Abstract: A study on the performance of an extra-long measuring bar used for non-contact measurement of inner diameter and geometrical form in a long tube is reported in this paper. A method of pre-bending the measuring bar for compensating its elastic deflection is proposed. Thus, a straight measuring bar can be used to carry a sensor for accurate and steady data acquisition. Secondly, to avoid or reduce the effect of environmental vibration, the natural frequencies of measuring bar with two kinds of loads are analyzed, and a suggestion to reduce that effect is given in this paper. The research results are of universal significance for the design of various extra-long measuring bars.

Key words: natural frequency, measuring bar, deflection