New User - NVH Diagnostics Kit

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New User - NVH Diagnostics Kit

Postby demodan » Wed May 18, 2016 3:33 pm

Hi,

I have recently purchased a 4 channel Pico scope and a 3 axis NVH Diagnostics Kit.

The system was easy to set up using a Mongoose J2534 lead recommended by Pico and the Wizards in the Pico Diagnostics software.

In advance of using the kit in anger next month I've now carried out some initial trials with both accelerometer and microphone.

I've run into the following problems which I can't fix:

1. Recording only makes the last 50 seconds of data available. Most of the tests I have been doing are 4 to 6 minutes long so this means I have no access to a large amount of the data.
2. Audio seems to be out of sync with the graphs (when I use microphone)
3. Graphs don't seem to be in sync with each other (see attachment)
4. SPL signal is off the scale on lower graph and it doesn't seem to be possible to adjust the scale

I've looked for ways of adjusting parameters and can't find any way of fixing this.

Please help.
Attachments
Capture.PNG
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Re: New User - NVH Diagnostics Kit

Postby demodan » Fri May 20, 2016 10:02 am

This second screen grab shows how the SPL is going out of range on the lower graph and needs re-scaling.
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Capture - airborne.PNG
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Re: New User - NVH Diagnostics Kit

Postby demodan » Fri May 20, 2016 10:02 am

Please also advise - is the sort of post I should be putting on the forum or should I call the helpdesk?
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Re: New User - NVH Diagnostics Kit

Postby PhilS » Sat May 21, 2016 3:01 pm

Hi demodan

welcome to the forum, PicoScope and our NVH system.

One of our technical experts, Steve, will be in touch - I wanted to offer some feedback in the meantime.

Firstly regarding the 50 second limit. This is a default setting to keep the size of the captured data file to a reasonable size. You can increase this setting to 500 seconds using the Signal Options line as seen below:

NVH 50 Seconds.gif


You can also use the pause/resume functions to capture several 'incidents' within a single run. The signal markers are also very helpful when making an extended run to flag the problems that you heard/felt.

Regarding the SPL scaling - I have captures with much higher range than that (they are auto scaling), so we would like to look at the data files. I couldn't really make out the sync problems you mentioned and would like to examine the data for those inside the software.

What would really help for any problems/questions is to post .pddata files (and .psdata for PicoScope), as that allows us to actually load them up and investigate. Although screenshots are helpful we cannot use them with the software, and the ability to zoom in and see the detail is a big help for those of us with small screens.

As a general rule, the forum is great for sharing and asking advice from other regarding vehicle and diagnostic questions, tips etc. The Waveform library is another great way of both sharing and accessing the captures that others have made for different systems and components across different vehicles.

In the case of problems with the hardware or software, or help/advice on how to use or configure the system, then it is best to email support@picotech.com or call our offices in the UK or USA (just ask for technical support). We have a tracked ticket system for all queries into the helpline, whereas the forum is not structured and controls. With so many posts and topics it is a lot harder for us to always spot a problem raised in that way.

I also noticed that you are using the 3D frequency charts in NVH. That's great if you are used to those, and some of our experts can easily spot problems using those charts. Personally, and I think also for many new users, the simpler charts are a lot easier for me to use. So a bargraph or frequency chart in the first instance, and maybe the road speed or RPM order for road speed or engine speed related problems respectively. I think many users will also find the new time domain view to be really helpful for many applications, particularly harshness and suspension related issues.

Please do contact us at any time, but please also send through the .pddata files for us to look at.
It is also really helpful to let us know which version of software you are using - sometimes we are aware of problems that have been (or will be) fixed in a later release.

Best regards,
Phil
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Re: New User - NVH Diagnostics Kit

Postby Steve Smith » Sat May 21, 2016 3:53 pm

Hello and thank you for the post.

I have just seen that Phil has replied and some of the info mentioned is alos contained here but I will post either way as I have already typed this up.

You are most welcome to post anything here on the forum as this will allow everyone to see and share in the discussion.
You also have the support@picotech.com support line for any concerns you have with the Pico products.

Your feedback, questions and queries are what drives the Pico products along and ultimately result in improvements with added features.

1. Only 50 seconds of data available? This is the default recording time of the NVH software but can be extended to a maximum of 500 seconds:
Remember, whilst recording, you can press the space bar to pause recording if the vibration has cleared (or you need to stop the vehicle) and restart when relevant

INCREASE NVH SIGNAL HISTORY.jpg
Signal history


2. Audio seems out of sync with the graphs? Would it be possible to post your Pddata file here for review?
I can see that your second attachment displays the 3D graph with the microphone and you have highlighted data in your signal history between 240 and 242 seconds.
This selected data is then displayed in the 3D graph where it appears your highest audio level is indicated as a Tyre or Engine vibration order (Low frequency).
This level of vibration/sound would be better suited to the accelerometer, with a spectrum of 0-200 Hz.
This is not to say you cannot use the microphone because vibration and sound are one and the same. (Humans however feel vibrations from 0-20 Hz, not hear)
I would like to see the PDdata file where we could then reduce the size of your spectrum to enable better visibility /resolution of your peak audio amplitudes. I can then repost a screen shot that will help clarify the suggestion above. Please forgive me if I have misunderstood your question and this is not your concern, if you could feedback back on this issue that would be great.

3. Graphs don’t seem to be in sync with one another? Looking at the graphs you have posted, one uses an accelerometer (0-200 Hz) and the other uses a microphone, (0-1700 Hz) both of which contain different data in the signal history, hence the data in the 3D display. Could you assist further here with your concern as these are different displays with different inputs and could not be in sync? (I hope I have understood your question)

4. SPL is off the scale? In your second attachment your signal history is indeed over scale as the mic would appear to be located at the source of the noise, or in a noisy environment. To rescale, select “Engine Bay” at your set up screen as this will adjust your scale to allow for noise levels expected in the engine bay. The over range here may well effect the amplitudes we see displayed in the 3D frequency graph.

ENGINE BAY SET UP-MIC SETTING.jpg


Could I ask if you were chasing a resonance type vibration/noise? The 3D display works very well in this scenario given resonance is present for a short time frame and using the 3D frequency display allows you to graph the build and decay of resonance as it appears.
If not, I would suggest the frequency display or the bar graph display to remove some of the additional information on display that is not relevant. (Easier on the eye)

I hope this information is of some help and please feedback when you can

Take care.......Steve
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Re: New User - NVH Diagnostics Kit

Postby demodan » Tue May 24, 2016 4:37 pm

Hi Phil & Steve,

I've read through all of Phil's post and will look at Steve's when I get in tomorrow but I gather that you both want to look at the pddata file so I have attached this.

My concern about the unsynched graphs can be seen most clearly in the vibration data screen shot I took. This is highlighting the time period 8-10seconds with a peak in both engine rpm and speed at 10 seconds. The order curve however starts to decay from around 9 seconds (hence the curved shape) indicating that either the order curve is around 1 second out of phase (ahead) with the frequency map or the entire frequency/order map is 1 second out of phase with the rpm/speed/g graph.
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Re: New User - NVH Diagnostics Kit

Postby Steve Smith » Wed May 25, 2016 10:30 pm

Hi Demodan thanks for the feedback. I have the file and will look into this ASAP.

Forgive the delayed response

Take care.......Steve
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Re: New User - NVH Diagnostics Kit

Postby demodan » Thu May 26, 2016 10:15 am

Hi Phil & Steve,

Between you my questions 1 & 4 are answered.

Hopefully I've explained what I mean by question 3.

For question 2 - audio out of sync with graphs, you need to play back the pddata file I uploaded with PC sound on. If you start playback at any point in the recording you will hear approx. 1 second of background noise, followed by a buzz (which could be all frequencies played back at once) - this happens wherever playback is started so is definitely out of sync with the data recording.

Thanks

Dan
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Re: New User - NVH Diagnostics Kit

Postby Steve Smith » Thu May 26, 2016 11:02 am

Hello Dan, thank you for the feedback.

I have just played the audio file and it sounds like over modulation followed by "feedback" based on the microphone gain and input noise level.

The initial 3 seconds of the recording is audible but then falls silent after a period of "feedback".

Would it be possible to carry out a similar test with the mic set to engine bay as per my second screen shot?

I will check with the development team to see if this condition is expected behavior when the input signal is over range or indeed if we have a software bug.

Could you confirm the mic is working correctly in a less noisy environment? (Take a recording of your voice)
This will eliminate any hardware issues before we proceed.

Moving onto the 3D frequency display screen shot, could you post the PD data file for this capture?

I have included the same screen shot below with the 9 second point marked for viewing the order curves.

SCREEN SHOT.jpg


Could you indicate the phase error in relation to the curve and the signal history? (Rpm Speed graph)

I would like to add more signal history time to the 3D display to view the effects upon the order curves

Thank you again for your feedback

Take care........Steve
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Re: New User - NVH Diagnostics Kit

Postby demodan » Mon Jun 06, 2016 10:58 am

Hi,

I've been away on factory shutdown for a week so will try to grab the information you need when I can.

Dan
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