Perform Frequency or Order Analysis in DIAdem Based on a Tachometer Signal?

Updated Jul 11, 2018

Reported In

Software

  • DIAdem

Issue Details

I'm trying to perform some frequency and order analysis based on a tachometer (pulse) signal, but when I use Pulse Detection analysis the new signal length becomes incompatible with the other signals, then it is not possible to perform those analysis.
  • How can I prepare/resample the signal to those analysis? 
  • How do I convert signals with different x-values (downsampled, oversampled or non-linear) to a common x-range?

Solution

In many analysis on DIAdem all channels to be analyzed inputs must be of the the same length, so before them we need to prepare the signal. In the case of tachometer signal, when you convert the pulse train into RPM signal the x-axis values becomes different from the original x-axis signal.
In order to solve that, follow the steps below to resample and linearize the signal to the next desired analysis.
  1. Convert the tachometer signal (pulse train) into a RPM signal using the Pulse Detection analysis (Figures below);
  • Configure the Time channel and Tachometer channels.
  1. The result will be two channels, one for the RPM values (PulseDetectedRevolution) and the other an appropriate time channel (PulseDetectedRevolutionTime), since the the resulting x-axis will non-linear.
  1. Now, convert the RPM x-values (PulseDetectedRevolution) into a common x-range using Linear Mapping analysis.
  • Configure the Channels to be mapped. X-Channel  should be the x-axis of the RPM signal (PulseDetectedRevolutionTime), Y-Channel the RPM signal (PulseDetectedRevolution) and Interpolation channel the data channel of the x-range to which DIAdem calculates the values, in this example the Sound Pressure x-axis channel.
  1. If the channel is a waveform, like in the example, you will need to create a x-axis from it. For that, use Numeric Channel <-> Waveform Channels analysis with the following configuration.



 
  • After that, you can return to the step before to map the signal linearly.
  • Finally, you have LinearMapped signal as a ready signal to be used on a frequency or order analysis.

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