Jury rigged powder measures

Discussion in 'Reloading' started by ADK_40GLKr, Oct 7, 2012.


  1. I may try one to try since they are inexpensive. I already have a good Dillon Eliminator to test it against.

    I do understand what some are saying. Just because the display reads down to .02 grain does not mean it is accurate to .02 grain. Kind of like an electronic caliper that displays down to .0005". It may have .0005" increments but nobody but a fool will depend on it below +-.002".
     

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    #41 dkf, Oct 8, 2012
    Last edited: Oct 8, 2012
  2. Why do you get so wound up about it? You reported about what the docs say exactly right. No one is doubting you. I've been using analog and digital scales for a long time and I simply don't buy their printed information as correct.

    Flash
     

  3. if nothing else its a handy backup or double/trlple check scale to have on hand. if you have any problems with yours please do share, I would be as interested as anyone since I do use mine quite regularly.
     
  4. Sorry, I am just pretty offended by SARDG's post and the way some have just assumed I have no idea what I am talking about. I try hard to be a positive, helpful presence on these boards. Reloading forums got me off to a good start in my reloading life and I am grateful for that and would like to return the favor.

    For the record, I have a BS in Mech Engineering and worked on some of the cooler toys in our national arsenal for one of the big defense contractors back in the day, I think I can run a little old scale;)
     
  5. From the manual, yes it does. Since it reads to 0.001 GRAM, reading to 0.02 GRAINS is not a problem. These are not typos, the numbers are straight out of the user manual.

    It would be interesting to see how it works against check weights.

    Richard
     
  6. They claim +- .02 grain accuracy and the norm is +- .1 grain (good) or +- .2 (fair). It could be a coincidence but it seems likely that there was an error.

    If I get a chance, I'll order the Gemini and try it. For the tiny cost, it would be worth buying if it's a reliable unit. I have several digital scales that didn't work well for powder charges but they still work great for weighing bullets or other components.

    For the record, I have a Masters in technology but once you get old and retire, folks think a lifetime of training and experience simply evaporates. I don't care if folks believe me or not.

    Flash
     
  7. Wow, I went away for a couple of hours and 25+ posts showed up before me.

    I am generally a fact-checker from way back, but it is so grossly uncommon for anything costing $22 to have an actual accuracy of .02gr that no checking was deemed necessary.

    However, the specs don't claim an accuracy of .02gr, they claim a resolution of .02gr. tkglazie, your original post claimed that the scale "measures to .02grains". Measures to (?), accuracy, resolution, and precision are all different animals. Take a look at this article, especially the Real-world Example at the bottom of the page that cuts to the chase:
    http://www.tutelman.com/golf/measure/precision.php

    The other parts of this page demonstrate how manufacturers hedge on precision and accuracy, by claiming good scores for resolution. Built in weighing algorithms may help perpetuate the illusion to the scale's end user. Repeatability and reliability are also mentioned regarding actual precision.

    I too would like to prove-up actual accuracy and real precision, and therefore repeatability and reliability in such an economical package - but fear it won't measure up (no actual pun intended).

    Of course, normal reloader's check-weights don't go down to .02gr, mine starting at .5gr.; so how we check the Gemini is unknown. There is another related page "Testing a Digital Scale" which seems to give correct procedures for accurate testing if you have the time and patience:
    http://www.tutelman.com/golf/measure/digitalScaleTest.php

    If I am found to be wrong, I most definitely would owe you an apology, but I am not yet convinced. My statement was actually made to convince ADK to choose wisely regarding which random posters to believe and I fear I was somewhat insensitive in the way I did that and apologize now for the insensitivity of my 'sell'.

    Kitty N.
     
  8. Well, for $25, I'll buy one & use it in my reloading class, the ammo is never shot, so I won't care. It certainly can't be worse than the $25 Hornady that never stays zeroed. I would expect a guy w/ a BS in engineering would know better. but hey, college isn't what it used to be. Check wts BTW, start @ 10grain & go down, not up. Check w/ certified check wts & get back to me. Weigh the same 10gr wt 10 x, it should never vary.
     
    #48 fredj338, Oct 9, 2012
    Last edited: Oct 9, 2012
  9. It may NOT vary during that test. The website article I referenced above claims that circuits built into cheaper scales can mask inconsistent measurements. If a 10gr weight is placed on the scale and actually measures 10gr, the circuits will take subsequent readings within a 'range' (as an example, 9.8-10.2gr) and display them as 10gr. The author suggests "cleansing the palette" of the scale between test weights by weighing a much heavier or lighter weight in between test weights.

    These algorithms are allegedly how low-cost scales can use resolution to mask inaccuracy and imprecision.
     
  10. I copied this from a conversion site:
    0.001g = 0.0154323580gr

    I copied this description of the Gemini 20 from an on line store:

    "Get quality and accuracy with the Gemini-20 digital gram scale. The Gemini-20 is accurate to 0.001 grams.

    So the scale is accurate to (rounding off) 0.02 grains
     
  11. What that specific online store has done is taken Gemini's "resolution" claim from the Gemini manual, and directly equated that to "accuracy", which we've determined are not the same.

    Manual (from Richard's link (Page 5):
    http://www.americanweigh.com/pdf/man...-20_manual.pdf
     
  12. Well, that guy sure paints a grim picture. I'm certain that there is some correlation between this and the link(s) I posted - just not sure I'm smart enough to figure out what it is.

    The scale addressed in this post is the Dillon and this same kind of conversion error isn't mentioned in the [my] former articles.
     

  13. He made a very basic mistake in that post. The D-Terminator is measuring to .003 gram NOT .01 grams as he seems to think. Look at the response from CED below.

    You need to be real careful reading this internet crap.
     
    #54 Colorado4Wheel, Oct 9, 2012
    Last edited: Oct 9, 2012

  14. That is a very interesting article! It is WRONG, but it is interesting.

    In the section "First response from me on Oct. 2, 2010:", there is a table that indicates that certain readings, in grains, aren't possible due to mathematical oddities related to rounding. For example, 4.7 grains should never show up on the scale. If the table is correct...

    So, how is it that I can walk out to the garage, load up a trickler and dispense a 4.7 gr charge? In fact, I watched for missing increments on the way up to 4.7 and, except for the occasions where I was overexuberant in twisting the knob, every single reading appears.

    There is certainly some technical basis for some of the author's ideas but the problem with 'facts' is that, sometimes, 'experiments' disprove them.

    I think that when a reloader moves from a quality beam scale to a digital scale, they have accepted the 0.05 gr error. I know that my Chargemaster and my D'Terminator don't agree to 0.1 gr. If I set the Chargemaster to dispense 42.2 gr, I will, more often than not, get 42.1 gr on the D'Terminator. I figure there are two round off errors going on and I'm willing to accept the variance.

    I use check weights in the range of interest. For a 42.2 gr charge, I use a 50.0 gr check weight. Both scales read EXACTLY 50.0 gr. That's great! But the engineer inside me also knows that I have no idea whether or not the check weight is anywhere near 50.0 gr. All I know is that three things tend to agree. They could all be wrong. But they would be wrong together!

    Another thing I learned: Your measuring device needs to resolve 10 times better than the thing you want to measure. If you want to measure 0.1 gr, you need to be able to resolve 0.01 gr, accurately. Which means that none of our common reloading measurements are worth a darn - engineering wise.

    But, darn, they seem to work anyway... Experiments...

    Richard
     
    #55 F106 Fan, Oct 9, 2012
    Last edited: Oct 9, 2012
  15. I think if I was CED I I would sue him and make him get rid of that slander.
     
  16. Because the article is wrong. The Scale measure to .003 grams which means it's accurate to .05 Grains (actually a little better) and then the scale rounds to .1 grains. So it has more resolution then it needs for it's given task. Not less as he falsely is asserting.
     
  17. Don't be surprised if you see a correction in that website in the near future.
     
  18. Exactly! As you pointed out, Internet stuff isn't always correct.

    Richard
     
  19. Yeah, so it says. Let's see, they are trying to sell you something and?????????
     

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