Land survey precision tape calibration.
Proper use of measuring tapes (we call them chains) for precision work requires temperature correction and specific tension. Basic steel tapes have a coefficient of thermal expansion (CTE) of approx. 12 ppm per deg C.
Calibration tapes are made of Invar, and a similar alloy commercially sold as Lovar. These alloys have a CTE of about 1 ppm (?) per deg C.
Q: what is the true (accepted/published) CTE of 36Ni/64Fe steel (Invar)?
Q2: what is the CTE and composition of Lovar?
I have a K&E Lovar 100 foot 'standard' tape. (It has only 3 marks (0, 50, and 100).)
What I have found re: CTE of Lovar is anywhere from 0.5 to 5 ppm per deg. Some cite better than Invar, some say an economical alternative to Invar, or not as good as Invar, or somewhere in between Invar and steel.