The common application, often referred to as Run Up/Run Down, is used to survey a machine’s dynamic response when the operating RPM is varied across the entire operating span. In this case, the RPM can range from a few RPM to 10,000 RPMs. Such tests are performed on automotive or aircraft engines and when commissioning new or refurbished stationary processing equipment. The measurements can be any physical quantities such as sound, displacement, velocity, acceleration, torque, etc. The analysis measure can be the amplitude or the power of an order, the energy over a fixed frequency band, a bin of octave filter, etc. The most important result for this type of measurement is the magnitude of the response versus RPM.
Another common application is monitoring measured machine displacement, velocity, acceleration, pressure, current or sound while the machine is performing its normal duty. The data acquisition system measures the amplitudes of specific orders and their phase relative to a reference tachometer input signal. The phase is calculated relative to the tachometer input or a separate reference input. This application is common for machine diagnosis and balancing. In this case, the operating RPM is relatively stable. Order tracking technology is useful to increase the accuracy of the estimation of orders.
Order Track signals with phase are useful in the study of rotating machines during Run Up/Run Down. This is often presented as a Bode Plot, useful in characterizing resonance/excitation intersections. The Bode Plot is a concept borrowed from control theory. It provides simultaneous Amplitude and Phase data over a changing speed range.
