Bearing & Gearbox Vibration Analysis using Demodulation Techniques? (Part 2)

In our previous post on this subject we briefly looked at how we can use the detailed design information of bearings and gearboxes to look for specific fault conditions by collecting vibration information and analysing their frequency spectra. Amplitude modulation of the vibration signatures is common and we have seen how this causes side-bands to be present in the frequency domain.

(more…)

Continue ReadingBearing & Gearbox Vibration Analysis using Demodulation Techniques? (Part 2)

Bearing & Gearbox Vibration Analysis Using Demodulation Techniques (Part 1)

Bearings and gearbox vibration are fundamental issues for rotating machines in many industrial applications. These are critical components and, as such, any failure can prove expensive in both repair cost…

Continue ReadingBearing & Gearbox Vibration Analysis Using Demodulation Techniques (Part 1)

What Is A Hammer Test Or Hammer Impact Test?

This is often also known as Modal Testing. It is a method of testing that allows us to calculate the natural frequencies (modes), modal masses, modal damping ratios and mode shapes…

Continue ReadingWhat Is A Hammer Test Or Hammer Impact Test?

Do Missing Tachometer Pulses Mean The End Of The Road For Your Test?

Creating a good quality tachometer signal is one of the hardest parts of analyzing rotating machinery. So what happens if we have missing tachometer pulses? The data looked great until we tried to perform some in-depth torsional vibration analysis. And now we no longer have the component or vehicle to retest it.  Do we have to scrap the whole test? Was all that time wasted? Not necessarily…

(more…)

Continue ReadingDo Missing Tachometer Pulses Mean The End Of The Road For Your Test?
Read more about the article Everything You Ever Wanted To Know About GPS But Were Afraid To Ask
Figure 4: Differential GPS (DGPS)

Everything You Ever Wanted To Know About GPS But Were Afraid To Ask

As you may know Prosig have recently released a GPS module for their popular P8000 series of data acquisition systems. The GPS module adds the ability to record accurate position information alongside all of the normal measurement channels. This is a highly useful capability and enables an engineer to easily correlate measured results with vehicle position and behaviour at the time. It also makes it simple to extract data based on position on a test track or road course.

(more…)

Continue ReadingEverything You Ever Wanted To Know About GPS But Were Afraid To Ask

How To Analyze & Measure Torsional Vibration

Torsional Vibration MeasurementKnowing how to measure torsional vibration is of key importance in the area of vehicle development and refinement. The main contributory source is the engine where periodically occurring combustion cycles cause variation in the crankshaft rotary vibration. This vibration is transmitted to and modified further by other components in the powertrain such as the gearbox and by other equipment driven off the drive belt or chain. Additional torsional vibrations are also likely to appear downstream at the drive shafts and wheels.

(more…)

Continue ReadingHow To Analyze & Measure Torsional Vibration

Standard Octave Bands

The “standard” centre frequencies for 1/3 octave bands are based upon the Preferred Numbers. These date from the 19th century when Col. Charles Renard (1849–1905) was given the job of improving captive balloons used by the military to observe enemy positions. This work resulted in what are now known as Renard numbers. Preferred Numbers were standardised in 1965 in British Standard BS2045:1965 Preferred Numbers and in ISO and ANSI versions in 1973. Preferred numbers are not specific to third octave bands. They have been used in wide range of applications including capacitors & resistors, construction industry and retail packaging.

(more…)

Continue ReadingStandard Octave Bands

What Is A Fourier Transform?

A Fourier Transform takes a signal and represents it either as a series of cosines (real part) and sines (imaginary part) or as a cosine with phase (modulus and phase form). As an illustration, we will look at Fourier analysing the sum of the two sine waves shown below. The resultant summed signal is shown in the third graph.

(more…)

Continue ReadingWhat Is A Fourier Transform?