GB2157449A - Analysis of vibration - Google Patents

Abstract

There is disclosed a method and apparatus for subjecting vibration from a machine part P to Fourier analysis using a spectrum analyser. The vibration is sampled at timed intervals and the amplitude of each sample is digitally recorded. The timed intervals correspond with the sampling intervals of the spectrum analyser whereby redundant data is not recorded. A solid state memory M may be used to store the amplitude of the sampled signals from transducer T. <IMAGE>

Description

SPECIFICATION Analysis of vibration This invention concerns a method and apparatus for the analysis of vibration.

A conventional method for analysing vibration in a moving machine comprises the steps of securing a transducer sensitive to vibration such as an accelerometer or a strain gauge to the machine and passing the signal therefrom to an instrumentation tape recorder. Subsequently the tape from the recorder is played back into a spectrum analyserwhich samples the signal at appropriate timed intervals to enable a Fourier analysis to be effected.

This method suffers from the disadvantage that the tape recorder can prove unreliable in hostile environments and is prone to signal degradation.

Attempts to overcome this problem have included recording the vibration digitally. A problem here is that an extraordinary large memory is necessary to capture even a short duration of signal. For example, some 64 kilobytes of memory are necessary to record a signal of some half second duration. Also, the analysis of such a large amount of data is time consuming and expensive.

The present invention provides a method for analysing vibrations that is not subject to the aforesaid disadvantages.

Thus according to the present invention, a method of Fourier analysing vibrations using a spectrum analyser comprises the steps of sampling the vibration and digitally recording the amplitude thereof at timed intervals equal to the sampling intervals of the said spectrum analyser.

Preferably the digital signals are recorded in a solid state memory device.

The invention will be further apparent from the following description, with reference to the single figure of the accompanying drawing, which shows, by way of example only, a block circuit diagram of apparatus for carrying out the method of the invention.

Referring now to the drawing, it will be seen that a transducer T capable of measuring vibrations is secured to a machine part P whose performance is to be monitored. The output from the transducer T is fed through line 1 to data processing equipment D including solid state memory M and circuitory C adapted to sample the signal from the transducer T at timed intervals and record the amplitude of each sample digitally in the memory M.

After a period the recording apparatus D can be removed and taken to a spectrum analyser which will read in data from the memory M and Fourier analyse the data.

The timed intervals for recording the data are chosen to correspond to the intervals employed in the spectrum analyser.

It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof as defined by the appended claims.

1. A method of subjecting vibration to Fourier analysis using a spectrum analyser comprising the steps of sampling the vibration and digitally recording the amplitude thereof at timed intervals corresponding with the sampling intervals of said spectrum analyser and reading the recorded data into the spectrum analyser to enable the Fourier analysis to be performed.

2. A method according to claim 1 wherein the digital signals are recorded in a solid state memory device.

3. Apparatus for collecting data concerning vibration to be subjected to Fourier analysis using a spectrum analyser comprising a transducer adapted to be mounted to be responsive to said vibration and data processing equipment adapted to sample the output from said transducer and digitally record the amplitude thereof in a memory device at timed intervals corresonding with the sampling intervals of the spectrum analyser.

4. Apparatus according to claim 3 wherein said memory device is comprised by solid state memory.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Analysis of vibration This invention concerns a method and apparatus for the analysis of vibration. A conventional method for analysing vibration in a moving machine comprises the steps of securing a transducer sensitive to vibration such as an accelerometer or a strain gauge to the machine and passing the signal therefrom to an instrumentation tape recorder. Subsequently the tape from the recorder is played back into a spectrum analyserwhich samples the signal at appropriate timed intervals to enable a Fourier analysis to be effected. This method suffers from the disadvantage that the tape recorder can prove unreliable in hostile environments and is prone to signal degradation. Attempts to overcome this problem have included recording the vibration digitally. A problem here is that an extraordinary large memory is necessary to capture even a short duration of signal. For example, some 64 kilobytes of memory are necessary to record a signal of some half second duration. Also, the analysis of such a large amount of data is time consuming and expensive. The present invention provides a method for analysing vibrations that is not subject to the aforesaid disadvantages. Thus according to the present invention, a method of Fourier analysing vibrations using a spectrum analyser comprises the steps of sampling the vibration and digitally recording the amplitude thereof at timed intervals equal to the sampling intervals of the said spectrum analyser. Preferably the digital signals are recorded in a solid state memory device. The invention will be further apparent from the following description, with reference to the single figure of the accompanying drawing, which shows, by way of example only, a block circuit diagram of apparatus for carrying out the method of the invention. Referring now to the drawing, it will be seen that a transducer T capable of measuring vibrations is secured to a machine part P whose performance is to be monitored. The output from the transducer T is fed through line 1 to data processing equipment D including solid state memory M and circuitory C adapted to sample the signal from the transducer T at timed intervals and record the amplitude of each sample digitally in the memory M. After a period the recording apparatus D can be removed and taken to a spectrum analyser which will read in data from the memory M and Fourier analyse the data. The timed intervals for recording the data are chosen to correspond to the intervals employed in the spectrum analyser. It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof as defined by the appended claims. CLAIMS

1. A method of subjecting vibration to Fourier analysis using a spectrum analyser comprising the steps of sampling the vibration and digitally recording the amplitude thereof at timed intervals corresponding with the sampling intervals of said spectrum analyser and reading the recorded data into the spectrum analyser to enable the Fourier analysis to be performed.

2. A method according to claim 1 wherein the digital signals are recorded in a solid state memory device.

3. Apparatus for collecting data concerning vibration to be subjected to Fourier analysis using a spectrum analyser comprising a transducer adapted to be mounted to be responsive to said vibration and data processing equipment adapted to sample the output from said transducer and digitally record the amplitude thereof in a memory device at timed intervals corresonding with the sampling intervals of the spectrum analyser.

4. Apparatus according to claim 3 wherein said memory device is comprised by solid state memory.