## 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.

## 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…

## How do we design or modify a system to avoid resonance?

After finding the natural frequency of a system, what could be done to stop or reduce the systems resonance being excited? Basically put, how do we avoid resonance This is…

## Three Methods For Analyzing Vibration In Rotating Components

In this post we will first look at how to process data from rotating machinery. Then we will focus on shaft or gear train twist. Let's look at 3 different…

## Beyond The Sound Level Meter

Have you reached the limits of your Sound Level Meter? Do you need to progress to the next level? Prosig have a range of systems that can increase your noise…

## Prosig Seminar in Hiroshima, Japan on the 3rd & 4th December, 2013

Prosig and their partners, SV Japan, will be holding a two-day training seminar for current and new customers in Hiroshima on Tuesday 3rd and Wednesday 4th December 2013. Subjects covered…

## A Method Of Diagnosing Cyclic Events In An Internal Combustion Engine

A method to identify subjectively objectionable disturbances (e.g. piston slap, valve tick,… etc) in internal combustion engines

## Generating speed v time information from noise & vibration signals

Picture the scenario; you have captured some noise & vibration data from a rotating machine. Typically, this might be noise in a vehicle cabin, but could have been anything from…

## Understanding Phase Measurements

When performing frequency analysis of vibration data for any application the resultant spectrum has both amplitude and phase components, therefore the phase component represents half of the information available and…

## What Is Resonance? (Part 3)

In the previous two articles (What Is Resonance? (Part 1) & What Is Resonance (Part 2)) in this series we have looked at how we can identify a resonant frequency.…

## A Guide To Digital Filtering

Understanding filters is actually simpler than it may first seem. Creating a filter is another story; it’s like being able to drive a car without having to know the intricate…

## A Different Way Of Averaging – Time Synchronous Averaging

Assuming one wants a frequency spectrum from an acquired time measurement, it is generally accepted that averaging of a signal in the time domain is not very useful due to…

## What Can I Do About Spikes In My Data?

Whether you call them spikes, glitches, anomalies or data dropouts, these phenomena have been a problem to engineers ever since they started recording data. There are any number of reasons…

## Video: How To Calibrate Microphones & Accelerometers

Here are two videos on a relatively simple, but sometimes misunderstood procedure – how to calibrate microphones & accelerometers (more…)

## A Simple Capture, Analysis and Report (Part 4)

http://www.youtube.com/watch?v=vZCKb4ikX1s This is the final part of our four part tutorial. This adds a report to the worksheet we developed in part 3.

## A Simple Capture, Analysis and Report (Part 3)

http://www.youtube.com/watch?v=gvwwfCampas Today we have the third of our four part tutorial. Here we show how to quickly build a worksheet to analyze the data we captured in parts one and…

## A Simple Capture, Analysis and Report (Part 2)

http://www.youtube.com/watch?v=4ejGBG5ImfY Part two of the four tutorials showing a simple setup to capture, analyze and produce a report using Prosig’s DATS software and P8000 hardware. This part deals with setting…

## A Simple Capture, Analysis and Report (Part 1)

http://www.youtube.com/watch?v=dGRzTxzUWfE The first part of a series of four tutorials showing a simple setup to capture, analyze and produce a report using Prosig's DATS software and P8000 hardware. Part 2…

## How Can Social Networks Help Engineers?

Over the past few years it has been impossible to ignore the rise of social networking. Sites such as Facebook & Twitter have come to dominate the Internet to such…

## 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…

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.

## How To Analyze & Measure Torsional Vibration

Knowing 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.

## 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.

## 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.

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