Comments on: TORSIONAL VIBRATION, TACHO PULSES AND ALIASING http://blog.prosig.com/2006/01/12/torsional-vibration-tacho-pulses-and-aliasing/ Notes, tutorials, news and articles on digital signal capture, processing, techniques and applications Thu, 28 Aug 2008 16:15:46 +0000 http://wordpress.org/?v=2.5 By: Colin http://blog.prosig.com/2006/01/12/torsional-vibration-tacho-pulses-and-aliasing/#comment-55 Colin Mon, 10 Dec 2007 14:49:45 +0000 http://blog.prosig.com/2006/01/12/torsional-vibration-tacho-pulses-and-aliasing/#comment-55 Hi Afraid you are correct! You really need more than six pulses per rev to find torsional vibration with any measure of confidence. The torsional vibration is basically assessed by using the timing differences between the expected non vibrating time of arrival and the actual time of arrival. If your torsional vibration frequency is low with respect to the shaft rotational frequency then you can "cheat" by saying you have say 12 pulses per revolution. This is treating two revolutions as if they were one revolution. There will be a factor of two in frequency and provided each revolution is essentially the same you will get some idea of what's going on. BUT do not place huge confidence on the result! It could however give you sufficient evidence to see if you possibly have a torsional vibration Hi
Afraid you are correct! You really need more than six pulses per rev to find torsional vibration with any measure of confidence. The torsional vibration is basically assessed by using the timing differences between the expected non vibrating time of arrival and the actual time of arrival. If your torsional vibration frequency is low with respect to the shaft rotational frequency then you can “cheat” by saying you have say 12 pulses per revolution. This is treating two revolutions as if they were one revolution. There will be a factor of two in frequency and provided each revolution is essentially the same you will get some idea of what’s going on. BUT do not place huge confidence on the result! It could however give you sufficient evidence to see if you possibly have a torsional vibration

]]> By: Antonio Aufiero http://blog.prosig.com/2006/01/12/torsional-vibration-tacho-pulses-and-aliasing/#comment-42 Antonio Aufiero Thu, 06 Dec 2007 09:30:11 +0000 http://blog.prosig.com/2006/01/12/torsional-vibration-tacho-pulses-and-aliasing/#comment-42 Is it possible use a tacho with 6 pulses for rpm in order to analyse torsional vibration ? I don't think 6 theeth are enough ! bye , many thanks in advance Antonio Aufiero Is it possible use a tacho with 6 pulses for rpm in order to analyse torsional vibration ?

I don’t think 6 theeth are enough !

bye , many thanks in advance
Antonio Aufiero

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