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  1. #1

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    Luna Pro battery adapter $$$$

    Why do these cost so much -$60@B&H? They're just a small metal sleeve w/a bump in them.
    Last edited by chip j; 02-09-2014 at 11:22 PM. Click to view previous post history.

  2. #2

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    If they are voltage regulators designed to use the 3v silver battery combos and regulate it to 2.7v, then the silver battery's ability to give flat response (output) over its lifespan; is enhanced to approach or rival mercury batteries. I'm not sure what they are--just heard of them. But if what I believe is so, then it is the best 60 you'll ever spend. If you have a luna-pro with its cell still running linear, then you have the best meter ever made.
    A few years ago I researched this subject exhaustively. I found a man who actually had designed and had some prototype regulators made to his order. I bought one of the remaining prototypes after he got married and his priorities changed, and abandon the project. I wired in my little regulator into my luna-pro's power supply circuit, and it has performed beautifully. You get accurate readings till the batteries' last gasp of breath, then dies. Flat as a pancake is the resonse till that last gasp.
    Or you can tinker around with hairbrain schemes and never have an accurate meter for more than a few days till the voltage curve changes. BTDT

  3. #3

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    The battery adapter isn't a regulator, just a precise voltage drop and form factor fix for silver oxide battery replacements. Silver oxide batteries have the same lifespan property of mercury, their voltage doesn't drop until the end and so the regulation isn't needed.

    The cost comes from this: "high volume low cost or low volume high cost, pick one" It's a niche item with some tiny electronic bits and it's still cheaper than sending a Luna Pro out to the one or two shops that can modify the guts inside the case directly.

  4. #4

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    I think you need to further study the voltage curves. Silvers are not flat but for their first 50% of their lifespan. From that point they become no better than alkalines. But the subject is now moot with your information that they are not true regulators. The prototype I bought was a true regulator, even with the ability to raise voltage when the 2.7v fall-off point had been reached. At least, within a reasonable timespan. But by then, the actual battery curve was so far along as to be near depletion, anyway.

  5. #5

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    Modify the guts? Well, heck, I can do that with 2 shakes of a lambs tail. What's that going to do for the lousy curve of most batteries? Like I said--BTDT.

  6. #6

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  7. #7

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    Quote Originally Posted by Tom1956 View Post
    Awesome, thanks! I'll keep my batteries on a shortened replacement schedule now.

    Eventually I'll replace my old Luna Pro that I've had since HS in the late 70's, but for now this is how I've kept it running.

  8. #8

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    Sure, friend. But there's no reason to replace it. Keep an eye on lower end response for accuracy. That assured, your CdS cell linearity is still good and there's no reason to get rid of it.

  9. #9
    AgX
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    Do it yourself, with the manual by de Gruijter:

    http://www.buhla.de/Foto/batt-adapt-US.pdf

  10. #10

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    google battery cell problem and as well try this link...
    http://rick_oleson.tripod.com/index-111.html
    but silver cells are close enough?

    if you use the meter every day use a Zn air cell if infrequent use a silver cell and diode replace every 18m.

    for an accurate light meter I use a Weston II or III

    the local village electical shop still sells Shockety diodes (Maplins).

    oops AgX posted the other link

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