DEVELOPMENT OF A LARGE MASS WEIGHT EXCHANGER

摘要

Top pan electronic comparators, which are widely used in National Measurement Institutes and mass calibration laboratories, for large mass calibration, inherently suffer from eccentricity and hysteresis. NPL has taken a commercial 60 kg comparator and designed an automatic weight exchanging mechanism to overcome these problems. This has been achieved by using a self centring scalepan with two weighing stations and exchanging between these two stations whilst maintaining a constant load on the comparator. This paper outlines the initial assessment of the commercial comparator, describes the conceptual design of the weight exchanger, and comments on the improved performance observed from the comparator with the exchanger. The paper also discusses the work currently in progress on a second generation weight exchanger, scaling the project up to 500 kg, incorporating modifications to overcome the problems found in the 50 kg weight exchanger.