The safe operation and efficient control of a nuclear power plant requires reliable information about the state of the process. Therefore, the validity of sensors that measure the process variables is of great importance. Properly validated process signals are also beneficial from the standpoint of increased plant availability and reliability of operator actions. Signal validation is implemented by using various algorithms. The effectiveness of a few other techniques during steady-state and transient-operating conditions are investigated. These algorithms are implemented in a personal computer-based system, along with a fuzzy logic decision-making module. The effectiveness of the overall system is demonstrated using data from operating power plants.