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Do Wiggle Stick Meters Wear Out?

Discussion in 'Electronic Repair' started by Watson A.Name - Watt Sun, Dark Remover, Dec 29, 2003.

  1. I bought a HP 721 PS on Ebay for thirty something incl S&H, does a
    whopping quarter amp at 30VDC, and uses all germanium devices, even
    the rectifiers, which are 1N91s I believe (they're not the original
    GEs, but they're marked SD 91, and are in the old top hat package). I
    put a PSO (phase shift oscillator) on it, which has its output driving
    a red LED. The freq is .38 Hz, or about a cycle every 2.5 seconds.
    So I get this 'fading red eyes' effect. Well, the little old wiggle
    stick meter on the PS goes from about a half mA on up to 9+ mA, back-
    and-forth, etc., along with the LED current.

    This old timer PS is probably from the mid '60s, 'cause I remember
    using one just like it back then. In fact, I've seen pictures of test
    setups from the late '50s with them in the picture. So it's got a
    lotta miles on it, but still going strong. The other day, there was
    one on Ebay, seller wanted $19.99 min bid, and nobody bid on it, the
    time just expired. I was watching the meter stick wiggle, and the
    thought occurred to me, maybe this meter has been in use for 30+
    years, but usually it's powered up and stays pretty much in one place.
    But I'm keeping it moving back and forth continuously. I'm wondering
    if these d'Arsonval meter movements ever wear out, or get gummed up.
    I think they're not lubricated so that shouldn't happen. But with
    jewels, what's the lifetime of the movement? A hundred thousand
    operations? A million? I'm curious, just wondering.


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  2. 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. :)

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

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

    --- 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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  3. Robert Baer

    Robert Baer Guest

    There are a lot of Weston meters still being used; mine was made in
    1947 and still going strong.
     
  4. How about the strength of the magnets? Old magnets may not maintain the
    same flux they started out with. Does that matter?

    Isaac
     
  5. Sam, you're a card. Heh. I hope I'll be around for a few more.
    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.
    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. 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. :-(


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  6. Asimov

    Asimov Guest

    "Isaac Wingfield" bravely wrote to "All" (29 Dec 03 05:30:49)
    --- on the heady topic of "Re: Do Wiggle Stick Meters Wear Out?"

    IW> From: Isaac Wingfield <>

    IW> In article <>,
    IW> How about the strength of the magnets? Old magnets may not maintain
    IW> the same flux they started out with. Does that matter?

    IW> Isaac

    That's not very likely. The old magnets would have had to be subjected
    to very high impacts or heat for them to weaken significantly. I've
    never heard of magnetic domains snapping out of alignment on their own
    but I haven't seen everything yet...

    .... No electrons were harmed in the posting of this message.
     
  7. 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.

    --- 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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  8. Jim Adney

    Jim Adney Guest

    If it's actually a jewelled movement then there is likely some finite,
    but large, lifetime. If it's a taut-band movement then I'd expect the
    lifetime to be virtually infinite.

    -
     
  9. Chuck Harris

    Chuck Harris Guest

    Consider that pocket watches use a very similar jeweled bearing on
    their balance wheel. The balance wheel rotates a few hundred degrees
    5 times per second. Pocket watches are typically serviced every other
    year. They last for hundreds of years.... and yes, unlike a meter,
    they are oiled.

    Your meter rotates a maximum of 60 degrees, typically. It would have
    to go zero to full scale 5 times per second to get even close to a
    pocket watch's bearing activity.

    -Chuck Harris
     
  10. DarkMatter

    DarkMatter Guest

    Unless they were heated or affected by a demagnitizer operating
    nearby... why would they?
     
  11. DarkMatter

    DarkMatter Guest

    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

    D'arsonval utilizes magnetism, and taut band utilizes thermal
    expansion constants. The taut band is more accurate as it is directly
    attached to the needle. Magnetism is a bit more spongy, and therefore
    can exhibit error prone operation, with less linearity through its
    range. The taut band is repeatable through years of service (with
    calibration), and being directly attached to the needle, has near zero
    error through it's range, and a higher degree of linearity precision.
     
  12. Guest

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

    Thanks
    George
     
  13. Hey, thanks, I never thought about comparing the meter movement to a
    balance wheel in a clock/watch. But then ever since the late '60s
    I've been using watches that don't have a balance wheel. ;-)

    I found a digital watch movement out on the street the other day. Bit
    rusted from the rain. I'll have to take the batt out and see if it
    will still work.
     
  14. Sapphire or ruby? I forget. Here's a FAQ I found:
    http://www.oris.ch/english/faq.htm
    Skip down to the paragraph 4th from the bottom.


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    Subject: line with other stuff. alondra101 <at> hotmail.com
    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
    @@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
     
  15. HAH! ROTFL! Read the second from the bottom paragraph! Those Swiss
    elves don't know the diff between lubricate and duplicate! :)

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    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    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
    @@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
     
  16. Chuck Harris

    Chuck Harris Guest

    That is incorrect!

    The taut-band is a frictionless suspension system for the coil
    in the meter.

    The biggest advantage of a taut-band suspension over a jeweled bearing
    suspension is this lack of friction.... You can make a more sensitive
    meter movement with the taut-band system.
    Do a google search on "taut band meter" You will find pictures and
    descriptions-a-plenty.

    -Chuck Harris
     
  17. 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.

    --- 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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  18. 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.

    These are both D'Arsonval - coil in magnetif field - movements.

    There are also other types of meters but the references in this thread
    all refer to these types.

    --- 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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  19. DarkMatter

    DarkMatter Guest

    When one has a shaft that needs to be able to turn very freely, and
    said shaft is so small that normal bearing of the type used on bigger
    shafts wont work, a small cup shaped bearing, made from a hard
    crystalline material has a long life, high precision, and the pin ends
    of the shaft do not have a high degree of friction on them.

    A shaft placed on a metal hole would wear, and wobble badly after a
    short period of action, and would also likely bind in operation.

    Jeweled bearings on small shafts like instrumentation or watches and
    clocks makes for years of dependable maintenance free service for the
    shaft.

    A jeweled bearing can last hundreds of years. The only thing that
    will or can wear is the shaft pin end itself, as the bearing is of a
    much harder media.
     
  20. DarkMatter

    DarkMatter Guest

    I know what a jeweled bearing is.
     
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