signal processing Archive
Amplitude And Energy Correction – A Brief Summary
Posted on September 1, 2009 | 8 CommentsAmplitude and energy correction has been and is a continuing point of confusion for many people calculating spectra from time domain signals using Fourier transform methods. The first thing to...
Data Windows : What, why and when?
Posted on July 20, 2009 | 7 CommentsBefore we discuss the use of data windows, we should first remind ourselves of three basic properties of the FFT (Fast Fourier Transform) process. First, energy information in signal must...
Interpolation Versus Resampling To Increase The Sample Rate
Posted on June 22, 2009 | 4 CommentsThese are two different techniques aimed at different objectives. First consider a simple sinewave that has been sampled close to the Nyquist frequency (sample rate/2). Visually this looks very pointy. We...
Measurement And Analysis Of Torsional Vibration
Posted on October 17, 2008 | 13 CommentsTorsional 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...
Shaft Displacement Measurement Using A PROTOR System
Posted on June 4, 2008 | 6 CommentsShaft displacement is an important vibration measurement for rotating machines. Shaft displacement is usually monitored by non-contact shaft displacement probes such as eddy-current probes. These probes produce a voltage proportional...
What Are dB, Noise Floor & Dynamic Range?
Posted on April 14, 2008 | 9 CommentsMost engineers are probably familiar with or have come across the decibel or dB as a unit of measurement. Its most common use is in the field of acoustics where...
Vibration Monitoring Phase Measurement And The Tacho Signal
Posted on March 4, 2008 | 5 CommentsAny vibration signal may be analyzed into amplitude and phase as a function of frequency. The phase represents fifty percent of the information so it is most important to measure...
Human Exposure To Vibration In Buildings (DIN 4150-2:1999-06 & DIN 45669-1:1995-06)
Posted on November 30, 2007 | 4 CommentsStandards DIN 4150-2:1999-06 and DIN 45669-1:1995-06 provide a means of assessing the effect on human beings of vibration caused by vehicle traffic, trains both above and below ground, construction work...Orders v Time – Comparing Overall Levels
Posted on October 23, 2007 | 4 CommentsBy combining a speed signal with a data signal and using the Short Time FFT algorithm (Hopping FFT), it is possible to extract order data directly as a function of...
Calculating Velocity Or Displacement From Acceleration Time Histories
Posted on October 5, 2007 | 13 CommentsIt is quite straightforward to apply “classical” integration techniques to calculate either a velocity time history from an acceleration time history or the corresponding displacement time history from a velocity...
Sound Steering
Posted on September 12, 2007 | No CommentsThe requirement was to develop a ‘standard’ test for assessing the sound quality of power steering pumps in vehicles. Measurements needed to be objective so that the method would be...Measuring Torsional Crank Shaft Jitter
Posted on June 24, 2007 | No CommentsUsing Prosig’s P8000 series data acquisition system with DATS signal analysis software, torsional analysis (crank jitter) was performed on an automotive engine attached to an engine dynamometer. The significance of...
What Is Resonance?
Posted on May 23, 2007 | 23 CommentsFirst, in order to explain resonance we have to explain the terms we will use. - A period is the amount of time it takes to complete one cycle -...Evaluating A Closed Loop Control System For High Pressure Pumps
Posted on March 29, 2007 | 1 CommentProsig were recently involved in the validation of a closed loop control system for an automotive pump supplier. The customer has a large number of test cells, each test cell...Order Cuts And Overall Level
Posted on February 25, 2007 | No CommentsOrder cuts are taken from a set of FFTs, each one at a different rpm. The rms level is then found as the Square root of the Sum of the...
Acceleration, Velocity & Displacement Spectra – Omega Arithmetic
Posted on December 7, 2006 | 18 CommentsAccelerometers are robust, simple to use and readily available transducers. Measuring velocity and displacement directly is not simple. In a laboratory test rig we could use one of the modern...
Examples Of Event Extraction And Removal
Posted on November 9, 2006 | 1 CommentIn many cases only significant events, such as bumps or other transients in a signal are of relevance. The objective is to be able to isolate these events in a...
Measuring For Success
Posted on September 11, 2006 | No CommentsThe following application note shows the steps taken to perform a structural analysis on an automotive exhaust pipe structure with the aim of improving the structural damping properties of the...
Fatigue & Durability Testing
Posted on May 17, 2006 | 10 CommentsThe following application note describes the test and measurement process for the fatigue testing and development cycle of an automotive suspension component, specifically a tie rod. The component had been...
Exhaust Development Using A Prosig P8000 System
Posted on February 20, 2006 | 2 CommentsThe following note describes an application of the Prosig P8000/DATS system in the refinement of an automotive exhaust muffler design for a major after-market exhaust manufacturer in Europe. The particular...
Standard Octave Bands
Posted on February 17, 2006 | 6 CommentsThe “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...Torsional Vibration, Tacho Pulses And Aliasing
Posted on January 12, 2006 | 4 CommentsWith shafts, gears and the like, the general method of determining the rotational speed is to use some form of tachometer or shaft encoder. These give out a pulse at...
Analyzing Shaft Twist And Repairing Damaged Tachos
Posted on October 19, 2005 | 1 CommentA shaft has been instrumented with two shaft encoders, one at each end. Each shaft encoder gives out a once/rev pulse and a 720 pulses/rev signal. Each signal was digitised...
Phase Between Signals
Posted on August 9, 2005 | 4 CommentsThe following article was written in response to a question from a visitor to the website. The gentleman in question had been reading some of the Prosig signal processing articles...Average Waterfalls Or Average Orders?
Posted on June 14, 2005 | No CommentsOne would expect that averaging waterfalls and then extracting orders would give the same result as extracting orders from individual waterfalls and then averaging them. This is not the case.
