Precision Measurement of Average Video-Track Rates or Pitch Relations on Quadruplex Recorded 2-in Video Magnetic Tape

A method of making precision measurements of video-track rates or pitch relations on 2-in quadruplex recorded tape has been developed and has been used for several years. The proposed revision of ANSI Standard C98.6–1965 specifies for a tape, recorded at 15 in/s (38.1 cm/s), an average space between reference points on each fourth consecutive track of 0.062500 in (1.5875 mm) with a tolerance of ± 62 millionths of an inch (0.001575 mm) which amounts to a tolerance of very nearly ± 0.1 % of the track rate or pitch,* in an unstressed or relaxed condition. In attempting to make such measurements certain problems become immediately apparent: tracks made visible with carbonyl iron can be measured repeatedly to only about 0.001 in (0.0254 mm); and measurement of flexible tape to the accuracies specified is difficult if not impossible. A method has been devised to make the repeated measurements to within ± 0.01% of pitch by using a long piece of recorded tape and measuring the span occupied by a known number of tracks. The unstressed-condition dimensions are obtained from measurements at different known tensions and the results are extrapolated to the zero tension condition.

Print ISSN

0361-4573

Published

1972-08

Content type

Original Research

DOI

10.5594/J13497