Vibration analysis systems are used for vibration testing and modal analysis. They include instrumentation for acquiring data and analyzing results. There are two types of vibration: forced and resonant. Forced vibration can be due to internally generated forces, imbalances, external loads, or ambient excitation. A vibration analysis system receives detailed signals, including levels of single frequencies, often in high frequency areas. In most cases, the results of the vibration testing are monitored over a long period of time to observe the development of wear. The reliability of vibration analysis systems depends on credible and stable recordings, and the certainty that measured frequencies and amplitudes are correct.