Posted ByDuncan Carter on July 31, 2003 at 08:45:45:
In Reply to: envelope posted byzhaotao on July 30, 2003 at 05:12:37:
: Dear Carter:
: sorry to trouble you again,
: 1/my question is: when I get a spectrum plot(10~5000Hz,the range of the transducer), in some areas there may be high ampltitudes, for example , in the band 1000~2500Hz and band 3500~5000Hz at the same time, but in the other area, the plot is "flat",How could I know that which is excite by the friction force? and which is the natural frequency of the bearing? which area should I use, the flat or high apmltitudes area?
You should use a flat area. In most cases except for low shaft rotating frequencies, this is an area above 5 KHz. DREAM for Windows automatically calculates and selects a suitable frequency range based on the bearing dimensions and shaft rotating frequency.
: 2/could you please send me some information about the prime knowlwdge about the enevlope method use the "flat area", for the envelope process of the natural frequency is easy to understand, but not for the "friction".
: 3/Is there some different of the envelope results if we use the diferent method? Now I have two different instrment, one use the 36KHz bandpass filter, the other use the Hilbert transform in the software on the PC
The demodulation method should not affect the results but in practical applications, different manufacturer's filter methods can effect the results so that you are likely to get different results on different instruments.