Waveform display issues

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Liteace
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Waveform display issues

Post by Liteace » Fri Mar 23, 2012 3:16 pm

Hi All used my scope today for the 1st time wanted to check MAP and o2 sensor but having a small problem with display, as you can see I cant get a nice neat fine line, blue trace MAP, red trace o2, what am I doing wrong ?

picowave.png
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GRUSS
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Re: Waveform display issues

Post by GRUSS » Fri Mar 23, 2012 4:37 pm

Looks as though your capturing quite a bit of interference, try hanging the leads away from the ignition. Turn your sample rate down to loose some of the hairy spider,Slowly adjust the resolution Upwards from 12bit to see if that clears it up. Also try adding a low pass filter to the capture after you have stopped the recording. I'd also lower thetime base to say 10 seconds as well..
HTH

Alan
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Re: Waveform display issues

Post by Alan » Fri Mar 23, 2012 5:42 pm

Great advice from Gruss above. Moving the leads away from sources of interference may help a bit but the noise is probably present in the wiring loom of the vehicle due to wires being close together - this is normal. The low pass filter option should remove the noise (filters inside the ECU do the same thing).

I would also up the 1V range used for the 02 up from 1V to 2V as with the noise on top of the near 1V signal its going slightly out of range.

If you are having problems getting the filtering sorted then upload the waveform and one of us will tweak the file for you.

Dave Hill
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Re: Waveform display issues

Post by Dave Hill » Fri Mar 23, 2012 10:50 pm

I tend not to be overly concerned with noisy captures. In the early days of scoping I became a little obsessed with trying to get a super clean signal, like those seen in the "Automotive Pre-set" examples. Real life capturing is seldom so tidy though & now Pico have given us the ability to apply filters to files that we have previously saved, there seems less of a reason to even think about filtering a live capture. In fact you will often limit yourself in doing so.

Just my thoughts.

:D

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Robski
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Re: Waveform display issues

Post by Robski » Sat Mar 24, 2012 8:24 am

Agreed...................take the capture............clean up after...............don't worry when capturing live.

Liteace
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Re: Waveform display issues

Post by Liteace » Sat Mar 24, 2012 10:04 am

Thanks guys the filter has done the job
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Liteace
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Re: Waveform display issues

Post by Liteace » Sun Mar 25, 2012 11:25 pm

So would the filter work on say this waveform:

http://www.picoauto.com/support/post25756.html#p25754

of MAF that Gruss posted,

Sorry for all the question, Im have been using various scopes over the years and never seen a waveform like these, they have all been just a line
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Robski
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Re: Waveform display issues

Post by Robski » Mon Mar 26, 2012 6:36 pm

Yes a filter will work,you just have to be careful you don't filter too much.

Liteace
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Re: Waveform display issues

Post by Liteace » Mon Mar 26, 2012 6:37 pm

Thanks for the help guy's, all the scopes Ive had over the years have never had a filter, they've just displayed a line so that through me a bit

Thanks
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Robski
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Re: Waveform display issues

Post by Robski » Mon Mar 26, 2012 6:39 pm

It also depends how much sample rate you have set, the higher the rate the more dots drawn.

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