A useful addition to your toolkit

"Winfield Hill" <hill@rowland.harvard.edu> wrote in message
news:eek:9l4j601vp8@drn.newsguy.com...
John Larkin wrote...

We just demoed a cool new thermal imager ...

Names, please. And results, later.


--
Thanks,
- Win
Click to expand...

We don't believe it until there are pictures.
 
On 6 Mar 2017 18:06:30 -0800, Winfield Hill <hill@rowland.harvard.edu>
wrote:

John Larkin wrote...

We just demoed a cool new thermal imager ...

Names, please. And results, later.
Click to expand...

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
 
Phil Allison <pallison49@gmail.com> wrote:
John Larkin wrote:



I have a clamp-on ammeter that pretty much does that, although it just
indicates amps, and doesn't allow waveform snooping. 60 Hz waveforms
aren't terribly interesting.


** 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
Click to expand...

I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
on boards.

Greg
 
On Mon, 06 Mar 2017 20:56:02 -0500, Michael A. Terrell wrote:

Let's see you use it to find a stray 100 mA DC on a crowded circuit
board. :(
Click to expand...

Oh come along now. You know it's not intended for that sort of usage!
 
On Tue, 7 Mar 2017 09:11:34 -0000 (UTC), gregz <zekor@comcast.net>
wrote:

I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
on boards.
Greg
Click to expand...

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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Tue, 7 Mar 2017 09:11:34 -0000 (UTC), gregz <zekor@comcast.net
wrote:

I used to like using a Tek Hall sensor probe. I liked it checking DC shorts
on boards.
Greg

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.
Click to expand...

I was using a NASA owned probe. Thought about trying to make one.

Greg
 
On Wed, 08 Mar 2017 05:44:39 -0800, Winfield Hill wrote:

I ordered one from Newark, and plan to use it on my messed-up switching
power-supply designs.
Qualitative results will be fine.
Click to expand...

Mine arrived today. I plan to monitor fuel injection impulses with it
firstly just to see what kind of di/dt responses it's capable of. I'm not
quite as confident as you are, though!
 
Cursitor Doom wrote...
Michael A. Terrell wrote:

Let's see you use it to find a stray 100 mA DC
on a crowded circuit board. :(

Oh come along now. You know it's not intended for
that sort of usage!
Click to expand...

I ordered one from Newark, and plan to use it
on my messed-up switching power-supply designs.
Qualitative results will be fine.


--
Thanks,
- Win
 
Cursitor Doom wrote...
On Wed, 08 Mar 2017 05:44:39 -0800, Winfield Hill wrote:

I ordered one from Newark, and plan to use it on my messed-up switching
power-supply designs.
Qualitative results will be fine.

Mine arrived today. I plan to monitor fuel injection
impulses with it firstly just to see what kind of
di/dt responses it's capable of. I'm not quite as
confident as you are, though!
Click to expand...

I do a lot of fast HV pulsing circuitry, and don't
expect it'll be helpful for that kind of work. But
the 5MHz bandwidth should be fine for looking at
inductor current ramps, cap charge-discharge, etc.


--
Thanks,
- Win
 
On 2017-03-08, Winfield Hill <hill@rowland.harvard.edu> wrote:
Cursitor Doom wrote...

Michael A. Terrell wrote:

Let's see you use it to find a stray 100 mA DC
on a crowded circuit board. :(

Oh come along now. You know it's not intended for
that sort of usage!

I ordered one from Newark, and plan to use it
on my messed-up switching power-supply designs.
Qualitative results will be fine.
Click to expand...

a few years back there was talk of using a video head from a VCR
(after removing it from the drum) to probe AC currents. It should be good
to a few megahertz. a core from an ethernet transformer with a gap
added could be another option. a spool-shaped inductor would
probably work too.


--
This email has not been checked by half-arsed antivirus software
 
On 8 Mar 2017 18:53:52 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2017-03-08, Winfield Hill <hill@rowland.harvard.edu> wrote:
Cursitor Doom wrote...

Michael A. Terrell wrote:

Let's see you use it to find a stray 100 mA DC
on a crowded circuit board. :(

Oh come along now. You know it's not intended for
that sort of usage!

I ordered one from Newark, and plan to use it
on my messed-up switching power-supply designs.
Qualitative results will be fine.

a few years back there was talk of using a video head from a VCR
(after removing it from the drum) to probe AC currents. It should be good
to a few megahertz. a core from an ethernet transformer with a gap
added could be another option. a spool-shaped inductor would
probably work too.
Click to expand...

A little unshielded drum-core inductor is a handy h-field probe.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Tuesday, March 7, 2017 at 1:21:14 PM UTC-5, Cursitor Doom wrote:
On Mon, 06 Mar 2017 20:56:00 -0800, John Larkin wrote:

Or maybe they just like
coming to San Francisco.

Unlikely. ;-
Click to expand...

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.
 
John Larkin wrote:
On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

https://www.sparkfun.com/products/11005

Replace the existing connector with a BNC, add a bit of series
resistance and you have a *very* cheap current probe for your
scope.

I have a clamp-on ammeter that pretty much does that, although it
just indicates amps, and doesn't allow waveform snooping. 60 Hz
waveforms aren't terribly interesting.

My real problem with current measurement is DC, on PC boards. We
want to know how much current, say, an FPGA is using. Sometimes I
include current shunts in a layout, but sometimes I don't.

One can use existing switcher inductors as current shunts. I wish I
had a PCB trace current probe, but that's probably not posssible.
You can measure millivolt and microvolt drops across traces and
vias.
Click to expand...
You just described that PCB trace current probe; just use known trace
length - with known width you get approximate current.
 
On Thu, 09 Mar 2017 22:43:29 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

John Larkin wrote:
On Sun, 5 Mar 2017 14:48:51 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

https://www.sparkfun.com/products/11005

Replace the existing connector with a BNC, add a bit of series
resistance and you have a *very* cheap current probe for your
scope.

I have a clamp-on ammeter that pretty much does that, although it
just indicates amps, and doesn't allow waveform snooping. 60 Hz
waveforms aren't terribly interesting.

My real problem with current measurement is DC, on PC boards. We
want to know how much current, say, an FPGA is using. Sometimes I
include current shunts in a layout, but sometimes I don't.

One can use existing switcher inductors as current shunts. I wish I
had a PCB trace current probe, but that's probably not posssible.
You can measure millivolt and microvolt drops across traces and
vias.




You just described that PCB trace current probe; just use known trace
length - with known width you get approximate current.
Click to expand...

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


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Wed, 08 Mar 2017 22:58:08 -0800, jurb6006 wrote:

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

Certainly did!

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.
Click to expand...

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. :(
 
John Larkin wrote:
On Sun, 5 Mar 2017 16:18:50 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sun, 05 Mar 2017 07:44:18 -0800, John Larkin wrote:

I have a clamp-on ammeter that pretty much does that, although it
just indicates amps, and doesn't allow waveform snooping. 60 Hz
waveforms aren't terribly interesting.

Indeed they're not. But your meter is presumably *only* designed for
use at 60Hz, I would imagine. Hook it up to a 100Hz signal and
you'll see nothing at all in all probability. ;-)

One can use existing switcher inductors as current shunts. I wish I
had a PCB trace current probe, but that's probably not posssible.
You can measure millivolt and microvolt drops across traces and
vias.

Do they even exist? That would be amazing but no doubt *way* beyond
what I can justify to splash out on as a mere hobbyist.


A 1" long, 20 mil wide 1oz trace will be about 25 milliohms. 1 amp
makes 25 millivolts, and lots of cheapish DVMs will resolve that well
enough. You probably need a bench DVM with microvolt resolution to
measure, say, 1 amp running through a via, but you could build a
little microvolt meter or amp pretty easily. PCB trace and via
resistances need to be calibrated, which is only a minor nuisance.

Here are some pcb-trace shunts, down near the connector:

https://dl.dropboxusercontent.com/u/53724080/PCBs/TEM2_Power_Board.JPG

One of the great mysteries of electronics is "where is the current
going?" Sometimes a thermal imager helps figure that out. A little
magnetometer would be fun, not hard to do these days.
Click to expand...

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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John Larkin wrote:
On Sun, 5 Mar 2017 15:07:41 -0600, Foxs Mercantile <jdangus@att.net
wrote:

They do make special current probes specifically for doing traces
on a PC board. without cutting traces or requiring a loop of wire.
http://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf

Looks expensive, and I'd guess not very accurate.
Click to expand...

There's one on ebay now for $750.




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