Abstract:
This paper describes a mechanical method for calibration of steel length measuring tapes with a hook or hook-ring and
lengths up to 10 m. A reference and a test tape are laid horizontally
by a series of horizontal supporters. In the measuring process the
reference standard tape is moved with respective to the test tape by
rotating a micrometer head. This movement is measured by a digital
dial gauge. The tension weights are used to stretch out the tapes up
to appropriate tensions. The tapes are properly clamped at the other
end of the system against the pulling force of tension weights. The
coincidence of scale marks is done by viewing the image of a CCTV
camera which is coupled with a monitor. The temperature of the two
tapes is measured to account the temperature effect. The deviation
in length from the zero of the test tape is measured by considering
temperature correction and sag correction. The performance of the
system was checked with a pre-calibrated steel tape and results
from the system are in agreement with the calibration certificate
of the test tape. A method to estimate the combined uncertainty of
the deviation in length calculated by the proposed method is also presented
