Tus pas ntsuas qhov siab uas yog lub voj voog telescopic insulating yog calibrated raws li metric scale. Tus pas ntsuas tseem ceeb yog ua los ntawm cov iav fiber epoxy muaj zog heev. Cov khoom no muaj cov khoom siv hluav taws xob thiab tshuab zoo heev. Tus pas ntsuas qhov siab no tsis hnyav thiab yooj yim siv, nws tuaj yeem ntsuas qhov siab ntawm cov xov hluav taws xob saum toj kawg nkaus thiab cov xov tooj sib txuas lus los ntawm hauv av. Kev calibration ntawm qhov chaw ntawm cov khoom yog qhov tseeb thiab raug, thiab qhov yuam kev ntsuas tsis tsawg dua 5cm.