Sensors: the first stage in the measurement chain

In the first (Fowler and Schmalzel,vol.7,no.1,pp.38-46,Mar. 2004), the context for the tutorial articles was set up by addressing the question of why we measure. Hence many of the common sensor strategies that constitute the first stage in the measurement chain are introduced. While every element of that chain is important, the choice of an appropriate, robust sensor is one of the critical decisions that must be made. This article, the second within the tutorial series, will continue to use examples from test stands for testing rocket engines. Measurements of the weight of liquids, their temperatures, and their flow rates in these rocket engine test stands require sensors and the understanding of how to use them.