3384. Measuring Weight And Center Of Gravity Using Load Cells

Paper

Abstract

Today?s load cells are capable of an accuracy of +-0.05%, or better, under ideal conditions. But ideal conditions are expensive to obtain and, because ?you get what you pay for,? these high accuracies are not always possible or even required. Given sufficient time and money most anything can be weighed to a high degree of accuracy. More often we are asked to measure the weight and center of gravity of an object when the design and building of specialized fixtures and laboratory conditions is not practical or warranted. To meet the needs of a customer without exceeding his budget we are often required to be creative in how we use the equipment available while keeping in mind the accuracy and validity of the data we are gathering. Many things will affect the accuracy of the information we get from a test, especially the quality of the equipment, the physical arrangement, our procedures and the calibration uncertainty of the load cells. There are just as many areas where confidence can be built into a test. To obtain the best value for the dollar from our test we must consider things like the set-up of the test, weight and dimensional measurements, environmental factors and equipment shortcomings. For the purpose of this paper the term ?load cell? refers to stand alone canister-type cells, like those in a standard aircraft weighing kit, that are not part of a permanent fixture. This type of equipment is commonly used to measure the weight and center of gravity of large parts, assemblies, tooling, missiles and other items where a unique set-up is required for each.