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Re: A useful addition to your toolkit
wrote:

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It's not hard to figure where current is going: just measure voltage
drops. What's sometimes difficult is quantifying it.

Just now we're laying out a 10-layer board with two ground planes and
three power planes. There are 22 power supplies. Most of the power
distribution will be interestingly-shaped interleaved pours, not
traces, on various layers.  

That magnetic gadget would be hopelessly confused. Multiple currents
and various return paths would make it useless.

My favorite tool for tracing unusual current flows is my Flir E45
thermal imager. It cost $12,000.

We just demoed a cool new thermal imager, mounted on a nice little
stand, with its own display and also USB interfaced for pics or
movies. They're going to let us keep it.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: A useful addition to your toolkit
John Larkin wrote...
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 Names, please.  And results, later.


--  
 Thanks,
    - Win

Re: A useful addition to your toolkit

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We don't believe it until there are pictures.



Re: A useful addition to your toolkit
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I'm not sure I can name names yet. It's still in development.

We've become sort of a beta tester for these people. They send us
units and get our feedback, and we can keep them. Or maybe they just
like coming to San Francisco.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: A useful addition to your toolkit
On Mon, 06 Mar 2017 20:56:00 -0800, John Larkin wrote:

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Unlikely. ;->


Re: A useful addition to your toolkit
On Tuesday, March 7, 2017 at 1:21:14 PM UTC-5, Cursitor Doom wrote:
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Maybe they could not find any flowers :


https://www.youtube.com/watch?v=bch1_Ep5M1s


Sorry I did not get the studio version, but this one looks interesting.  

But I hate to say it, you will never catch me dead anywhere in California. Maybe fifty years ago but not today, even if I could afford the rents there.  

Re: A useful addition to your toolkit
On Wed, 08 Mar 2017 22:58:08 -0800, jurb6006 wrote:

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Certainly did!

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It all seemed to go tits-up right at the dog-end of 1969, around the time  
of the Alta Mont free concert and that awful business involving Charlie  
Manson and his 'Family' - and never recovered. :(


Re: A useful addition to your toolkit
John Larkin wrote:
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There's one on ebay now for $750.




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Re: A useful addition to your toolkit
John Larkin wrote:
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I once asked if a discarded head from an old, old hard disk could do  
that.

There used to be a four-pin probe for PCB current measurement, in the  
late 80s, but I can't find it.  They're probably on ebay but I don't  
know what name to search for.




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Re: A useful addition to your toolkit
On 05/03/2017 15:44, John Larkin wrote:
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Tell that to a condition monitoring engineer!



Re: A useful addition to your toolkit
wrote:

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I don't design AC power supplies any more. I can buy an entire nice
PFC switcher for less than I could buy a 60 Hz power transformer.
Since the supplies all come with UL/CE/VDE/etc stickers, I don't care
about their input current waveforms.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: A useful addition to your toolkit
On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin

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I generally use a ferrite (pi filter) on the supplies to uCs and DSPs
for EMI, then substitute a shunt to measure the power during test.
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The old HP current probe was a great debugging tool.

Re: A useful addition to your toolkit
On 06/03/2017 00:41, snipped-for-privacy@notreal.com wrote:
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+1 I'd love an HP-547A

piglet


Re: A useful addition to your toolkit
John Larkin wrote:

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** Mains current waveforms are VERY interesting, but not if all you can see is 60Hz. A Hall effect transducer is needed to do the job properly.  

The one is use is by LEM and has response to 100kHz, allows me to see currents as low as 1mA and up to 100A peak.  


....  Phil  

Re: A useful addition to your toolkit
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I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
on boards.

Greg

Re: A useful addition to your toolkit
wrote:

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Yes, but have you seen the prices?
<http://www.tek.com/current-probe
The cheapest model that does DC is $1,600.

I rolled my own.  I took an old Honeywell SS495A Hall effect sensor,
built a suitable amplifier, hot melt glued it to a piece of plastic,
and calibrated it by shoving DC through various PCB traces.  It's
ugly, not very sensitive (3mv/gauss or 30uV/uT), and goes nuts near
magnetic fields from xformers, inductors, steel mounting brackets,
wall warts, etc.  However, it's cheap and easy.  I don't use it for
troubleshooting very often.

The original suggestion sounds much like an RF current probe.
<http://www.lowfer.us/k0lr/currprob/currprob.htm
<https://interferencetechnology.com/the-hf-current-probe-theory-and-application/
However, these cannot be used to measure current though a PCB trace.



--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: A useful addition to your toolkit
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I was using a NASA owned probe. Thought about trying to make one.

Greg

Re: A useful addition to your toolkit
John Larkin wrote:
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   You just described that PCB trace current probe; just use known trace  
length - with known width you get approximate current.

Re: A useful addition to your toolkit
On Thu, 09 Mar 2017 22:43:29 -0800, Robert Baer

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I do that. But multi-layer power pours are not such well-defined
resistors.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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