A review of the impact of component variation in the manufacturing processon variable area (VA) flowmeter performance

The quality of an instrument, and thus its ultimate accuracy, will clearly be critically affected by the nature of the manufacturing process. Followin g a brief description of the variable area (VA) meter, the production proce ss of one manufacturer is examined. The manufacture of the float, tube, sca le, the calibration of the instruments, and the computer systems for loggin g the production progress of each instrument are briefly considered. The equation of the VA meter can be analysed to determine the effect of com ponent variation on the meter's accuracy, and the derails of this calculati on are given in Appendix A. The values used for variation have been estimat ed to reflect the likely situation in the industry. The most common problems and the possible areas for future work on the deve lopment of these valuable instruments are reviewed. Finally, more general lessons have been drawn for instrument manufacture fr om this example. (C) 2001 Elsevier Science Ltd. All rights reserved.