4423 scope and a/c power to my laptop?

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4423 scope and a/c power to my laptop?

Postby hexibot43 » Tue Nov 05, 2013 7:55 pm

I just went back and checked the manual before asking this question. Can I have my laptop hooked up to the mains while I am using it as a scope with the 4423 scope? I was just looking at a car and getting some rather strange readings. I unplugged the laptop from the mains and the odd pattern went away. How did it get in the signal path? My AC lines were no where near my probe lines. Do most people disconnect from the mains when using the scope?

Thanks,

Marcello
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Re: 4423 scope and a/c power to my laptop?

Postby Robski » Tue Nov 05, 2013 9:30 pm

Do most people disconnect from the mains when using the scope?

I do on one laptop & not another :?
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Re: 4423 scope and a/c power to my laptop?

Postby Valhalla » Wed Nov 06, 2013 12:18 am

I have to disconnect from mains on both my laptops. Unfortunately, the battery has gone on the second one, so that is a problem at the moment. Main laptop is a Dell E6520, second is a Dell M70.

I am going to do an experiment to see if a PC workstation can be put together that does not suffer this problem, i.e a decent filter on the power supply. My biggest problem is not the power supply, but the building that I work within. I get a bad interference off the mains ring circuits, so have to isolate the incomer for some jobs. So for really sensitive work, I have to use the laptop on battery, outside of the building.
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Re: 4423 scope and a/c power to my laptop?

Postby Fat Freddy » Wed Nov 06, 2013 10:04 am

Do most people disconnect from the mains when using the scope?


I don't. But I have had mains hum stall an engine when connected to a crank sensor and being sloppy with the gnd connection.

FF
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Re: 4423 scope and a/c power to my laptop?

Postby hexibot43 » Thu Nov 07, 2013 6:38 pm

Thanks everyone for the replies. I'm now feeling much better. I'm not alone. I'll be using my older T43 from now on which I have an adapter to hook straight to a car battery. I'll put a battery on my cart, and hopefully be seeing a nice clean signal from now on.
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Re: 4423 scope and a/c power to my laptop?

Postby Steve Smith » Thu May 08, 2014 11:48 am

Hi and thanks for the posts on this subject. I can see you resolved the issue using an alternative power supply but could you post an example of the noise/strange reading you experienced when measuring with your lap top connected to the mains? The psdata file would be ideal as it would be great to see the effects on your signal before and after mains disconnection.
Can you confirm if you were using the Blue Pico USB lead with the above issue, as this removes one possible from the equation?
The grounding of certain laptop power supplies is questionable at best and the results can affect the integrity of your measurement signal.
Once again any feedback is appreciated although my reply is late to say the least.

Take care......Steve
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Re: 4423 scope and a/c power to my laptop?

Postby Peter K. » Sat Aug 02, 2014 11:00 pm

Hi,

If I can use this topic, I like to share my experience.
I was testing my friend Opel Meriva A 1.7CDti, which has a starting problems. After performing battery test, it turned out, that starter was obviously bad, just looking test resaults. Even car battery has a bad cell.

After replacing starter, with exchanged unit, and new Varta blue dinamic battery fited, I performed battery test again! I always do this test after replacing components, just to check charghing system. It turned out, that alternator ripple is too big (arround 1V). But why is this happend after replacing starter, and a fresh new battery?

After spending 3 hours researching, and testing, its turned out, that the problem is my laptop IBM T400 connected to the mains. Even with laptop plugged in TRUST 12V car chargher seems to have same issue.

Below is psdata file, when laptop is unplugged to main (laptop have bad battery) and other one is when I plugged on main.

Now I`m buying new battery for my laptop.

Best regards,

Peter
Attachments
Unpluged.psdata
(4.01 MiB) Downloaded 205 times
Plugged 220V.psdata
(7.32 MiB) Downloaded 207 times
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Re: 4423 scope and a/c power to my laptop?

Postby Steve Smith » Mon Aug 04, 2014 8:16 am

Hi Peter and thank you for the feedback and waveforms too.

You have hit the nail on the head regarding "Noise" and just how visible some devices can be when connected to the mains.

I have seen this on numerous occasions which of course is more visible when looking at low frequency, low voltage signals.

This is something we must be aware of when using chargers, transformers, and inverters of differing quality, or even older premises with poor grounding. (I have worked at premises with water leaking through the roof, down the walls via electrical distribution boards on route to the workshop floor!) All good experience!!

What proved a valuable feature with PicoScope in your attachment "Plugged 220 V" was the Low pass filter, but be aware of over filtering.

Take care......Steve
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