For laboratory weathering instruments to be most useful, they must have, among other qualities, the ability to conduct tests repeatably and reproducibility. Repeatability is the measure of a specific instrument's ability to duplicate results from one test to another. Reproducibility is the measure of the ability of instruments of the same model to duplicate test results. As users become more sophisticated, the demand for instruments capable of very good reproducibility and repeatability increases. Thus, instrument manufacturers are constantly challenged to deliver suitable instruments to the testing community. For those tests that are influenced by multiple parameters, some of which are synergistic, while others are offsetting, the challenge is even more pronounced.

This paper discusses the concepts and features incorporated in a particular type of xenon weathering instrument to control critical test parameters, whether they are mutually compatible or not.