Precise linear measurements using a calibrated reference workpiece without temperature measurements

We suggest a procedure for the correction of the errors caused by thermal expansion of a workpiece and the scale of a linear measuring instrument (coordinate measuring machines, length measuring machines, etc.) when linear measurements are performed at nonstandard temperature. We use a calibrated reference workpiece but do not require temperature measurements. An estimation of the measurement uncertainty and application examples are given.

Desenvolvimento de material didático para uso em aulas práticas de metrologia industrial

<p>In the current economic scenario of the Brazilian federal universities, it is a great challenge to acquire high resolution and high accuracy equipment for use in metrology practical classes. As an alternative, it is common the development of projects aiming the design and construction of low-cost courseware equipment. They are built within extension activities involving graduation students. This paper reports the development of two pieces of equipment for use in practical classes of the discipline “Principles of Industrial Metrology”, of the Mechanical Engineering course at the Federal University of São Carlos (UFSCar). The activity was supported by the Extension Office (ProEx) and had, as a premise, the use of low-cost materials and manufacturing processes. Within the proposed scope, a universal measuring table and a linear measuring machine were developed. The constructive process allowed to verify that the exercise of simple practices is a motivating experience for the student who was directly involved in the activity and for the students who use the produced equipment.</p>

Application of Reflectorless Total Station in Bridge Detection and its Accuracy Analysis

In order to solve the problem of the linear measurement of arch ring for the detection of bridge,a new method is presented that measures the arch ring using a reflectorless total station on the side of the arch bridge and the detail operations are given. Taking account of weakness of edge suveying using a reflectorless total station,some formulas on the 3d coordinates calculation of the above and down edge of the arch ring based on the arch ring points are deduced.According to the law of error propagation, the accuracy of the X and Z axial coordinates are analysed.It is helpful for calculating lateral and vertical deformation and biridges elevation map that the transformation from free-station coordianates to the birdge axis coordinate by programming using EXCEL software is achieved.The method is used for bridges arch ring axial measurement in Qingcheng town,Yuzhong county,Gansu province,and its deformation is consistent with the measured results of the dial indicator,which satisfies the requirement of bridge detecton accuracy.So it is showed that the method is a good way of linear measuring of bridges arch ring.