x5306 (B. Ozgur). E-mail addresses: tanfer.yandayan@tubitak.gov.tr (T. Yandayan), bulent.ozgur@tubitak.gov.tr (B. Ozgur). Measurement 49 (2014) 113–125 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement