Patent ID: 7805281

Claim:
A method of deriving multiple types of vibration signals from one vibration signal for vibration analysis, the method comprising the steps of: measuring the vibrations of an object using at least one vibration sensor, wherein the vibration sensor converts vibrations into an electrical vibration signal; digitising the electrical vibration signal based on a first frequency, wherein the first frequency is selected from a plurality of possible frequency values and is an upper cut-off frequency; deriving a first type of vibration signal from the digitised vibration signal, wherein the first type of vibration signal is a high frequency waveform of the digitised vibration signal; deriving a second type of vibration signal from the digitised vibration signal based on a second frequency, wherein the second frequency is rationally determined from and lower than the value selected for the first frequency and is a lower cutoff frequency, the second type of vibration signal being a low frequency waveform of the digitised vibration signal; deriving a third type of vibration signal from the digitised vibration signal based on the second frequency and a third frequency, wherein the third frequency is rationally determined from and lower than the value selected for the first frequency and is a demodulation cut-off frequency, the third type of vibration signal being a demodulation waveform of the digitised vibration signal, said step of deriving a third type of vibration signal comprising the steps of: high-pass filtering the digital vibration signal at the demodulation cut-off frequency to produce a filtered signal; detecting the envelope of the filtered signal to produce an envelope signal; reducing the frequency of the envelope signal to at least approximate a frequency rationally determinable from and lower than the first frequency using at least one decimation filter; buffering the reduced-frequency envelope signal; and emptying the contents of the buffer as the demodulation waveform of the digitised vibration signal; outputting the first type of vibration signal for analysis; and outputting the second type of vibration signal for analysis.