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
[Video] Creating speed signals for data with no tacho
So you've got some noise and/or vibration data from a rotating machine, but no speed information. Surely that means you can't analyse against speed or do any order analysis, right?…
Building a new test model
Recently, we decided it was about time we had a new model for testing, training and demonstrations. Specifically, we wanted something that would allow us to test the full capability…
Which Should I Use? Real & imaginary? Or magnitude & phase?
In one of our recent articles a question was asked regarding the practical use of real & imaginary type plots compared with modulus & phase type plots. In general, noise…
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.
Vibration Monitoring Phase Measurement And The Tacho Signal
Any 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 phase for vibration monitoring. Most vibrations on a rotating machine are related to the rotational speed so it is clearly important to have a measure of the speed, either directly or as a once per revolution tacho pulse. A question sometimes arises as to whether a once per revolution tacho reference signal is needed to measure phase. Is it possible to get phase if we only have a speed signal? This note gives some insight into those questions.
Actually the question that should be asked is – “Can we measure a meaningful phase, for use in vibration monitoring, if we only have a speed signal as well as the vibration signals?”
