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LMS Test.Lab: What is 'raw:Tacho'?

In my LMS Test.Lab throughput files, I always get a channel that starts with 'raw:' and then has the name of my tachometer channel?

 

What is it?  Do I need it?  Picture below

raw.png

 

 

 

 

3 REPLIES
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Accepted by topic author Eng1
‎06-05-2017 08:04 AM

Re: LMS Test.Lab: What is 'raw:Tacho'?

Hello,

 

this is (like the name says) your raw tacho signal. This signal contains your tacho slopes/pulses in a cumulative format.

Maybe you know a raw tacho signal where you can see your rectangular pulstrain from your tacho sensor (like in LMS Test.Lab in Tracking Setup)? These pulses are counted and a rotational speed is generated (usulay in RPM).

This is the same information which is included in the raw tacho signal in LMS Test.Lab but in a different way. In the Test.Lab data format the occurance of a tacho pulse is alway measured from the start of a measurement. Means if you export a tacho signal and open it with e.g. Excel you have a table withe one column where the pulses are consecutivly numbered in ascending order und a second colum with the corresponding point of time.

In your graph you can see for example that your 100th measured tacho pulse "happend" at 9.5 seconds after the start.

Based on the contained information of the raw tacho many processings in LMS Test.Lab are done like e.g. if you want to analyze torsional vibrations based on your tacho signal etc.

 

Keep it! You dont know if you will need it someday :-)

 

Re: LMS Test.Lab: What is 'raw:Tacho'?

Hello,

 

Yes, I agree with everything that alangm stated.  I refer to the raw tacho trace as the tacho "moments" or the point in time of each pulse crossing at the trigger level you set.  It is required and used in Order Tracking and Angle Domain analysis to best analyze your tacho signals.

 

Kevin

Re: LMS Test.Lab: What is 'raw:Tacho'?

Thanks for the information.  In fact, this ended up to be very helpful.  One of my work colleagues asked for the time stamps of the tachometer crossing points, and I just right clicked and exported the raw tacho trace to Excel for him.  He wanted "the most compact and efficient" data points that could be used to reconstruct the rpm.