| Abstract | An investigation is described in which a determination was made of the length equation of a four-metre invar rule used as a basis for measuring tapes. A short description of the rule and its associated apparatus is given. The investigation demonstrated that different rules made at the same time from the same ingot of invar do not necessarily have identical thermal coefficients. It was also found that the temperatures of two rules of different cross section differed considerably even in a room where the air temperature was changing only at a very slow rate i.e., 1 °C. in two or three hours. |
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