Velocity output accelerometers are usually used in condition monitoring applications, where velocity is a much better parameter for judging the health of a machine. Doubling of velocity vibration equates to a doubling of the deterioration of the health of the machine. Velocity can also be used in lower frequency applications, where the acceleration amplitude of vibration is too small to measure and the velocity vibration maybe of a higher and more meaningful value. Velocity vibration accelerometers are only effective if the frequency of vibration is higher than 2 Hz, but ideally 5 Hz.