please explain me difference between the harmonic and order.
when and why, they come into spectrum.

what is the significant of harmonic, yes i read in book, with harmonic we can predict the faults like misalignment, looseness,imbalance etc.
than what does it indicate if spectra showing 6X , 8X and higher integer.

thanks
vivek

quote:

please explain me difference between the harmonic and order.
when and why, they come into spectrum.

what is the significant of harmonic, yes i read in book, with harmonic we can predict the faults like misalignment, looseness,imbalance etc.
than what does it indicate if spectra showing 6X , 8X and higher integer.

Harmonics simply means a frequency peak an equal distance from a fundamental frequency peak that is measured from "0", but not necessarily the running speed peak of the shaft where the data came from. Any given frequency peak can have or not have harmonics.

Order can and is most of the time referring to running speed as one order and any frequencies within the given Fmax that are harmonics of running speed are consistered "orders" of running speed. But one can say "the 1st harmonic of this bearing is the 2nd order of the bearing fundamental defect frequency". Or "this peak is the 2nd order of gearmesh". Etc.

To decipher what 6X or 8X is, one has to take into consideration what could be going on inside the equipment. Is 6X vanepass, bladepass, or is 8X vanepass or bladepass or is 6x and 8x directly related to the actual 1X as in looseness?

A simple answer to what a specific harmonic or order of running speed is, is not always so simple.

Harmonics aid in the determination of the severity of a possible problem.

I see you did not mention sidebands, a very important signal pattern in a spectrum. Good that you understand them.

My favorite memo: Never assume anything or take anything for granted in analyzing a spectrum or waveform.

OMOAICBTW

quote:

please explain me difference between the harmonic and order.
when and why, they come into spectrum.

ORDER is just a unit of frequency. Frequency has three usable units:

1) Order
2) cpm
3) Hz = cps

So Frequency is a must in spectrums. Its your choice which unit to choose. Now assume that there is a motor which is running at 1500 rpm. Now you are using orders and I am using cpm.

So you will have 'running speed freuency' at 1X and I will have it on 1500 cpm. Second order will be at 2X and mine will be at 3000 cpm....and this will go on.

Now harmonics is just the multiples of the frequency selected.

-If I select 1500 cpm as a frequency and I tell my software to give me the multiples of 1500 cpm, than I will get 3000 cpm, 4500 cpm, 6000 cpm, 7500 cpm, and so on.....

Now you used order as your frequency unit, so you will simply get 2X, 3X, 4X, 5X, 6X, and so on.......

-Now select 4650 (1500 x 3.1) cpm as a frequency and I tell my software to give me the multiples of it, than I will get 9300 cpm, 13950 cpm, 18600 cpm, and so on.....

As you used order as frequency unit, so you will still get 2X, 3X, 4X, 5X, 6X, and so on.......


Its just that you have to know what your primary frequency is.....than you can manipulate easily.

This message has been edited. Last edited by: Zee-Vibe,

Thanks Ralph and Zee-Vibe for detailed and nice explanation.


regards
Vivek