making a mag field

[George Herold]

On Wednesday, December 18, 2013 2:03:03 PM UTC-5, John Larkin wrote:

On Wed, 18 Dec 2013 10:30:35 -0800 (PST), George Herold

gherold@teachspin.com> wrote:

Something like this from Pasco?

http://www.pasco.com/prodCatalog/EM/EM-8618_variable-gap-magnet/



That's cool. The gap is plenty big, but I can't tell if we could get
the field down to 600 gauss. Given that example, the idea of putting
magnets on the face of a vise looks practical.

Add pieces of iron to the pole face as a field 'spreader'. That should get the field down. I'd order the gizmo from pasco. $200 is not that much if it will get close to what you want. You could easily blow ~$200 playing around with the vise idea.... (and you've got to hold the magents to the vise.. or 'look out'!)

We'd need a gaussmeter, not a bad thing to have anyhow.

(I can't imagine why our customer would expect a VME module to ever
see a 600 gauss field.)

Hmm, fringing fields outside of a super conducting magnet?

George H.

Thanks





--



John Larkin Highland Technology, Inc



jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com



Precision electronic instrumentation

Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

VME thermocouple, LVDT, synchro acquisition and simulation

 

[George Herold]

On Thursday, December 19, 2013 10:27:25 AM UTC-5, John Larkin wrote:

On Thu, 19 Dec 2013 06:23:16 -0800 (PST), George Herold <gherold@teachspin.com

wrote:


Add pieces of iron to the pole face as a field 'spreader'. That should get the field down. I'd order the gizmo from pasco. $200 is not that much if it will get close to what you want. You could easily blow ~$200 playing around with the vise idea.... (and you've got to hold the magents to the vise.. or 'look out'!)


Yeah, I'd have to epoxy or weld the magnets to the jaws of the vise, otherwise
they'd fall off?
Well no, They'll stick to the iron. But it's my impression that if the pole pieces get too close together they'll be pulled off of the iron...maybe this is not correct? (I'm a little afraid to try the experiment.) But perhaps you'll give it a whirl and let us know.

George H.

--



John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com



Precision electronic instrumentation

Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

VME analog, thermocouple, LVDT, synchro, tachometer

Multichannel arbitrary waveform generators

 

[RobertMacy]

On Wed, 18 Dec 2013 18:14:56 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

....snip....
6000 a-t sounds like a lot of work.

I ordered the $180 ebay field meter that Lasse suggested. I think I'll
try putting lots of little round supermagnets on the faces of a
machinist's vise, which should have a pretty good magnetic circuit.
George's Pasco link suggests that that might work.

I'll post pics.

We had a permanent magnet and an electromagnetic that produed about 0.5T
hrough a gap of 1 inch with a face about 4 by 4 inches at least.

The thing weighed 1800 pounds and the electromagnetic had water cooled
wiring taking something like 3 kW

Do you have access to any friends working in ion implantation? Somewhere
in Silicon Valley should be a source. The magnetic fields those thing
generate with a control of better than 0.1% would do your task easily.

 

[RobertMacy]

On Wed, 18 Dec 2013 10:53:01 -0700, John Larkin
<jjlarkin@highnotlandthistechnologypart.com> wrote:

We have a requirement to design a gadget that will work in a 0.06T static
magnetic field, and we want to use some miniature telecom type relays.
They are
not specified for field tolerance. So we need to make such a field and
test
them.

...snip...

John,

From memory, don't those relays activate in a 20mT field? In other words,
all your OPEN relays will CLOSE in that strong a field. Right?

Anyway, bet once you 'qualify' those relays to sit in a static field; your
customer will admit that the field migh possibly change once in a while
and you'll have to qualify for ramp up/ramp down too. and maybe overshoot,
etc etc.

Is the field guarranteed to be somewhere? Like some orientation? A field
that value just can't be omnidirectional. Therefore you can 'shadow' the
field down by placing adjacent metal pieces made from standard transformer
leaves. Can check, but they should handle that level of field AND suck the
field over to themselves, providing a 'bypass' away from your relays, with
that much lower field, you could then properly shield the relays in
mumetal, or such, and really drop what the relay 'sees'.

 

[Anthony Stewart]

0.06T is pretty benign compared to >1.5T used in most transformer steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative performance effects?

Go for broke and test to 1T with permanent magnets and assess if you need to lower the level.

Most failures will occur from changing magnetic fields not static. Unless you are testing Rats or Reed Relays.

 

[John Larkin]

On Thu, 19 Dec 2013 06:23:16 -0800 (PST), George Herold <gherold@teachspin.com>
wrote:

On Wednesday, December 18, 2013 2:03:03 PM UTC-5, John Larkin wrote:
On Wed, 18 Dec 2013 10:30:35 -0800 (PST), George Herold

gherold@teachspin.com> wrote:

Something like this from Pasco?

http://www.pasco.com/prodCatalog/EM/EM-8618_variable-gap-magnet/



That's cool. The gap is plenty big, but I can't tell if we could get
the field down to 600 gauss. Given that example, the idea of putting
magnets on the face of a vise looks practical.

Add pieces of iron to the pole face as a field 'spreader'. That should get the field down. I'd order the gizmo from pasco. $200 is not that much if it will get close to what you want. You could easily blow ~$200 playing around with the vise idea.... (and you've got to hold the magents to the vise.. or 'look out'!)

Yeah, I'd have to epoxy or weld the magnets to the jaws of the vise, otherwise
they'd fall off?


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[John Larkin]

On Thu, 19 Dec 2013 07:59:03 -0800 (PST), George Herold <gherold@teachspin.com>
wrote:

On Thursday, December 19, 2013 10:27:25 AM UTC-5, John Larkin wrote:
On Thu, 19 Dec 2013 06:23:16 -0800 (PST), George Herold <gherold@teachspin.com

wrote:


Add pieces of iron to the pole face as a field 'spreader'. That should get the field down. I'd order the gizmo from pasco. $200 is not that much if it will get close to what you want. You could easily blow ~$200 playing around with the vise idea.... (and you've got to hold the magents to the vise.. or 'look out'!)


Yeah, I'd have to epoxy or weld the magnets to the jaws of the vise, otherwise
they'd fall off?
Well no, They'll stick to the iron. But it's my impression that if the pole pieces get too close together they'll be pulled off of the iron...maybe this is not correct? (I'm a little afraid to try the experiment.) But perhaps you'll give it a whirl and let us know.

I wasn't planning to close the jaws on the magnets, but I might try that. I'd
expect that, if two magnets touched, the attraction between magnets would be
more than magnet-to-steel, so if one then opened the jaws one side of the stuck
pair would pull off one jaw. Maybe.

It'll take a couple of weeks for my field meter to show up.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Spehro Pefhany]

On Thu, 19 Dec 2013 07:27:25 -0800, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Thu, 19 Dec 2013 06:23:16 -0800 (PST), George Herold <gherold@teachspin.com
wrote:

On Wednesday, December 18, 2013 2:03:03 PM UTC-5, John Larkin wrote:
On Wed, 18 Dec 2013 10:30:35 -0800 (PST), George Herold

gherold@teachspin.com> wrote:

Something like this from Pasco?

http://www.pasco.com/prodCatalog/EM/EM-8618_variable-gap-magnet/



That's cool. The gap is plenty big, but I can't tell if we could get
the field down to 600 gauss. Given that example, the idea of putting
magnets on the face of a vise looks practical.

Add pieces of iron to the pole face as a field 'spreader'. That should get the field down. I'd order the gizmo from pasco. $200 is not that much if it will get close to what you want. You could easily blow ~$200 playing around with the vise idea.... (and you've got to hold the magents to the vise.. or 'look out'!)

Yeah, I'd have to epoxy or weld the magnets to the jaws of the vise, otherwise
they'd fall off?

Big magnets can take a nasty nip out of a finger or, as I've had
happen, shatter when they slam themselves together.

 

[John Larkin]

On Thu, 19 Dec 2013 11:49:02 -0800 (PST), Anthony Stewart
<tony.sunnysky@gmail.com> wrote:

0.06T is pretty benign compared to >1.5T used in most transformer steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative performance effects?

The customer spec says that the board has to work in fields up to 600 gauss. I
don't see how that's going to happen in a VME crate. Our first plan is to try to
talk them out of it.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Greegor]

I've seen it happen around big physics experiments. Specifically,
I measured about 100mT around some big LEP experiments, and that
was just the leakage. Very hard to shield.
Ideally, you want your electronics away from the field, but in
an underground area, you can go only so far in any direction.
Jeroen Belleman

This is similar to EMP protection right?
If you can't get distance, wouldn't welded iron plate boxes be good?
Wouldn't wires going in and out of the box become generators?

 

[Bill Sloman]

On Friday, 20 December 2013 21:13:58 UTC+11, Greegor wrote:

I've seen it happen around big physics experiments. Specifically, I measured about 100mT around some big LEP experiments, and that was just the leakage. Very hard to shield.

Ideally, you want your electronics away from the field, but in an underground area, you can go only so far in any direction.

This is similar to EMP protection right?

Wrong. This thread is about static magnetic fields, not electromagnetic pulses.

If you can't get distance, wouldn't welded iron plate boxes be good?
Wouldn't wires going in and out of the box become generators?

Not with a static magnetic field.

John Larkin has said that his board has to work inside a VME crate, so it's difficult to imagine where the welded iron plates might go, and how they might shield the relays from the external flux.

If the flux was strictly through the board. you could put a Hall effect field sensor or two fairly close to the relay and have a coil in the plane of the board to generate a counter-acting flux, so that the Hall sensors see essentially zero net flux at the relay, but setting up two extra orthogonal coils and sets of sensors to null the field in all three dimensions would get messy.

Solid state relays might be an easier solution.

--
Bill Sloman, Sydney

 

[Jeroen Belleman]

On 2013-12-20 04:42, John Larkin wrote:

On Thu, 19 Dec 2013 11:49:02 -0800 (PST), Anthony Stewart
tony.sunnysky@gmail.com> wrote:

0.06T is pretty benign compared to >1.5T used in most transformer
steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative
performance effects?

The customer spec says that the board has to work in fields up to 600
gauss. I don't see how that's going to happen in a VME crate. Our
first plan is to try to talk them out of it.

I've seen it happen around big physics experiments. Specifically,
I measured about 100mT around some big LEP experiments, and that
was just the leakage. Very hard to shield.

Ideally, you want your electronics away from the field, but in
an underground area, you can go only so far in any direction.

Jeroen Belleman

 

[John Larkin]

On Fri, 20 Dec 2013 09:05:03 +0100, Jeroen Belleman <jeroen@nospam.please>
wrote:

On 2013-12-20 04:42, John Larkin wrote:
On Thu, 19 Dec 2013 11:49:02 -0800 (PST), Anthony Stewart
tony.sunnysky@gmail.com> wrote:

0.06T is pretty benign compared to >1.5T used in most transformer
steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative
performance effects?

The customer spec says that the board has to work in fields up to 600
gauss. I don't see how that's going to happen in a VME crate. Our
first plan is to try to talk them out of it.



I've seen it happen around big physics experiments. Specifically,
I measured about 100mT around some big LEP experiments, and that
was just the leakage. Very hard to shield.

Ideally, you want your electronics away from the field, but in
an underground area, you can go only so far in any direction.

Jeroen Belleman

The only problem would be the relays, which would be used for BIST, self-test of
the input channels.

My ebay field meter has been shipped, so I can test some relays after the New
Year break.



--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[John Larkin]

On Fri, 20 Dec 2013 09:05:03 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 2013-12-20 04:42, John Larkin wrote:
On Thu, 19 Dec 2013 11:49:02 -0800 (PST), Anthony Stewart
tony.sunnysky@gmail.com> wrote:

0.06T is pretty benign compared to >1.5T used in most transformer
steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative
performance effects?

The customer spec says that the board has to work in fields up to 600
gauss. I don't see how that's going to happen in a VME crate. Our
first plan is to try to talk them out of it.



I've seen it happen around big physics experiments. Specifically,
I measured about 100mT around some big LEP experiments, and that
was just the leakage. Very hard to shield.

Ideally, you want your electronics away from the field, but in
an underground area, you can go only so far in any direction.

Jeroen Belleman

One of my customers has a conference room with a chain of paper clips
with one end stuck to one wall, sticking out a foot or so at about a
45 degree angle. In the next room is an unshielded 600 MHz NMR magnet.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

 

[Jon Elson]

John Larkin wrote:

(I can't imagine why our customer would expect a VME module to ever
see a 600 gauss field.)

600 g on an entire VME crate? Will the magnetics in the switching
power supplies work right in a 600 g field? I'd have big doubts.
Will the fans on the crate still turn, or will they either
bind up, or maybe the field will screw up the Hall sensors in
their motors and make them burn out?

Seems really iffy to have a 600 g field in large equipment like that.
Is this for an MRI suite? They generally keep all electronics possible
out of the magnet room (due to FRI), and have vast mu-metal shields to try
to contain the field.

Jon

 

[Robert Baer]

John Larkin wrote:

On Thu, 19 Dec 2013 06:23:16 -0800 (PST), George Herold<gherold@teachspin.com
wrote:

On Wednesday, December 18, 2013 2:03:03 PM UTC-5, John Larkin wrote:
On Wed, 18 Dec 2013 10:30:35 -0800 (PST), George Herold

gherold@teachspin.com> wrote:

Something like this from Pasco?

http://www.pasco.com/prodCatalog/EM/EM-8618_variable-gap-magnet/



That's cool. The gap is plenty big, but I can't tell if we could get
the field down to 600 gauss. Given that example, the idea of putting
magnets on the face of a vise looks practical.

Add pieces of iron to the pole face as a field 'spreader'. That should get the field down. I'd order the gizmo from pasco. $200 is not that much if it will get close to what you want. You could easily blow ~$200 playing around with the vise idea.... (and you've got to hold the magents to the vise.. or 'look out'!)

Yeah, I'd have to epoxy or weld the magnets to the jaws of the vise, otherwise
they'd fall off?


And welding any magnet will kill it...

 

[Maynard A. Philbrook Jr.]

In article <gq19b9lo61vragmgcbi36k1e3jqv2laopp@4ax.com>,
jlarkin@highlandtechnology.com says...

On Fri, 20 Dec 2013 09:05:03 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2013-12-20 04:42, John Larkin wrote:
On Thu, 19 Dec 2013 11:49:02 -0800 (PST), Anthony Stewart
tony.sunnysky@gmail.com> wrote:

0.06T is pretty benign compared to >1.5T used in most transformer
steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative
performance effects?

The customer spec says that the board has to work in fields up to 600
gauss. I don't see how that's going to happen in a VME crate. Our
first plan is to try to talk them out of it.



I've seen it happen around big physics experiments. Specifically,
I measured about 100mT around some big LEP experiments, and that
was just the leakage. Very hard to shield.

Ideally, you want your electronics away from the field, but in
an underground area, you can go only so far in any direction.

Jeroen Belleman

One of my customers has a conference room with a chain of paper clips
with one end stuck to one wall, sticking out a foot or so at about a
45 degree angle. In the next room is an unshielded 600 MHz NMR magnet.

Not a problem according to an recent article I read, they seem to think
high static meg fields may have some health benefits!

Jamie

 

[Phil Hobbs]

On 12/20/2013 6:53 PM, Maynard A. Philbrook Jr. wrote:

In article <gq19b9lo61vragmgcbi36k1e3jqv2laopp@4ax.com>,
jlarkin@highlandtechnology.com says...

On Fri, 20 Dec 2013 09:05:03 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2013-12-20 04:42, John Larkin wrote:
On Thu, 19 Dec 2013 11:49:02 -0800 (PST), Anthony Stewart
tony.sunnysky@gmail.com> wrote:

0.06T is pretty benign compared to >1.5T used in most transformer
steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative
performance effects?

The customer spec says that the board has to work in fields up to 600
gauss. I don't see how that's going to happen in a VME crate. Our
first plan is to try to talk them out of it.



I've seen it happen around big physics experiments. Specifically,
I measured about 100mT around some big LEP experiments, and that
was just the leakage. Very hard to shield.

Ideally, you want your electronics away from the field, but in
an underground area, you can go only so far in any direction.

Jeroen Belleman

One of my customers has a conference room with a chain of paper clips
with one end stuck to one wall, sticking out a foot or so at about a
45 degree angle. In the next room is an unshielded 600 MHz NMR magnet.

Not a problem according to an recent article I read, they seem to think
high static meg fields may have some health benefits!

Jamie

The only major health effect I've heard of of is capillary ischemia
(restricted blood flow). Apparently red blood cells have a net magnetic
moment, so in a sufficiently strong magnetic field, they want to keep a
particular orientation. They're too large to go sideways through the
smallest capillaries, so they don't.

Cheers

Phil Hobbs

 

[Robert Baer]

Maynard A. Philbrook Jr. wrote:

In article<gq19b9lo61vragmgcbi36k1e3jqv2laopp@4ax.com>,
jlarkin@highlandtechnology.com says...

On Fri, 20 Dec 2013 09:05:03 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2013-12-20 04:42, John Larkin wrote:
On Thu, 19 Dec 2013 11:49:02 -0800 (PST), Anthony Stewart
tony.sunnysky@gmail.com> wrote:

0.06T is pretty benign compared to>1.5T used in most transformer
steel core laminations at rated power.

Do you need to detect this threshold or just not have any negative
performance effects?

The customer spec says that the board has to work in fields up to 600
gauss. I don't see how that's going to happen in a VME crate. Our
first plan is to try to talk them out of it.



I've seen it happen around big physics experiments. Specifically,
I measured about 100mT around some big LEP experiments, and that
was just the leakage. Very hard to shield.

Ideally, you want your electronics away from the field, but in
an underground area, you can go only so far in any direction.

Jeroen Belleman

One of my customers has a conference room with a chain of paper clips
with one end stuck to one wall, sticking out a foot or so at about a
45 degree angle. In the next room is an unshielded 600 MHz NMR magnet.

Not a problem according to an recent article I read, they seem to think
high static meg fields may have some health benefits!

Jamie

The MAGNET for NMR is essentially DC, and a low level RF field inside.
Of course, the MAGNET seems to be "unshielded" as any additional iron
keeper or equivalent would be too big and too expensive and impractical
to properly enclose the field.

 

[DecadentLinuxUserNumeroUn]

On Fri, 20 Dec 2013 02:43:09 -0800 (PST), Bill Sloman
<bill.sloman@gmail.com> Gave us:

This is similar to EMP protection right?

Wrong. This thread is about static magnetic fields, not electromagnetic pulses.

The similarity is when the 'static field' gets its initial generation,
and also when it collapses. If done by a switch, the slew rate is so
fast that it is EXACTLY what an EMP pulse is, just not as powerful.

If the field is natural, it will always be there. If artificially
generated, the rate at which power is applied will determine if there is
a single pulse generated or not, before the standing field is 'up'.