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'[EE]: Shunt'
2002\12\09@185709 by PicDude

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A shunt is marked "50mV" and "150A".  Does this mean that the
resistance is such that 150A passing thru it will produce a
50mV drop?  I can't think of any other explanation.

Cheers,
-Neil.

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2002\12\09@191842 by Jim

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Can you test it?

(At some point you will HAVE to - right?)

RF Jim


----- Original Message -----
From: "PicDude" <spam_OUTpicdudeTakeThisOuTspamNARWANI.ORG>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Monday, December 09, 2002 5:44 PM
Subject: [EE]: Shunt


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2002\12\09@192006 by Larry Bradley

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Yes, that's exactly what it means.

Larry

At 05:44 PM 12/9/2002 -0600, you wrote:
{Quote hidden}

Larry Bradley
Orleans (Ottawa), Ontario, CANADA

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2002\12\09@193725 by Spehro Pefhany

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At 05:44 PM 12/9/02 -0600, you wrote:
>A shunt is marked "50mV" and "150A".  Does this mean that the
>resistance is such that 150A passing thru it will produce a
>50mV drop?

Yes. 50mV/60mV/100mV/150mV are common.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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2002\12\09@194556 by Rich

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Yes!
----- Original Message -----
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Sent: Monday, December 09, 2002 7:10 PM
Subject: Re: [EE]: Shunt


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2002\12\09@194738 by Rich

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It will be linear. so you can plot a few points and extrapolate or regress
the equation.
----- Original Message -----
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Sent: Monday, December 09, 2002 7:06 PM
Subject: Re: [EE]: Shunt


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2002\12\09@200020 by Jim

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I still say he need *only* 'characterize' a portion
of the conductors in whatever beast of an application
he's got - and use that as the 'current measuring
apparatus' as opposed to the seemingly unwieldly
task of 'breaking' a high current circuit.

I have usd this trick before to measure starter
current draw on a car - first apply something on
the order of a 10 Amp load and record the voltage
drop across a convenient portion of 'exposed' high
current cable.

I have even used small needles to puncture the
high-current batt cables at convenient points for
"unobtrusive" and "non-invasive" measurements ...

RF Jim



{Original Message removed}

2002\12\09@202520 by Andy Kunz

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You are correct, it works quite well, Jim.  I've done it myself for a long
time this way.  The key is to make sure you keep the thermal response
figure out, or you have major problems.

Bob Pease just wrote about this not too long ago in his monthly column.

But if he already HAS a shunt, he should use it.  I use .1% shunts for
2000A 50mV at work in some products.  Talk about bucks!!!

Andy

At 06:58 PM 12/9/02 -0600, you wrote:
{Quote hidden}

>{Original Message removed}

2002\12\09@203602 by PicDude

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Jim wrote:
>
> Can you test it?
>
Nope.  Don't actually have one.  Just saw one.

>
> (At some point you will HAVE to - right?)
>

Nope.  Unless I actually buy one. :-)

Cheers,
-Neil.

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2002\12\10@031640 by PicDude

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Rich wrote:
> Yes!


Larry wrote:
> Yes, that's exactly what it means.


Spehro Pefhany wrote:
> Yes. 50mV/60mV/100mV/150mV are common.


Excellent. Thanks.
-Neil.

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2002\12\10@031745 by PicDude

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This is an excellent way to do this (which I believe was
also discussed on this list some months ago), but again,
I was just asking the question as I saw these in a store
today.  There is no beast of an application.  Sorry to
disappoint you.

However, I am about to embark upon the construction of a
current measurement system for an ATX PS.  Max current
expected on any line is 3A.  For this, I am going to use
sense resistors of .01ohm, 1W.  No beast in that. :-)

Cheers,
-Neil.



Jim wrote:
{Quote hidden}

> {Original Message removed}

2002\12\10@031753 by PicDude

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What the &#%*$@! generates 2000A?



Andy Kunz wrote:
{Quote hidden}

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2002\12\10@033434 by Ashley Roll

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"Whole of Building" UPS battery Banks?
Electric Traction motors on Trains?
Electric Drag Cars?
Experimental Fusion Reactors?

Plasma generating spanners or screwdrivers in inappropriate locations. :)

Cheers,
Ash.

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> {Original Message removed}

2002\12\10@042103 by Roman Black

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PicDude wrote:
>
> What the &#%*$@! generates 2000A?


The sub station. ;o)

I worked on DC cranes (overhead beam cranes) in heavy
industry, DC traction motors each 400v, hundreds
of amps and sized about 1m diam and 1.5m long.
Relay copper contacts bigger then your fist, and my
favorite the resistors used for the 3 traction speeds
(no PWM then!) were cast iron and the size of cars!
Each made from cast iron "snakes" about the size
of a skateboard and barely liftable, bolted together
to make an air cooled resistor the size of a car in
a wire cage. I'm guessing 1 megawatt resistor? Most
stuff was oversized with an "industrial" safety
margin. I carried some of those resistor snakes up
many flights of greasy metal stairs to the crane,
not a fun job. These cranes were about 20 ton load
max, the steelworks slab yard had the REALLY big
cranes, 120 ton and up... You can imagine the stories
from those guys!!
:o)
-Roman

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2002\12\10@055503 by Andy Kunz

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At 01:51 AM 12/10/02 -0600, you wrote:
>What the &#%*$@! generates 2000A?

What SUCKS 2000A is more like the question.

It's for telcom power.  -48V of lead acid batteries, with plates > 1 foot
square, in parallel is the backup power.  Basically, we make giant UPS's
for the phone companies.

We have 12.5KA systems we've built (12.5KA x 54V (typical float voltage) =
675000 Watts!

http://www.tdipower.com

What's really cools is we measure 2000A currents flowing OUT of the
batteries, but on the same shunt we will make float charge currents in the
milliamps _accurately_.  The analog circuitry is way up there - the Analog
guys in Ireland spent a lot of time on the phone with us when we made that
product!

Andy

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2002\12\10@055508 by Andy Kunz

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>Plasma generating spanners or screwdrivers in inappropriate locations. :)

Those go way over 2000A, but only for a few milliseconds as the iron is
converted to iron oxide gas and then dissipates. ;)

Andy

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2002\12\10@065122 by Justin Grimm

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I used to work at an aluminium smelter that had 95000 amp busbars for the
smelting process...

Justin

{Original Message removed}

2002\12\10@090121 by Jim

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I bought a used HP clip-on DC ammeter to to this
kind of thing (current measurement on a PC's power
supply). I like 'unobtrusive', easy measurments where
possible!

On the matter of the large shunt -

One (such as myself) always assumes the worst when one
begins to see current levels of 150 Amps, Neil - for all
we knew you were going to parallel a commmunicvations
tower and measure a fraction of the lightning current
present during a lightning hit (they make such things
as 'hit detectors' for that application BTW)!

RF Jim

{Original Message removed}

2002\12\10@092700 by Larry Bradley

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Wimp!  REAL men measure HUNDREDS of amps   :)


At 01:49 AM 12/10/2002 -0600, you wrote:
 ...

>However, I am about to embark upon the construction of a
>current measurement system for an ATX PS.  Max current
>expected on any line is 3A.  For this, I am going to use
>sense resistors of .01ohm, 1W.  No beast in that. :-)
>
>Cheers,
>-Neil.
>
>

Larry Bradley
Orleans (Ottawa), Ontario, CANADA

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2002\12\10@094540 by Spehro Pefhany

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At 09:26 AM 12/10/02 -0500, you wrote:
>Wimp!  REAL men measure HUNDREDS of amps   :)

We did a nice panel full (about 30) of digital ammeters, the highest
range was 15,000 A, the lowest 2000A. And this was process control, not
switchgear.

As someone pointed out, when you get into things like making aluminum,
it gets really impressive. They tend to put the factories close to the
power sources.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spamBeGonespeffspamBeGonespaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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2002\12\10@102354 by Jim

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Instantanously or continuously?

Sometimes the average power is measured in only
watts or hundreds of watts (with the corresponding
current and voltage levels) but the PEAK power/current
can be thousands that average value (depending on the
duty cycle which is dependent on PW - pulse width
and PRF - pulse repitition frequency).


RF Jim

{Original Message removed}

2002\12\10@112218 by William Chops Westfield

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A car battery will sustain a current of 1000A "long enough to melt a
screwdriver."

BillW

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2002\12\10@121445 by Claudio Tagliola

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> A car battery will sustain a current of 1000A "long enough to melt a
> screwdriver"

and you'll receive a one way ticket to the recycling company as a bonus.

:)

However, I've heard stories of reviving a long-dead battery by shorting it
which reversed polarity and restored it's ability to recharge. Never tried
it
though, could be bullwhack talk.

Best regards,
Claudio

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2002\12\10@123429 by Peter L. Peres

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On Tue, 10 Dec 2002, PicDude wrote:

*>sense resistors of .01ohm, 1W.  No beast in that. :-)

The beast is in the differential sensing in the presence of switching
noise.

good luck,

Peter

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2002\12\10@140429 by hard Prosser

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You can add telephone exchange equipment to the list also. - We do systems
>6000A (Although 50mV shunts get a bit warm on this!)
Richard P



"Whole of Building" UPS battery Banks?
Electric Traction motors on Trains?
Electric Drag Cars?
Experimental Fusion Reactors?

Plasma generating spanners or screwdrivers in inappropriate locations. :)

Cheers,
Ash.

---
Ashley Roll
Digital Nemesis Pty Ltd
http://www.digitalnemesis.com
Mobile: +61 (0)417 705 718




> {Original Message removed}

2002\12\10@143107 by Peter L. Peres

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On Wed, 11 Dec 2002, Richard Prosser wrote:

*>You can add telephone exchange equipment to the list also. - We do systems
*>>6000A (Although 50mV shunts get a bit warm on this!)
*>Richard P

And just about any electric forklift truck will compete here. Esp.
starting current.

Peter

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2002\12\10@162043 by Chris Hunter

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----- Original Message -----
From: "Larry Bradley" <TakeThisOuTlhbradleyEraseMEspamspam_OUTIGS.NET>
To: <RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Tuesday, December 10, 2002 2:26 PM
Subject: Re: [EE]: Shunt


> Wimp!  REAL men measure HUNDREDS of amps   :)

My Father is a power station engineer, and derisively calls me a "milliamp
man" as I only do (low current!) electronic design.

Chris

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2002\12\10@231511 by Rich

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Some transients are much greater than 2000A.
Rich
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Sent: Tuesday, December 10, 2002 5:47 AM
Subject: Re: [EE]: Shunt


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2002\12\10@232135 by Rich

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I could prove it but I discarded the screw driver.  The end was useless.
Rich
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Sent: Tuesday, December 10, 2002 11:20 AM
Subject: Re: [EE]: Shunt


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