Do Wiggle Stick Meters Wear Out?

[DarkMatter]

On Tue, 30 Dec 2003 08:16:02 -0500, Chuck Harris <cfharris@erols.com>
Gave us:

DarkMatter wrote:

The difference between d'arsonval and taut band is the actuation of
the needle, not the support bearing(s). Any mechanical meter movement
that I know of has jeweled bearings, taut band or otherwise

That is incorrect!

Yes. Thank you. I was taught that they were a different actuation
method than D'Arsonval. I didn't realize that they were both
d'arsonval, but that the taut band was a suspension system. I thought
it was the actuation method.

 

[John Stewart]

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

In article <6w4qvkjonv.fsf@saul.cis.upenn.edu>, sam@saul.cis.upenn.edu
mentioned...
Older meters use jeweled movements and yes they probably do wear
out. I've never seen one fail due to worn bearings. Usually
it is from mechanical or electrical abuse.

We are all on the edge of our seats awaiting your report.
I expect it will be a few years or decades though.

Sam, you're a card. Heh. I hope I'll be around for a few more.

Higher quality meters may taut band suspensions which shouldn't wear
out, at least not in the same way.

I hada high school friend who had a Simpson taut band meter. It
wasn't a 260, but a bigger meter where the meter movement itself was
most of the case. I think the movement was 20 uA, it was really low
current. Slow to move, but it had a mirror behind the needle.

I suppose that if this will keep you from sleeping at night, you could
install a switch to disable the meter. ;-)

Yeah, the range can be changed to higher curent or voltage where the
stick doesn't wiggle at all as long as I keep my fingers off the V
control. Funny, but these old PSes were built like tanks: they have
an aluminum chassis inside an aluminum case.

The HP 700 Series were actually built by a division of HP in Palo Alto.
Around the early 60's, HP bought Harrison Labs in NJ, so all the PS's
from then on came from that facility. HP built there own transfomers
for other applications in Palo Alto.

Cheers, John Stewart (ex-HP Sales)

Then later HP made the
6214A and 6216A PSes and the cases are so fragile and brittle that
they crumble when you try to take them apart. :-(

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
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[Tweetldee]

"Sam Goldwasser" <sam@saul.cis.upenn.edu> wrote in message
news:6w3cb3vfvh.fsf@saul.cis.upenn.edu...

Isaac Wingfield <isw@witzend.com> writes:

In article <6w4qvkjonv.fsf@saul.cis.upenn.edu>,
Sam Goldwasser <sam@saul.cis.upenn.edu> wrote:

Older meters use jeweled movements and yes they probably do wear
out. I've never seen one fail due to worn bearings. Usually
it is from mechanical or electrical abuse.

How about the strength of the magnets? Old magnets may not maintain the
same flux they started out with. Does that matter?

Yes, it does matter. They are probably ALNICO magnest but used with
a very low exciting field (the current through the coil) so they probably
don't loose much of their strenght over time.

Good thought though.

When I worked in a calibration lab (late 60's-early 70's), we had an
instrument called a "Magnetreater", made by RFL I think. It was used to
fine-tune the strength of the magnet in a D'Arsonval movement. The lab was
a calibration, warranty repair and customization center for Simpson, Weston,
and API meters. We even had a drafter that could draw custom scales for the
meters.
We could adjust a meter movement to have +/- 1/4% FS accuracy with the
Magnetreater. It operated similarly to a CD Ignition system, in that a
charge stored in a large capacitor bank was dumped into a coil. The meter
being treated was placed inside the coil. By sending a calibrated current
through the meter, you could watch the meter sensivity change with each
pulse of the treater. Interesting to watch...

I'd like to have one of those, just to experiment and have fun with magnets
and magnetism. I've seen a couple listings on the net from Tucker and
Used-Line, but they want like-new prices for them. I've been watching Ebay,
but so far, nothing that resembles a magnetreater has shown up. Does anyone
happen to have one of these guys stored away under the workbench in your
garage? If so, can we talk?
Thanks,
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!

 

[Tony Roe]

I just had to read this thread to find out what a "wiggle stick meter" was, and
thus increase my vocabulary.

Tony (remove the "_" to reply by email)

 

[Sam Goldwasser]

"Tweetldee" <dgmason99@att99.net> writes:

When I worked in a calibration lab (late 60's-early 70's), we had an
instrument called a "Magnetreater", made by RFL I think. It was used to
fine-tune the strength of the magnet in a D'Arsonval movement. The lab was
a calibration, warranty repair and customization center for Simpson, Weston,
and API meters. We even had a drafter that could draw custom scales for the
meters.

We could adjust a meter movement to have +/- 1/4% FS accuracy with the
Magnetreater. It operated similarly to a CD Ignition system, in that a
charge stored in a large capacitor bank was dumped into a coil. The meter
being treated was placed inside the coil. By sending a calibrated current
through the meter, you could watch the meter sensivity change with each
pulse of the treater. Interesting to watch...

I'd like to have one of those, just to experiment and have fun with magnets
and magnetism. I've seen a couple listings on the net from Tucker and
Used-Line, but they want like-new prices for them. I've been watching Ebay,
but so far, nothing that resembles a magnetreater has shown up. Does anyone
happen to have one of these guys stored away under the workbench in your
garage? If so, can we talk?

That is really intersting. I bet you could make one of those fairly easily.

It does just produce a high current pulse in a coil.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.

 

[Sam Goldwasser]

Tony Roe <tony_roe@tpg.com.au> writes:

I just had to read this thread to find out what a "wiggle stick meter" was,
and thus increase my vocabulary.

I'm hoping to forget the term but probably never will.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.

 

[Jim Adney]

On Mon, 29 Dec 2003 05:30:49 GMT Isaac Wingfield <isw@witzend.com>
wrote:

In article <6w4qvkjonv.fsf@saul.cis.upenn.edu>,
Sam Goldwasser <sam@saul.cis.upenn.edu> wrote:

Older meters use jeweled movements and yes they probably do wear
out. I've never seen one fail due to worn bearings. Usually
it is from mechanical or electrical abuse.

How about the strength of the magnets? Old magnets may not maintain the
same flux they started out with. Does that matter?

The field strength of magnets really doesn't change at all unless you
do something to change it. This would require either that you bring
some large piece of iron into the field, or that you impose a very
large magnetic field on the magnet. Neither of these is likely within
a meter movement under normal circumstances.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Jim Adney]

On 30 Dec 2003 08:18:45 -0500 Sam Goldwasser <sam@saul.cis.upenn.edu>
wrote:

george@myfarm.com writes:

What exactly does using jewels mean? Obviously they use some sort of
diamond or other "rock", but where and how?
I never understood this ????

The shaft on which the meter coil is mounted has points at either end
that rotate within a conical cavity in ruby or other similar hard material.

It is exactly the same as the "jewels" in a watch movement. They are
usually little sapphire beads with a conical hole in them which serves
as the bearing for a small shaft. The jewel is pressed into a metal
part which supports it.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Jim Adney]

On 30 Dec 2003 08:22:55 -0500 Sam Goldwasser <sam@saul.cis.upenn.edu>
wrote:

DarkMatter <DarkMatter@thebarattheendoftheuniverse.org> writes:

The difference between d'arsonval and taut band is the actuation of
the needle, not the support bearing(s). Any mechanical meter movement
that I know of has jeweled bearings, taut band or otherwise

No. It specifically deals with the bearings. Jeweled bearings have
a steel shaft pointed at both ends rotating within a concave cavity in a
ruby or other similar hard bearing material.

A taut band movement suspends the coil and needle on a very thing
tensioned steel band which both provides the electrical connections
and restoring force. There is no static friction with such a device.

Sam's right.

There are (at least) two kinds of meter movement bearings: jewelled
and taut band.

There are (at least) two kinds of electromagnetic schemes for creating
the meter motion: d'Arsonval (moving coil) and moving magnet.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Watson A.Name - "Watt Sun]

In article <vus3vv0kr5ajipnibrtmb8j2bop6kj486h@4ax.com>,
tony_roe@tpg.com.au mentioned...

I just had to read this thread to find out what a "wiggle stick meter" was, and
thus increase my vocabulary.

Tony (remove the "_" to reply by email)

It's just one of those terms, like fire bottles.



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Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[John Woodgate]

I read in alt.binaries.schematics.electronic that Sam Goldwasser
<sam@saul.cis.upenn.edu> wrote (in <6wwu8efnio.fsf@saul.cis.upenn.edu&gt
about 'Do Wiggle Stick Meters Wear Out?', on Tue, 30 Dec 2003:

A taut band movement suspends the coil and needle on a very thing
tensioned steel band which both provides the electrical connections
and restoring force.

I was given a classic Cambridge galvanometer with a broken taut-band
suspension. The original band was phosphor bronze, not steel. I replaced
it with 3 mil stainless steel wire (yes, from a wire recorder from the
same source as the galvo!). It was about 10 times less sensitive.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[John Woodgate]

I read in alt.binaries.schematics.electronic that Tweetldee
<dgmason99@att99.net> wrote (in <02lIb.259370$Ec1.8964982@bgtnsc05-news.
ops.worldnet.att.net&gt about 'Do Wiggle Stick Meters Wear Out?', on Tue,
30 Dec 2003:

I've been watching Ebay,
but so far, nothing that resembles a magnetreater has shown up. Does anyone
happen to have one of these guys stored away under the workbench in your
garage? If so, can we talk?

I made one many years ago, admittedly with some help with the mechanical
engineering. For the coil, I used a 'no volt coil' from a motor starter
but a mains transformer primary winding works, if you can get the
transformer apart. A half-wave rectifier charged a 50 uF 400 V capacitor
(electrolytic) from the mains (240 V then) through a 10 kohm resistor
(no hurry to charge up! and the delay allows the coil to cool down). A
simple push-button switch then connected the capacitor to the coil. The
current starts at zero, because of the inductance, and ends at nearly
zero, because it's just the current through the 10 kohms. But in
between, it's BIGGER, just limited by the d.c. resistance of the coil.
IIRC, it gave 4 A through 2000 turns.

This was for magnetizing the motor magnets of model trains, and the
model maker made the core and clamping arrangement from a grade of
Swedish iron, but a very low carbon steel would probably do. If you can
take a transformer to pieces, you may be able to modify the core
laminations to make a suitable core for the magnetizer. But the silicon
iron is very hard on tools, even on shears.

The commercial magnetizers seem to use far more 'heroic' techniques,
resulting in 'boat anchor' equipment. But for big magnets, obviously you
need a big magnetizer.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[John Woodgate]

I read in alt.binaries.schematics.electronic that Jim Adney
<jadney@vwtype3.org> wrote (in <b802vv0bea131dmodpmei3vc9167nk44g4@4ax.c
om&gt about 'Do Wiggle Stick Meters Wear Out?', on Tue, 30 Dec 2003:

The field strength of magnets really doesn't change at all unless you
do something to change it. This would require either that you bring
some large piece of iron into the field, or that you impose a very
large magnetic field on the magnet. Neither of these is likely within
a meter movement under normal circumstances.

This is true if they have been 'stabilized' after initial magnetizing,

which leaves the material at an unstable point on the BH loop. You apply
a small reverse field to bring the state to a stable point, otherwise
any small vibration causes the strength to drop.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[BFoelsch]

OK - related question.

In a past life I frequently worked on small devices with small magnets. The
specific manufacturer with whom I worked preached long and loud about NOT
breaking the magnetic circuit during disassembly, putting keepers on before
disassembly, and the need to remagnetize after re-assembly. I am talking
about 1950 era magnets here.

How much truth is there to this concern. Was it valid in 1950?

Equipment in question was audio recording devices; cutter heads, pickups,
microphones, etc.

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:0z$oK0HZPw8$EwA4@jmwa.demon.co.uk...

I read in alt.binaries.schematics.electronic that Jim Adney
jadney@vwtype3.org> wrote (in <b802vv0bea131dmodpmei3vc9167nk44g4@4ax.c
om&gt about 'Do Wiggle Stick Meters Wear Out?', on Tue, 30 Dec 2003:

The field strength of magnets really doesn't change at all unless you
do something to change it. This would require either that you bring
some large piece of iron into the field, or that you impose a very
large magnetic field on the magnet. Neither of these is likely within
a meter movement under normal circumstances.

This is true if they have been 'stabilized' after initial magnetizing,
which leaves the material at an unstable point on the BH loop. You apply
a small reverse field to bring the state to a stable point, otherwise
any small vibration causes the strength to drop.
--
Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go
to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[John Woodgate]

I read in alt.binaries.schematics.electronic that BFoelsch
<BFoelsch@snet.ditch.this.net> wrote (in <ppmdnfbD2IbnlG6i4p2dnA@giganew
s.com&gt about 'Do Wiggle Stick Meters Wear Out?', on Wed, 31 Dec 2003:

In a past life I frequently worked on small devices with small magnets. The
specific manufacturer with whom I worked preached long and loud about NOT
breaking the magnetic circuit during disassembly, putting keepers on before
disassembly, and the need to remagnetize after re-assembly. I am talking
about 1950 era magnets here.

How much truth is there to this concern. Was it valid in 1950?

It's still valid for some materials. It depends on the coercivity.
Ferrite magnets usually have such a huge coercivity that it isn't
necessary to keeper them.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[Chuck Harris]

John Woodgate wrote:

I read in alt.binaries.schematics.electronic that Tweetldee
dgmason99@att99.net> wrote (in <02lIb.259370$Ec1.8964982@bgtnsc05-news.
ops.worldnet.att.net&gt about 'Do Wiggle Stick Meters Wear Out?', on Tue,
30 Dec 2003:

I've been watching Ebay,
but so far, nothing that resembles a magnetreater has shown up. Does anyone
happen to have one of these guys stored away under the workbench in your
garage? If so, can we talk?


I made one many years ago, admittedly with some help with the mechanical
engineering. For the coil, I used a 'no volt coil' from a motor starter
but a mains transformer primary winding works, if you can get the
transformer apart. A half-wave rectifier charged a 50 uF 400 V capacitor
(electrolytic) from the mains (240 V then) through a 10 kohm resistor
(no hurry to charge up! and the delay allows the coil to cool down). A
simple push-button switch then connected the capacitor to the coil. The
current starts at zero, because of the inductance, and ends at nearly
zero, because it's just the current through the 10 kohms. But in
between, it's BIGGER, just limited by the d.c. resistance of the coil.
IIRC, it gave 4 A through 2000 turns.

What you describe is a *demagnetizer*. Here's why, when you start with
the cap charged up, all of the charge goes into the inductor and charges
up the inductor, the inductor returns the favor and returns the current
to charge the cap, and back and forth the current travels thru the
coil. Eventually it dies down to zero because a little is lost each
time due to resistance, and core/magnetic losses.

This is the classic "instantaneous" demagnetizer used by watchmakers
to demagnetize watch parts.

To turn it into a *magnetizer* you need a way to prevent the energy
transfer from the coil back into the capacitor. That would be a
diode in series with the capacitor.

-Chuck Harris

 

[John Woodgate]

I read in alt.binaries.schematics.electronic that Chuck Harris
<cfharris@erols.com> wrote (in <3ff32503$0$4742$61fed72c@news.rcn.com&gt
about 'Do Wiggle Stick Meters Wear Out?', on Wed, 31 Dec 2003:

I made one many years ago, admittedly with some help with the mechanical
engineering. For the coil, I used a 'no volt coil' from a motor starter
but a mains transformer primary winding works, if you can get the
transformer apart. A half-wave rectifier charged a 50 uF 400 V capacitor
(electrolytic) from the mains (240 V then) through a 10 kohm resistor
(no hurry to charge up! and the delay allows the coil to cool down). A
simple push-button switch then connected the capacitor to the coil. The
current starts at zero, because of the inductance, and ends at nearly
zero, because it's just the current through the 10 kohms. But in
between, it's BIGGER, just limited by the d.c. resistance of the coil.
IIRC, it gave 4 A through 2000 turns.

What you describe is a *demagnetizer*. Here's why, when you start with
the cap charged up, all of the charge goes into the inductor and charges
up the inductor, the inductor returns the favor and returns the current
to charge the cap, and back and forth the current travels thru the
coil. Eventually it dies down to zero because a little is lost each
time due to resistance, and core/magnetic losses.

This is the classic "instantaneous" demagnetizer used by watchmakers
to demagnetize watch parts.

To turn it into a *magnetizer* you need a way to prevent the energy
transfer from the coil back into the capacitor. That would be a
diode in series with the capacitor.

How astonishing then that the thing worked, and worked extremely well.
Of course, IF the coil had been made out of superconductor, the circuit
would have oscillated, but it was just plain ordinary copper so it
didn't oscillate and simply worked.

Do you think I would have posted about it if it didn't work?

If there had been a Mark 2 model, this would have had the capacitor
value chosen so as to make the transient response slightly underdamped,
so that the small reverse induction stabilised the working point of the
magnet. For the model train application it wasn't necessary.

To measure the effectiveness of the magnetizer, we set up a straight
inclined track and had the locos pull passenger carriages up it. The
original motor was good for 10, a newly magnetized motor would just do
14, and after a day or two it would do 12 or 13, as the working point
stabilized. The 14 is an underestimate, because the power supply voltage
drooped to 11 V with all that load.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[DarkMatter]

On Wed, 31 Dec 2003 12:38:03 -0500, "BFoelsch"
<BFoelsch@snet.ditch.this.net> Gave us:

OK - related question.

In a past life I frequently worked on small devices with small magnets. The
specific manufacturer with whom I worked preached long and loud about NOT
breaking the magnetic circuit during disassembly, putting keepers on before
disassembly, and the need to remagnetize after re-assembly. I am talking
about 1950 era magnets here.

How much truth is there to this concern. Was it valid in 1950?

Equipment in question was audio recording devices; cutter heads, pickups,
microphones, etc.

AlNiCo was a big choice in magnets back then, but there were still
weaker alloys in use.

I suppose such alloys had poorer "retentivity", and could be prone
to losses in open ended situations.

I did find an excellent learning resource on it, however.

http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/Quantifying.htm

 

[DarkMatter]

On Wed, 31 Dec 2003 14:35:31 -0500, Chuck Harris <cfharris@erols.com>
Gave us:

To turn it into a *magnetizer* you need a way to prevent the energy
transfer from the coil back into the capacitor. That would be a
diode in series with the capacitor.

Or a static dc source, but then, one needs to physically move the
standing field over the target medium.

This is the same as natural magnetizing. A static magnet must be
passed along the length of the target medium without making actual
contact.

If one merely places it near the standing field, it merely
influences, then releases. For such a coil to work, it would have to
be set up with a standing field by way of a hard DC source, not a
depleting one (that actually reciprocates) such as a cap bank.

So... a non-inverting field is needed, and MOTION is also needed to
"comb" the atoms into alignment, and then they begin to retain it.

Coercivity is not only how easily one can change the alignment
set of a medium, but also how easily that medium can lose it.

Retentivity is how much remains after the magnetizing influence has
been removed. This site explains it much more thoroughly than I can:

http://www.ndt-ed.org/EducationResources/CommunityCollege/MagParticle/Physics/Quantifying.htm

 

[Chuck Harris]

John Woodgate wrote:

What you describe is a *demagnetizer*. Here's why, when you start with
the cap charged up, all of the charge goes into the inductor and charges
up the inductor, the inductor returns the favor and returns the current
to charge the cap, and back and forth the current travels thru the
coil. Eventually it dies down to zero because a little is lost each
time due to resistance, and core/magnetic losses.

This is the classic "instantaneous" demagnetizer used by watchmakers
to demagnetize watch parts.

To turn it into a *magnetizer* you need a way to prevent the energy
transfer from the coil back into the capacitor. That would be a
diode in series with the capacitor.


How astonishing then that the thing worked, and worked extremely well.
Of course, IF the coil had been made out of superconductor, the circuit
would have oscillated, but it was just plain ordinary copper so it
didn't oscillate and simply worked.

Do you think I would have posted about it if it didn't work?

What you are describing is also called a tank circuit, or a parallel
resonant L-C circuit.

When I first ran across one, it was in an L&R watch demagnetizer.
I thought as you do that it would magnetize the material... But it
didn't. It demagnetizes the material in a blink of the eye. I used
one almost daily in repairing watches.

I would guess that the difference has something to do with how big
your capacitor is, vs how big the coil is. Perhaps if the coil is
really small in inductance, and the capacitor is very large in
capacitance you get enough loss that the coil cannot pass the energy
back to the capacitor before it is mostly all gone?

-Chuck Harris

If there had been a Mark 2 model, this would have had the capacitor
value chosen so as to make the transient response slightly underdamped,
so that the small reverse induction stabilised the working point of the
magnet. For the model train application it wasn't necessary.

To measure the effectiveness of the magnetizer, we set up a straight
inclined track and had the locos pull passenger carriages up it. The
original motor was good for 10, a newly magnetized motor would just do
14, and after a day or two it would do 12 or 13, as the working point
stabilized. The 14 is an underestimate, because the power supply voltage
drooped to 11 V with all that load.