This in-depth presentation of current analytical methods for optimal design, selection, and evaluation of instrumentation for process plants is clear, concise, and systematic - providing a valuable tool for improving quality, costs, safety, loss prevention, and production accounting. The author concentrates on the tasks of determining the optimal set of measured variables and selecting the accuracy and reliability of the corresponding instruments. The goal is to obtain sufficiency accurate and reliable estimates of variables of interest while filtering bad data due to possible instrument malfunction. An additional goal is to observe and diagnose single and multiple process faults. It is an organized collection of the most relevant work in this area written to be readable by engineers with some background in linear algebra, mathematical optimization and graph theory. It is organized so that the complexity of the sensor network design is addressed step by step.