While the thrust of all the foregoing chapters has been toward understanding the underlying principles of instrumentation, and control of the process, it is inevitable that, for the best results, very great dependence has to be placed on the signals related to the various process parameters that the measuring/transmitting and control instruments, located in the plant or control room, generate or receive. The following comments are made with the objective of providing both readers of this book and users of the instrumentation the most meaningful control system, and the information given is primarily concerned with the installation of instrumentation in the field, and, where necessary, the implications that control and computational functions have on the operation of the process plant. Without a good measurement—and by that is meant a truly representative and repeatable one—the control of the process will almost certainly always be poor. The topics discussed in this chapter are intended to help in developing an ability to recognize and avoid the hazards that could be encountered, and to be of assistance when designing a control system. This newly found expertise when coupled with correct installation would help produce meaningful signals.