The primary categories of measurements used in our monitoring systems are for fault detection and fault analysis & diagnosis.
Protective monitoring vibration measurements are for detecting changes just before a catastrophic failure, and are based on overall values. Condition monitoring vibration measurements are focused on early fault detection, and are "decoupled" from process influences. Process data, performance and other calculated parameters are also used for fault detection.
Fault analysis and diagnosis measurements together with plots and trending tools can help identify the nature and severity of the fault. For vibration diagnosis, frequencies, phase, sidebands and harmonics indicate the type and location of fault. Brüel & Kjær has in fact pioneered the development and use of several powerful diagnostic spectrum measurements such as the CPB, envelope and cepstrum. The versatile spectrum measurement is not only used on vibration, but also on current, noise and pressure. Even the raw time signal plays an important role in diagnosis and analysis.