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)
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!!
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)
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:
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I'm hoping to forget the term but probably never will. :)
--- sam | Sci.Electronics.Repair FAQ Home Page:
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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 snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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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 snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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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 snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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In article , tony snipped-for-privacy@tpg.com.au mentioned...
It's just one of those terms, like fire bottles.
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I read in alt.binaries.schematics.electronic that Sam Goldwasser wrote (in ) about 'Do Wiggle Stick Meters Wear Out?', on Tue, 30 Dec 2003:
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!
I read in alt.binaries.schematics.electronic that Tweetldee wrote (in ) about 'Do Wiggle Stick Meters Wear Out?', on Tue,
30 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.
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!
I read in alt.binaries.schematics.electronic that Jim Adney wrote (in ) about 'Do Wiggle Stick Meters Wear Out?', on Tue, 30 Dec 2003:
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!
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.
to
I read in alt.binaries.schematics.electronic that BFoelsch wrote (in ) about 'Do Wiggle Stick Meters Wear Out?', on Wed, 31 Dec 2003:
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!
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
I read in alt.binaries.schematics.electronic that Chuck Harris wrote (in ) about 'Do Wiggle Stick Meters Wear Out?', on Wed, 31 Dec 2003:
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!
On Wed, 31 Dec 2003 12:38:03 -0500, "BFoelsch" Gave us:
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.
On Wed, 31 Dec 2003 14:35:31 -0500, Chuck Harris Gave us:
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:
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
I read in alt.binaries.schematics.electronic that Chuck Harris wrote (in ) about 'Do Wiggle Stick Meters Wear Out?', on Wed, 31 Dec 2003:
Not really; you are on the right lines insofar as a low value of L/C make oscillation less likely, as I show below. But you haven't actually mentioned the key word. The crucial factor is the *resistance* of the coil, as I tried to indicate before. If R =>sqrt(L/C) the current won't oscillate. It didn't.
-- 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!
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