On the attached single parameter trend plot with the associated PeakVue spectrum and twf, notice that the information in the trend display and the twf do not match.

My collection parameters are 120 cpm low freq limit, 0-120000 cpm, 1600 lor, 1 average, 2000 hz hp filter, no special twf.

Looking in the Example.rbm database, I see that a peakvue point is set up there to collect a special twf and that the info in the trend plot matches that in the twf.

These collection parameters are 2 hz low freq limit, 0-2000 hz, 1600 lor, 8 averages (this is from before the 1 average recommendation), 2000 hz hp filter, collect special twf to 80 orders/1024 pts.

What am I missing?

p-ptrend.doc (77 Kb, 40 downloads)

I'm not sure what you're missing. My numbers match up and I don't have any of my peakvues set up to take special twf. Also, my waveform parameter is set up like yours, MP Wave, and not like the Example.rbm, P-P Wave.

OK, I lied. I wrote all that and kept looking around and found the same thing on a few points. In the FFT, hit F8 (Analyze Options), and choose 'Stored Parameters' and that's what is actually saved during the route and what is put into the trend. Under Analyze Options, choose 'Calculate Parameters' and it will re-analyze the band parameters. Now on a regular point, re-analyzing is useful if you change the running speed or something, but I don't see why the waveform parameters would change.

Now I'm missing something, too.

Hi Danny,
I'm attaching one of our Peakvue signature here. We are using P-P Waveform parameter and the readings in the trend and twf are matching. No special twf collected. In your case, you are using max twf peak for trending where as the waveform is still showing P-P reading. So it will never match

Peakvue.MDI (26 Kb, 25 downloads)

Patrick,

I just altered the ap and al sets in this route. The data collected was done with different parameters and limits, so I hope that the next time I collect data on this route, I won't have this problem.

Jenish,

Where it says "max twf peak" is just the heading for the graph. I could have called it "Danny's graph" or anything else. As long as I set the type of parameter to p-p wave that is what it should plot.

The discussion about how we look at data made me decide to try to fine tune the alarm limits and I figured that this route was a good one to start on since it is mostly fans and there are only 3 different configurations. I'm going to hope that the next set of data will work out right and I'll let you know how it works out.

To all,

Does anyone know why CSI recommends ( at least the Wizard does it automatically ) collection of a special TWF?

The above means that spectrum is constructed based on the TWF collected using spectrum AP set but the TWF is not plotted. Instead, the special TWF actually gets displayed.

This message has been edited. Last edited by: David_G,

I think this was introduced years ago (10 or more) when someone who worked for CSI convinced them to add this feature because it is a benefit from time to time to gather a waveform that has a different time length (usually "longer") than the one actually associated with the stored spectrum. Why the Wizard does it automatically, if it does, I don't know. I guess someone who built the Wizard liked the option.

Personally I like this option. All my normal routes, well most all, have a special waveform taken out to at least the equivalent of a 3000 Hz Fmax, That is if the spectrum stored is less than 3K Hz.

Just my opinion and I could be totally wrong.

I always understood that it was because when you select (as recommended) digital integration with units of velocity it will store the twf in velocity also. They created the collect special twf feature so that you could see a twf in acceleration and use digital integration.

That still doesn't explain why my trend graph shows one thing and the twf shoes another.:-(

Not sure why the mismatch in numbers, a call to customer support would probably solve it.

The best integration mode is analog for dynamic range and amplitude accuracy, but then a special TW needs to be collected in G's accel, because analog leaves the TW in velocity units.

quote:

I always understood that it was because when you select (as recommended) digital integration with units of velocity it will store the twf in velocity also. They created the collect special twf feature so that you could see a twf in acceleration and use digital integration.

Could be Danny. I am sort of quoting the guy who claimed that he was the one who convinced CSI to add this STWF option to the CSI program. Wish I could remember his name. it just so happens that I am going to a users "get to gether" this Thursday , people from different plants around MS and AL meet to swap stories, and this guy was at one of these "get to gethers" years ago when he said this about the STWF. If he is there I will ask about it.


On the other note:
I have looked at some of my old PV data and the Max Peak parameter I have setup in acceleration trend matches all my waveform amplitudes with no STWF collected, at least the couple of dozen I looked at. Hmmmmm

quote:

Originally posted by Danny Harvey:
Jenish,

Where it says "max twf peak" is just the heading for the graph. I could have called it "Danny's graph" or anything else. As long as I set the type of parameter to p-p wave that is what it should plot.

You are right Danny.. Actually what i thought was in your parameter settings you select the "Max Pk Waveform-MP Wave". If your unit type is "acceleration", your Parameter type is "P-P Wave" and your frequencies are set as zeroes in your parameter set for peakvue, it is ok.

In the documents from CSI regarding peakvue, it is given as follows:

"It is important that "P-P Wave" is chosen for the "Type of Parameter" and that no frequencies are assigned to the "Lower and Upper Frequency" columns. This will assure the user that only the True Pk-Pk value is captured from the PeakVue waveform since the Trend Parameter section clearly states "The primary PeakVue parameter which should be used for trending PeakVue measurements is the parameter referred to as "Pk-Pk Waveform"

quote:

Originally posted by David_G:
To all,

Does anyone know why CSI recommends ( at least the Wizard does it automatically ) collection of a special TWF?

David,

CSI's explanation for taking SWF is:
"It is sometimes necessary to obtain a special PeakVue time waveform in order to display the proper number of revs using the recommmended setup information, along with the helpful equation relating the number of Revs to the #FFT Lines and Fmax(in orders)." Anyway we are not taking a SWF for peakvue in our setup.

quote:

Originally posted by Ralph Stewart:
... to gather a waveform that has a different time length ... than the one actually associated with the stored spectrum.
Personally I like this option. All my normal routes, well most all, have a special waveform taken out to at least the equivalent of a 3000 Hz Fmax, That is if the spectrum stored is less than 3K Hz.

Back to special TWF...

First, units in STWF could be selected as desired, so integration apparently is not an issue with STWF.

Secondly, (I am in agreement with Ralph) STWF allows collection of a TWF with parameters other then that defined by the spectrum. If so, how can we turn this to our advantage? Say, a spectrum is set with Fmax=2000hz, but STWF with Fmax=3000hz (LOR same).
In this case time length of the data block will be shorter, better resolution. Are there other benefits? Will we see impacts better? Will amplitudes be higher? Of course, we can also set LOR higher to enhance TWF resolution (data block time will be shorter).

A lot of combinations, depending on needs, but in a survey program what is going to be practical, if any?

This message has been edited. Last edited by: David_G,

Well I am deleting all my stupid remarks on the waveform and the "0" thing doing this and doing that. I have found some problems and changes that have been made into the waveform display that seems to have some conflicting issues from some other things I see. Glad I quit complaining about bugs. And just "roll with the flow".