NVH sensor which use?

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NVH sensor which use?

Postby LucaB » Wed Jul 16, 2014 12:12 pm

Hello everyone, I have seen this sensor, my question is:
What diagnose exactly with this sensor?
What help can I give?
I see frequency of a noise, but then how do I know if the injectors, valves, wheel bearings, gearbox, etc..
I hope you understand my English
Greetings to all.
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Re: NVH sensor which use?

Postby Steve Smith » Wed Jul 16, 2014 8:23 pm

Hello Luca and thank you for your post. Your English is fine and far better than my Italian.

This is a very loaded question as NVH (Noise Vibration Harshness) is a specialist area of engineering that requires some homework and study to understand the foundation on which the tool operates.

Having said that, it is no more difficult than the oscilloscope which I am sure when you first started using raised more questions than answers.

The NVH tool and software will enable you view the strength or amplitude of a vibration, relative to the speed or frequency at which a component rotates.

Think about the oscilloscope how we look at the amplitude of a voltage (y axis) relative to time (x axis)
The NVH software changes the time base to represent “frequency” along the x axis and changes the amplitude to show the strength of a vibration (y axis).

This is called “Spectrum mode” and you can see an example of a spectrum view from your PicoScope 6 automotive software.

Please do not despair at this point as all will become clear. It is vitally important to grasp the information above because with this foundation in place you can then interpret the results obtained.

So how does the NVH tool help me find the location of vibration and noise? E.g. wheel bearings, gearboxes, injectors etc.

A vital piece of information here, Sound and Vibration are one and the same!
In other words, sound is simply a vibration you can hear, vibration is a sound you can feel.

The NVH kit is equipped with a microphone and an accelerometer for sound and vibration measurement. By attaching either device, the amplitude (strength) of the sound or vibration is displayed in the NVH software just as voltage is displayed on your scope.

Now, using both the engine and road speed signal from your on-board diagnostic connector, the NVH software can display the frequency (speed) at which your vibration is relevant.

Think of it this way, if we know the engine and road speed and also enter into the software all the gear ratios and tyre sizes of the vehicle under test, the software is able to provide the complete spectrum to display the rotational speed (frequency) of all components on the vehicle.

We can now see all the vibrations levels (amplitudes) plotted against their rotational speeds (frequency) this enables the user to identify either the area of concern or the offending component itself.

Often vibration is perceived differently by different people and so the NVH tool can also give the user the ability to measure vibration and sound levels for “back to back” analysis, proving to customers that a problem is actually characteristic and not a “problem” at all!

Here is an example.

A 4 cylinder engine rotating at a speed of 3000 rpm rotates at a frequency of 50 Hz (50 cycles per second)

Divide 3000 RPM (Cycles per minute) by 60 to achieve RPS (Revs per second or better known as Cycles per second, Hz)

Now any vibration levels that show a high amplitude around 50 Hz have to be engine related.

There is however far more to it than all the above as we have a phenomena called “Vibration order” This must be studied but will again assist with analysis.

The NVH help files will guide you through the set up and analysis process and also contain great theory to help with mastering what is an art of its own.

I have attached an NVH file from a test vehicle with a vibration evident at 70 MPH called T1. Please load this into the Beta NVH software and try to detect the likely cause of the vibration.

GOLF 70 MPH VIBES WITH ACCEL AND OVERRUN.pddata
(3.17 MiB) Downloaded 499 times


I hope this helps, take care……Steve
Last edited by Steve Smith on Wed Jul 16, 2014 9:16 pm, edited 1 time in total.
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Re: NVH sensor which use?

Postby Steve Smith » Wed Jul 16, 2014 8:24 pm

See attachment in previous post.
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Re: NVH sensor which use?

Postby swissmister » Sat Aug 30, 2014 11:40 am

Hello Steve
I was reading up on your nvh kit and found your response in this forum. From what I understand along with the nvh kit an elm obd adapter would be required to get the engine rpm and vehicle speed. Is there a preferred part/ obd software pico recommends?
I also wanted to look at the .pdddata file you attached, but I was not able to find the nvh beta software to download.
is this available for download/ review? Could you direct me to it?
Thanks
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Re: NVH sensor which use?

Postby tode » Sat Aug 30, 2014 4:56 pm

I was observing this tool, it seems very interesting, I noticed that only has one input, which connect either the accelerometer or microphone, in that occasion you should use one or the other? Would not it be useful to be able to connect both sensors?
Thanks
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Re: NVH sensor which use?

Postby macfarad » Sun Aug 31, 2014 8:21 am

I was also very curious on how the NVH kit would work. I always wondered if there was an affordable, more 'scientific', approach for noise and vibration complaints.

In Europe, I think NVH equipment is rather rare in the automotive-aftermarket. But when I search Google, it appears that in the US NVH-testing is more common, and that Pico even delivers the NVH kit to the GM Dealer Network:
http://sandyblogs.com/techlink/?p=2879

That said, I have tried the open the file Steven posted, using the beta-version of Pico Diagnostics, but I get an error message: "Unable to load file". Am I the only one with this error?

It also might be a good idea to update the Pico Automotive channel with a video on NVH testing in a real life example.

A bigger problem is that my PicoScope is already a few years old, I still use the 3423 model. On the website it is stated that a 4000 series is required to use the NVH kit.
That would make the NVH kit quite an investment for me.

Perhaps Pico can do a special upgrade offer for 3000-series users who purchase the NVH kit together with a 4423? :wink:

Kind regards.
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Re: NVH sensor which use?

Postby asimoes » Mon Sep 01, 2014 11:33 am

Hello

I am Alex from Brazil , i had been used a lot PICO NVH here and I would like say it`s a good equipment to do this type of diagnoses. In the past we used here another device, but I am glad to say this one is better.

I wold like to know if PICO group are planing make some training about this subject?

Thank you
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Re: NVH sensor which use?

Postby Steve Smith » Mon Sep 01, 2014 8:23 pm

Hello Swissmister, thank you for the post and sorry for the late reply.
The attached NVH file can be opened by downloading and installing the current BETA software at [https://www.picoauto.com/software-picoscope-automotive.html][/url]

Click on the large blue download button and select BETA not stable version.

The current BETA is version 6.10.2

Regarding the ELM lead (J2534 standard interface), we have used this lead with great success to access engine and road speed data from the OBD connector on various models. I have also used the Mongoose lead to great effect with Japanese and German vehicles.

There are numerous devices on the market at present that support the J2534 standard interface and research is still ongoing as to which lead to recommend as the choice is endless.

I hope this helps, take care......Steve

You can also access the engine speed via a "Tach" signal present on pin 9 of certain specification vehicles, so removing the need for any generic OBD communication tool.

Another option at present is to enter the engine speed manually if you can identify the point at which your component vibrates etc.
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Re: NVH sensor which use?

Postby Steve Smith » Mon Sep 01, 2014 8:43 pm

Hello Tode and thank you for the post and suggestion.

We have discussed such an improvement to the NVH kit and I can see the benefits of 2 x inputs into the NVH software.

A typical scenario would be attaching the accelerometer to the chassis to monitor engine vibration, whilst a microphone inside the cabin could monitor the noise level. If both these coincide at the same frequency we would know the vibration was also the cause of the cabin noise.

At present there are no plans to implement such a modification but the idea is certainly in the "ideas funnel" and will be addressed in the future.

I firmly believe the NVH kit at present is a god send when looking at such issues using either the microphone or the accelerometer.

I hope this helps and please all continue to think out loud and post suggestions/improvements about any of our products.

Take care.......Steve
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Re: NVH sensor which use?

Postby Steve Smith » Mon Sep 01, 2014 9:26 pm

Hello Macfarad and thank you for your post.

I have downloaded and ran the attached file using the current Beta software version 6.10.2 containing the Pico Diagnostics software version 1.7.0 build 5
All ran fine with no issues.

Could you confirm you have these versions installed?

If so could you uninstall and install the beta version again and feedback if you still have further issues?

Moving onto an NVH tutorial/Video/Case study, I whole heartedly agree and rest assured these are being discussed in order to support the NVH kit and the technicians using them.

Regarding NVH only operating only with the 4000 series scope, I have to admit I am not 100% sure why it would not operate with the 3000 series!

I am out of the office tomorrow but rest assured I will check this and feedback to you ASAP.

Thanks again for the feedback, take care……Steve
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