magnetic field

[Robert Baer]

Louis Scheffer wrote:

"Greysky" <greyskynospam@sbcglobal.net> writes:


Anyone know of a reliable way of detecting currents less than one femtoamp
i.e. 1X10^-16 amp full-scale? I figure to perhaps use some instrumentation
amps air wired (no pc board) but have not had much luck getting reliable
readings below about a nano amp - and at this scale, even an accidental
breath can leave a film on the chip that creates a current path that swamps
the signal I am looking for.... some have suggested using lots of acetone
for cleaning the circuits, and using silver (or even gold) solder... others
have suggested measuring for resistance and figuring it from there.... I get
the feeling low current designs seem to be more an art than a science. Any
hints, pointers, or guffaws appreciated. Thanks


There are old instruments called 'electrometers' that are routinely used
in this current range. The application notes associated with them
discuss lots of common problems and how to work around them. See for
example:

www.keithley.com/servlet/Data?id=6584

The usual techniques involve lots of cleaning, guarding (surrounding the
measurement point with wires driven to the same potential), special cables
such as triax, avoiding certain materials (watch out for the photoelectric
effect!), control of humidity (if you can), and so on.

One electron is 1.6x10^-19 coulombs, so 10^16 amps full scale is about
600 electrons/sec full scale. So your measurements will definitely be noisy
and extreme care at controlling leakage will be required.

Lou Scheffer

How many *billion* AMPS???
MeThinks you meant 10^-16 amps!

 

[Watson A.Name - \"Watt Su]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:416324C1.F875CB3B@hotmail.com...

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

I went to the veroboard website

http://www.verotl.com/products/index.cfm?content_id=2424A965-4AF2-433B-9
589A039D35545F5
and found a choice of verious sized boards to choos from. I also
went
to the BISCO website, which is their U.S. distribs, but that was
useless
because they need a part number, like no catalog whatsoever.

According to the Bisco website - they aren't a distributor for Vero
( or APW
).

Vero were bought by APW a few yrs back

http://www.apw.com/aboutAPW/sales/electronicSolutions.jsp

Maybe the California office can help ?


So I'm looking at the URL above, and I don't know which to choose
from.
First off, the only VB I've seen was phenolic, not epoxy, so I guess
I
want to order some of that, since it's easy to work with. And I
know I
want single sided with 0.1" hole spacing. But the SRBP has me
stumped,
I've never heard of it before - must be a U.K. term?

Synthetic resin bonded paper - awful stuff !

They make it in epoxy too which is much nicer.


I found this URL
http://www.plasticshimsandgaskets.co.uk/psg_apps/stage1/srbp.htm
which seems to allude to it being phenolic, but I'm not sure.

So I figured out that the VB # 01-0014 looks like it's a convenient
size, and presumably it's phenolic. Is this a commonly used size?

Dimensions look familiar.

What _is_ the size that one would find in a store?

When hobbyist stores still existed here chances were that they kept
the
smaller panels. Not many ppl need 1/2 a metre of the stuff.

I guess small is relative, but the ones I saw on the websites were 17"
long, nearly a half meter long. So I figured that the commonly used
ones were smaller than that, like 4" by 6" (10 by 16 mm) or so.

Anyway, after trying several sites that had it, but none that would show
me what to buy or let me order, I finally just gave Futurlec a try, and
they had both the 4" square and 2" by 4" sizes for about $2 and $1
respectively, so I ordered fifty bucks' worth. They should be here next
week. They seemed to be cheaper than the others, too.

Thanks for all the help.

> Graham

 

[Clarence]

"tejas" <tbsheth@yahoo.co.in> wrote in message
news:68a6c6ef.0410061012.49201ed7@posting.google.com...

http://www.geocities.com/tbsheth

FREE HELP FOR EXAM & QUIZ

I welcome all electronics engineering.
I want to give a large callection of engineering question. on my site
you find 12 different subjects related to electronics engineering
feild.you will find anloge electronics, digital electronics, antennas,
power electronics, optical electronics,engineering
materials,electronics communication. i update my site every week so
keep looking for new quastion .

TROLL....

 

[Louis Scheffer]

"Greysky" <greyskynospam@sbcglobal.net> writes:

Anyone know of a reliable way of detecting currents less than one femtoamp
i.e. 1X10^-16 amp full-scale? I figure to perhaps use some instrumentation
amps air wired (no pc board) but have not had much luck getting reliable
readings below about a nano amp - and at this scale, even an accidental
breath can leave a film on the chip that creates a current path that swamps
the signal I am looking for.... some have suggested using lots of acetone
for cleaning the circuits, and using silver (or even gold) solder... others
have suggested measuring for resistance and figuring it from there.... I get
the feeling low current designs seem to be more an art than a science. Any
hints, pointers, or guffaws appreciated. Thanks

There are old instruments called 'electrometers' that are routinely used
in this current range. The application notes associated with them
discuss lots of common problems and how to work around them. See for
example:

www.keithley.com/servlet/Data?id=6584

The usual techniques involve lots of cleaning, guarding (surrounding the
measurement point with wires driven to the same potential), special cables
such as triax, avoiding certain materials (watch out for the photoelectric
effect!), control of humidity (if you can), and so on.

One electron is 1.6x10^-19 coulombs, so 10^16 amps full scale is about
600 electrons/sec full scale. So your measurements will definitely be noisy
and extreme care at controlling leakage will be required.

Lou Scheffer

 

[Watson A.Name - \"Watt Su]

"Greysky" <greyskynospam@sbcglobal.net> wrote in message
news:hjt8d.6675$nj.2550@newssvr13.news.prodigy.com...

Anyone know of a reliable way of detecting currents less than one
femtoamp
i.e. 1X10^-16 amp full-scale? I figure to perhaps use some
instrumentation

Let's see..
1 mA = 10^-3
1 uA = 10^-6
1 nA = 10^-9
1 pA = 10^-12
1 fA = 10^-15 _not_ 10^-16!

[snip]

Greysky

 

[Watson A.Name - \"Watt Su]

"Nicholas O. Lindan" <see@sig.com> wrote in message
news:TGy8d.4395$Vm1.3257@newsread3.news.atl.earthlink.net...

"Greysky" <greyskynospam@sbcglobal.net> wrote

Anyone know of a reliable way of detecting currents less than one
femtoamp
i.e. 1X10^-16 amp full-scale?

Look under 'electrometers'.

1 fA = 1e-15, ?. Are you looking for 0.1 fA FS?

1A = 6.2e18 electrons/second.
1fA = 6,200 electrons/second.

You are not looking at current, you are counting electrons/second.

Some engineer! No matter what the number of electrons, it's still a
current.

It can be done, however.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.

 

[Watson A.Name - \"Watt Su]

"Louis Scheffer" <lou@cadence.com> wrote in message
news:4162bb53$1@news.cadence.com...

"Greysky" <greyskynospam@sbcglobal.net> writes:

Anyone know of a reliable way of detecting currents less than one
femtoamp
i.e. 1X10^-16 amp full-scale? I figure to perhaps use some
instrumentation
amps air wired (no pc board) but have not had much luck getting
reliable
readings below about a nano amp - and at this scale, even an
accidental
breath can leave a film on the chip that creates a current path that
swamps
the signal I am looking for.... some have suggested using lots of
acetone
for cleaning the circuits, and using silver (or even gold) solder...
others
have suggested measuring for resistance and figuring it from
there.... I get
the feeling low current designs seem to be more an art than a
science. Any
hints, pointers, or guffaws appreciated. Thanks

There are old instruments called 'electrometers' that are routinely
used
in this current range. The application notes associated with them
discuss lots of common problems and how to work around them. See for
example:

www.keithley.com/servlet/Data?id=6584

The usual techniques involve lots of cleaning, guarding (surrounding
the
measurement point with wires driven to the same potential), special
cables
such as triax, avoiding certain materials (watch out for the
photoelectric
effect!), control of humidity (if you can), and so on.

Lots of teflon!

I thought electrometers involved fairly high voltages.

One electron is 1.6x10^-19 coulombs, so 10^16 amps full scale is about
600 electrons/sec full scale. So your measurements will definitely be
noisy
and extreme care at controlling leakage will be required.

Lou Scheffer

 

[Robert Baer]

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Louis Scheffer" <lou@cadence.com> wrote in message
news:4162bb53$1@news.cadence.com...
"Greysky" <greyskynospam@sbcglobal.net> writes:

Anyone know of a reliable way of detecting currents less than one
femtoamp
i.e. 1X10^-16 amp full-scale? I figure to perhaps use some
instrumentation
amps air wired (no pc board) but have not had much luck getting
reliable
readings below about a nano amp - and at this scale, even an
accidental
breath can leave a film on the chip that creates a current path that
swamps
the signal I am looking for.... some have suggested using lots of
acetone
for cleaning the circuits, and using silver (or even gold) solder...
others
have suggested measuring for resistance and figuring it from
there.... I get
the feeling low current designs seem to be more an art than a
science. Any
hints, pointers, or guffaws appreciated. Thanks

There are old instruments called 'electrometers' that are routinely
used
in this current range. The application notes associated with them
discuss lots of common problems and how to work around them. See for
example:

www.keithley.com/servlet/Data?id=6584

The usual techniques involve lots of cleaning, guarding (surrounding
the
measurement point with wires driven to the same potential), special
cables
such as triax, avoiding certain materials (watch out for the
photoelectric
effect!), control of humidity (if you can), and so on.

Lots of teflon!

I thought electrometers involved fairly high voltages.

One electron is 1.6x10^-19 coulombs, so 10^16 amps full scale is about
600 electrons/sec full scale. So your measurements will definitely be
noisy
and extreme care at controlling leakage will be required.

Lou Scheffer

Err....Teflon is *NOT* good; see what Bob Pease has to say...
BTW, if the currents get *really* low,then use of Millikan's oil drop
experiment, or some reasonable equivalent - and *count* them!

 

[Watson A.Name - \"Watt Su]

"Tomi Holger Engdahl" <then@solarflare.cs.hut.fi> wrote in message
news:lajfz4vzjfr.fsf@solarflare.cs.hut.fi...

The web site at http://www.ethersplit.com/
describes an interresting technology ?

"etherSPLITtm employs a patent-pending system that splits 10BaseT
Ethernet and POTS (plain old telephone service) over four wires
(straight or twisted pair)."
"etherSPLITtm leverages all four wires in existing structures to
deliver 10BaseT (10 Mbps) Ethernet as well as one traditional POTS
line. The splitter system is enclosed in a simple wall-plate unit on
the user end that includes an RJ45 jack for Ethernet, and an RJ11 jack
for telephone. This unit, which replaces an existing telephone jack
plate, is connected through the building's existing copper wire to an
etherSPLITtm hub (or an etherSPLITtm interface unit that connects to
any standard 10BaseT hub.)"

Anyone tried tríed that technology ?

Has anyone seen what their adapter hve inside them.
Foer example their wall plate shown at
http://www.ethersplit.com/Pages/wallplatephoto.html
seem to be very simple.
What are those few components in it ?
And is the hub splitter more complicated ?

Appropriate newsgroups are comp.dcom.cabling, comp.dcom.ethernet,
comp.dcom.telecom.tech.

Probably just a balun, or something like the splitters used with DSL.

My thoughts are that no one will want to go back to 10 now that most
every PC has a 10/100/1000 NIC and most are running 100.

There already is DSL, and HPN. This technology will probably be as
successful as Token Ring.

Someday there will be fiber to the desktop, and copper won't be needed.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

 

[Rich Grise]

On Sunday 10 October 2004 01:48 am, Watson A.Name - "Watt Sun, the Dark
Remover" did deign to grace us with the following:

"Nicholas O. Lindan" <see@sig.com> wrote in message
news:TGy8d.4395$Vm1.3257@newsread3.news.atl.earthlink.net...
"Greysky" <greyskynospam@sbcglobal.net> wrote

Anyone know of a reliable way of detecting currents less than one
femtoamp
i.e. 1X10^-16 amp full-scale?

Look under 'electrometers'.

1 fA = 1e-15, ?. Are you looking for 0.1 fA FS?

1A = 6.2e18 electrons/second.
1fA = 6,200 electrons/second.

You are not looking at current, you are counting electrons/second.

Some engineer! No matter what the number of electrons, it's still a
current.

Yabbut, "current" kinda implies a smooth flow, like a river.
What they're talking about here would be much ... lumpier.

Thanks,
Rich

 

[Boris Mohar]

On Sun, 10 Oct 2004 01:44:06 -0700, "Watson A.Name - \"Watt Sun, the Dark
Remover\"" <NOSPAM@dslextreme.com> wrote:

"Greysky" <greyskynospam@sbcglobal.net> wrote in message
news:hjt8d.6675$nj.2550@newssvr13.news.prodigy.com...
Anyone know of a reliable way of detecting currents less than one
femtoamp
i.e. 1X10^-16 amp full-scale? I figure to perhaps use some
instrumentation

Let's see..
1 mA = 10^-3
1 uA = 10^-6
1 nA = 10^-9
1 pA = 10^-12
1 fA = 10^-15 _not_ 10^-16!

He said LESS than 1fA. 10^-16 is 100 attoamperes

It is doable with discrete front end of I/V op amp configuration. I used
3N155

--

Boris Mohar

 

[Winfield Hill]

Boris Mohar wrote...

He said LESS than 1fA. 10^-16 is 100 attoamperes

It is doable with discrete front end of I/V op amp
configuration. I used 3N155.

Tell us about your observed current offset and drifts.
(The 3n155 p-channel MOSFET is spec'd at 10pA maximum
gate leakage, for Vgs = -25V forward, admittedly a
rather silly and basically useless spec.)

Also, did you use any input protection circuitry?
What was the size of your feedback/sense resistor?
Where did you get it?


--
Thanks,
- Win

(email: use hill_at_rowland-dotties-org for now)

 

[CWatters]

"Dr. Slick" <radio913@aol.com> wrote in message
news:1d15af91.0410100716.1601b80@posting.google.com...

Good Evening,

I'm building a 12 volt recharging system with
a 12 volt, 0.375A (12"x12") solar cell, and this charge
controller:


http://store.dependablesolarproducts.com/etaen12vo5am.html


The battery is a 12 volt NiMH, 3AH.

Best check that charge controller is designed to work with NiMH cells. They
behave differently to Lead Acid cells.

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, that uses
3.6 volt NiMH, but i think there are Zener diodes that
limit the voltage coming from the generator to 7-8
volts, so i think i can remove these to get more
voltage (closer to 13-14 volts?).

Might work but I suspect you may have to turn the dynamo 3 or 4 times faster
(12/3.6 = 3.333 times). This might not be possible without changing the
gearing? At that voltage/rpm the dynamo may not be very efficient.

I other words, the charge controller (made for
photovoltaics) would be used for any of the three
sources of DC power.

You need to find out more info. Ask the makers if it's possible to power the
charge controller fro a DC source and what input voltage range is required
to charge 10 NiMH cells.

 

[James Meyer]

On 10 Oct 2004 08:16:11 -0700, radio913@aol.com (Dr. Slick) wroth:

Good Evening,

I'm building a 12 volt recharging system with
a 12 volt, 0.375A (12"x12") solar cell, and this charge
controller:


http://store.dependablesolarproducts.com/etaen12vo5am.html


The battery is a 12 volt NiMH, 3AH.

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains.

Slick

You don't need a charge controller for the solar cell source. Its
output is 1/10th of the battery's capacity and that amount of charge current
will be fine with no controller in the system.

You don't need a charge controller with the dynamo either.

If you use a "normal" commercial battery charger for the 120 volt AC
source, you won't need a seperate controller either.

A simple voltmeter will give you all the information you need to
determine the health of the battery.

Jim

 

[Bob Haberkost]

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com> wrote in
message news:10mi6qak441i47f@corp.supernews.com...

"mndflmr" <mndflmr@hotmail.com> wrote in message
news:n9j6m09u104h3rbod7ermst3jc421ltqon@4ax.com...

Recently I purchased a low-power VHF transmitter kit from Ramsey.
After building this kit, I have discovered that it will not work for
my purpose. I am trying to transmit audio and video about 20 feet from
a satellite receiver to my bedroom. The power output from the
transmitter is so low that the picture quality is very poor.

Here is the link to the kit manual:
http://www.ramseyelectronics.com/downloads/manuals/TV6.pdf

Ramsey purposefully left out the schematic page in this URL. Thanks for
nothing!

The circuit is simple enough that a schematic isn't all that necessary. At the same
time, I can see that there's very little that can be done to boost the signal, short
of adding components. This would be, if investigated by the FCC's enforcement of
unlicensed radiators (in excess of Part 15 regs) evidence that the user was in
violation of the "intentional radiator" limits under Part 15.

I would try better antennas before hacking the TV6.

The manual goes to some length to describe the expected coverage area for this
device. I'm with you that Joe has some issue with antennas (and again, please note
that putting an antenna with gain would suggest that the user is intentionally
violation Part 15). Is there a set-top antenna being used? Is the feedline from the
transmitter unit undamaged, and properly connected? Is there a balun being used to
match the 75-ohm output to a 300-ohm folded dipole?

BTW, you are shamefully crossposting to too many newsgroups!

I show the list of only 5 groups....not excessive, but more than I usually see
without it being tagged (and glommed) as spam.
--
-----------------------------------------------------------------------------
If there's nothing that offends you in your community, then you know you're not
living in a free society.
Kim Campbell - ex-Prime Minister of Canada - 2004
-----------------------------------------------------------------------------
For direct replies, take out the contents between the hyphens. -Really!-

 

[Joerg]

Hi Dr. Slick,

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, ...

Look into real alternators for motorcycles or cars. These are usually

much better quality and longer lasting. And cheap. Better bearings, too.

Regards, Joerg

http://www.analogconsultants.com

 

[James Meyer]

On Sun, 10 Oct 2004 20:24:57 GMT, "CWatters" <colin.watters@pandoraBOX.be>
wroth:

"James Meyer" <jmeyer@nowhere.net> wrote in message
news:e0oim05mg9j6vg55v23j0jpt5o4ovljtdb@4ax.com...

You don't need a charge controller for the solar cell source. Its
output is 1/10th of the battery's capacity and that amount of charge
current
will be fine with no controller in the system.

The 1/10th overcharge rate is usually ok (in that the battery won't over
heat or explode) but it might shorten the life of the battery if used long
term. Manufacturers recommend a lower rate if you are planning to leave the
battery on float for very long periods.

Solar cells will only provide current when the sun's shining. That
reduces the total current available over the long term to a value that should be
safe. Not to mention that most solar cell manufacturers rate their cells for a
perfectly clear day on top of Mt. Everest during a solar flare.

A simple voltmeter will give you all the information you need to
determine the health of the battery.

eg cells that exhibit a higher than normal "on charge" voltage are less
healthy.... or did you mean you can use a volt meter as a charge state
indicator? That's only possible if you calibrate it carefully

I meant that if one weren't going to automate the process or attempt to
provide legally binding measurements, that a quick look at the voltmeter would
provide all the information one should need to determine the condition of the
battery. Of course the voltage would be different depending on the load and the
temperature and whether the current was going into or out of the battery.

Jim

 

[m II]

James Meyer wrote:

Not to mention that most solar cell manufacturers rate their cells for a
perfectly clear day on top of Mt. Everest during a solar flare.

and when the planet is closest to the sun




mike

 

[Don Pearce]

On Mon, 11 Oct 2004 10:46:13 +0100, "Daniel Kelly \(AKA Jack\)"
<d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

Hi,

I have just built a PCB which holds a switched power supply and a microphone
amplifier. The power supply runs a camera whilst the audio amp is powered
directly from the 3.7v lithium polymer battery. The problem is that the amp
picks up a lot of noise from the powersupply. So much noise that the amp is
unusable at the moment. If I turn off the power supply then the amp runs
perfectly. Please could I ask your advice as to how best to limit this
noise? I've had a few ideas myself:

1) The PCB is doublesided and the back of the PCB is a ground plane. This
ground plane is continuous across the entire PCB so the powersupply and the
amp both share the same ground plane. If I separate the ground plane by
cutting the copper with a knife at the boundary between the two circuits,
will this limit some of the noise that's leaking from the power supply to
the amp?

2) Use better shielding on the PSU's inducer.

3) Build a separate PCB for the amp (something I don't really want to do
because I'm quite short of time).

Things I've tried already (but with no success):

1) Running separate power leads from the PSU and amp to the battery

2) Putting coupling capacitors all over the place.

3) Shorting the length of the microphone cable to the absolute minimum.

4) Shielding the entire PCB with grounded silver foil

5) Shielding only one circuit with grounded silver foil.

Thanks,
Jack

You need to revise this board radically, because you are trying to
make it do two things which are fundamentally incompatible - deal with
large, high voltage switching signals and tine signals from a
microphone.

First - as you suggest - slice across the ground plane so that the
amplifier and power supply are completely separated. Now link the
ground across to a single point, which should be the ground point for
the mic connector. You will still get some pickup until you have
attended to the grounding around the input, and that is a bit too
detailed to go into here, but get some references to star point
grounding in order to do this properly.

d
Pearce Consulting
http://www.pearce.uk.com

 

[Watson A.Name - \"Watt Su]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:2Thad.10712$nj.3362@newssvr13.news.prodigy.com...

Hi Dr. Slick,

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, ...

Look into real alternators for motorcycles or cars. These are usually
much better quality and longer lasting. And cheap. Better bearings,
too.

An alternator for an automobile, and probably a motorcycle also, are way
too much for a charger that needs only a half amp. Cars use a hundred
times that current.

I've used a hard disk spindle motor to drive some LEDs. Try it
sometime.
It depends on the motor, obviously it has to have permanent magnets.

Regards, Joerg

http://www.analogconsultants.com