Tape Correction, Sag Correction, Pull Correction and Temperature Correction
In this article, I will list out different formulas for the respective corrections…
The following corrections are to be made for measurements taken with a tape because tape can never be practically used under specified standard conditions.
Correction for absolute length
Absolute length of tape is its actual length under specified condition
Ca = Lc/L
Where, Ca = correction to be applied to the tape in ‘m’
Lc = measured length in ‘m’
L = nominal length of tape in ‘m’
Correction for temperature
Length of tape is increased with the increase of temperature and decrease with decrease of temperature.
Ct = A (Tm – Ts)
A = coefficient of thermal expansion per one degree Kelvin
Tm = temperature during the measurement in Kelvin
Ts = temperature at which the tape standardised in Kelvin
Correction for Sag
When the tape is suspended from two ends in air
Sag correction, Cs = L/24(W/P)2
Where, L = horizontal distance between supports in meters
W = weight of tape in Newtons
P = Pull applied in Newtons
Correction for Pull
If the pull during measurement in not the same at which the tape is standardised then the correction for pull is necessary.
Cp = [(P – P0)/AE) * L]
P = pull in Newtons
L = length of measured line in ‘m’
P0 = standard pull in Newtons
E = Young’s Modulus in N/mm2
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