National Instruments Order Analysis Toolset Order Analysis

Order Analysis

This chapter gives brief descriptions of the need for order analysis, the

basic concepts of order analysis, the effect of rotational speed on order

identification, and the different order analysis methods.

When it is impossible or undesirable to physically open up a system and

study it, you often can gain knowledge about the system by measuring and

analyzing signals associated with the system. For example, physicists and

chemists use the spectrum generated by a prism to distinguish between

different types of matter. Astronomers apply spectra, as well as the Doppler

effect, to determine distances between planets. Physicians use the

electrocardiograph (ECG), which traces the electrical activity of the heart,

as a nonsurgical means of diagnosing heart problems.

You can use order analysis to study, design, and monitor rotating

machinery. By measuring and analyzing sound or vibration signals

generated by a system with rotational components, you can gain a better

understanding of the system, associate features of noise and vibration

with the physical characteristics of the system, and identify system

characteristics that change with time and operating conditions.

Systems with rotational components include automobiles, airplanes,

airconditioners, and PC hard drives.

Order analysis and harmonic analysis have much in common. The term

harmonic refers to frequencies that are integer or fractional multiples of

af undamental frequency.

When dealing with rotating machinery, you often can hear noise and feel

vibration created by the parts associated with the rotating components.

Parts associated with rotating components include bearings, gears, and

blades. Vibration of the rotating components creates noise and vibration

signals. The machine rotational speed is the source of the noise and