Calibrating a calibrator?

Discussion in 'Stringing Techniques / Stringing Machines' started by beernutz, Jul 6, 2009.

  1. beernutz

    beernutz Hall of Fame

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    So I went and bought a new Berkley digital fish scale at Walmart to calibrate my new (to me) Neos 1000 because I read on the forum that the scales were cheap at under $20 and also reasonably accurate.

    The Neos, when set to 50 pounds tension, initially measured at 49.9 then quickly would drop off a couple of pounds. I presume this drop off was due to the synthetic gut I was using to attach the fish scale to the Neos stretching. I figured that the initial .1 pound difference was close enough for government work so I didn't try to change any settings on the Neos.

    However, just for grins I thought I'd hook (rolls eyes) the fish scale up to my old Klippermate and measure its tension when it was set to 50 pounds. I was somewhat surprised when the Klippermate measured 47.3 pounds when the bar was perfectly horizontal and I assume this discrepancy was due to the measuring tape on the Klippermate being attached incorrectly.

    Anyway, I am thinking now that I'd better calibrate the fish scale with something to make sure it is not the problem. I have some freeweights in my house I could use but I'm not positive that their weights are accurate. Would a postal scale be a good place to measure something that I could then use to check the accuracy of the digital fish scale? Any other suggestions for calibrating a calibrator?
     
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  2. diredesire

    diredesire Super Moderator

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    The drop off WAS due to the string relaxing. If you have any scrap kevlar, that might help you get a "true-er" reading.

    The only reliable way to calibrate is to use a known, standard(ized) weight. These can cost a lot in the weights you're looking for, so the cheapest way would be to use something like a postal scale to measure. You can take some stuff into the post office (like a backpack weighted with crap) and ask them to weigh it for you, their scales are calibrated regularly (from what I understand). They have stand-alone scales in some Post Offices, but they'll generally only weigh up to a pretty low limit (15 lbs mayyybe?)

    My suggestion: Bring a backpack, weigh your backpack, sequentially weigh, then add your free weights, and calculate something close to 50-60 lbs, and then use that to calibrate. Make sure your scale is tied to something rock solid, and try to use a stiffer string.
     
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  3. beernutz

    beernutz Hall of Fame

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    Thanks that is helpful. I don't have any kevlar but I have some scrap poly string (lux alu) which I don't think stretches very much which I'll use.
     
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  4. diredesire

    diredesire Super Moderator

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    It's likely that you will see a bit of a tension drop regardless of whatever scrap you decide to use. Just keep an eye peeled for the point at which the tensioner locks out.
     
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