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Author: Subject: Some advice on 20g range scales needed
Gargamel
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[*] posted on 1-5-2018 at 02:04
Some advice on 20g range scales needed


Perhaps you can give me some advice or even suggest something.

To make it short, I'm looking for a proper scale to measure out very small amounts, not overstraining my limited budget (A contradiction, I know...).
Im just a guy that does some small scale experimentation at home, A "real" lab scale is out of question. Lets just say I'd like to spend 100€ or so.


A typical task would be 100mg with an accuracy of 10%.
Do you think that is a feasible task for that money?


There are many scales with 0,001g read-out on the market, but usually the vendors give little information about accuracy.
Im looking for something like so-and-so much percent + so-and-so much digits - in vain.





Two things that are also important for me:
No auto power off! At least not within 2 or better 5 minutes or so.


And ideally, the scale should be able to dose something. You know, one crumble, another one, another one...
And the scale wont move, because it tries to stabilize its zero position...
-> the measurement is ruined.
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yobbo II
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[*] posted on 1-5-2018 at 09:14


...."And ideally, the scale should be able to dose something. You know, one crumble, another one, another one.."...

No, I don't know!

Yob
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wg48
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[*] posted on 1-5-2018 at 13:01


Its frustrating that most scales do not specify the absolute accuracy even if the cost is more than £100. I am ignoring the ads that claim the resolution is the accuracy.

Have thought about it, it probably because g can change by about 0.1% from place to place. So its expected that the scales will be calibrated with a know mass so the reproducibility and linearity are specified only.

If your only after 10% at 30g (that’s+/-3g) accuracy its probably hard to find electronic scales that are not that accurate provided the resolution is at least 0.03g and the cost will be a lot less that 100euro. Sooner or later you will want to measure something in a flask or beaker so I suggest to go for a max of say 250g with a resolution of at least 0.1g and even a resolution of 10mg will cost you less than 100euro.

If your still worried about accuracy you can purchase calibration weights for about £12 with a claimed accuracy of +/-10mg (if you believe it) from ebay. Unbelievable I found most ads for calibration weights did not specify the accuracy, how crazy is that.

However the UK Mint quotes the masses of British coins to two decimal places so new coins can be used as calibration weights with about +/-10mg accuracy.

I have scales that auto turn off in few minutes. Yes super irritating when you have tared the beaker mass and did not write the mass down.

One more point some scales claim the resolution is the least significant bit of the display but in use they change by more than one count probably due to the limited resolution of the calibration calculation so get more resolution than you need.



[Edited on 1-5-2018 by wg48]
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[*] posted on 1-5-2018 at 13:22


I have one of these: https://www.amazon.com/American-Weigh-GEMINI-20-Portable-Mil...

I haven't tested it with a wide range of reference weights, but it seems to usually weigh within about 0.5%.




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[*] posted on 1-5-2018 at 14:10


Quote:
A typical task would be 100mg with an accuracy of 10%.


Indeed?

Well, giving the question the benefit of the doubt, these guys seem like a decent value:

https://ussolid.com/catalog/category/view/s/scales-and-balan...

I doubt they're on the level of a 'name brand' lab milligram scale, but they're also a tenth the price. Proper lab scales have power cords; you couldn't get me to go back to a battery powered scale for love or money. Leave it on, leave it warm (and stable.)

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[*] posted on 1-5-2018 at 17:55


What I am looking for is a nice mechanical scale.
No batteries to worry about, no power cord.

I've scoured ebay endlessly and have seen the
typical O'Haus triple beam balance many times.





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[*] posted on 2-5-2018 at 00:43


Quote: Originally posted by Gargamel  
Perhaps you can give me some advice or even suggest something.

To make it short, I'm looking for a proper scale to measure out very small amounts, not overstraining my limited budget (A contradiction, I know...).
Im just a guy that does some small scale experimentation at home, A "real" lab scale is out of question. Lets just say I'd like to spend 100€ or so.


There are many scales with 0,001g read-out on the market, but usually the vendors give little information about accuracy.

I have a workmate who uses one of the cheap 20g x 0.001g scales for his firearms hobby, so this is indirect knowledge;

1) If you are formulating your own mixtures then absolute accuracy is not required as it is the ratio of weights that is important.

2) For loading you do need absolute accuracy for repeatable muzzle velocities,
so get a calibration weight
(many of the cheap digital scales come with a suitable callibration weight)
Even if your calibrated weight is not absolutely accurate it does not matter,
provided that you use the same calibration weight each time you calibrate the scales,
for consistent results.

3) I have not come across cheap digital scales that do not auto-timeout.
Periodically, a small touch to the weighing platform prevents time-out.
I suspect that no-auto-power-off would be a choice for mains powered scales only.

Not sure, but I think that my friend's scales were reliable to +/- 3mg
and looked like this
20g.jpg - 54kB




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Gargamel
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[*] posted on 3-5-2018 at 07:02


Thanks for the answers.

Yes, the realoading guys also have this problem, I already read through such shops.

Quote:

1) If you are formulating your own mixtures then absolute accuracy is not required as it is the ratio of weights that is important.


If your scale behaves linear, OK. If not...Hmm.


I really want an extra scale for small amounts, I dont care if the limit is 10, 20 or 50g...
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[*] posted on 3-5-2018 at 07:34


I have not done a proper investigation but based on my 300g x0.01g scales,
I have a few calibration weights and whilst 'playing;
four 100g weights have such similar weights that I cannot identify them by weight using my scales,
using 50/20/20/10/5/2/2/1g weights together with the 100g weights has led me to believe that the RELATIVE error in the chinese calibration weights is less than the up to +/- 20mg hysteresis and randomness of my scales.

If I get a REALLY boring day I may do a more 'scientific' test,
but for now, I consider the linearity to be adequate.
==================================
even though I'm not allowed to play with energetics, so have zero experience,
I doubt that +/- 10% error is acceptable for firearms useage,
even 1% may not be quite good enough,
but you should check relevant websites because I know nuts.




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[*] posted on 3-5-2018 at 07:50


I don't know many reloaders, but the ones I do know use analog scales. This scale measures grains and is low capacity, but you can probably find one that will measure grams if you look around: https://ads.midwayusa.com/product/712103/lee-safety-magnetic...

You probably want a lab scale. They can be very expensive, but occasionally you hear about someone getting a good deal on a high-end older model.




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[*] posted on 3-5-2018 at 09:06
Used Ohaus Dial O Gram


I have had one of these for almost 40 years now. Still works great.

.001 G resolution, quick to use, much more handy than sliders for fractions of a gram.

And available on eBay used or even used and refurbished for less than $100.00.

s-l400-3.jpg - 20kB




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[*] posted on 3-5-2018 at 09:15


I haven't used one of those since high school :)



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[*] posted on 3-5-2018 at 09:20


I have a friend who also makes Edison brown wax
and early style cylinder records. He has an O'Haus
Dial-O-Gram scale which he brought along one time
when he visited my place.

The Dial-O-Gram scale appears to be very accurate at
its calibrated temperature of around 68 degrees F.

I demonstrated that it changes quite markedly
at a higher temperature. After doing a test with it
at an ambient temperature of around 70 degrees F. one
evening, we again tested it the next day when the
temperature had reached about 95 F. There was a quite
large variation.

I gather that this variation is due to the fact that
the "Dial-O" mechanism uses a spring. Springs
always vary their force as a function of temperature.

A plain beam balance which depends only upon
gravity will not have this variation introduced in this
particular way.

So, that's the one thing I'd be watching out for when
using the Dial-O-Gram scale. If it is always used
at a consistent temperature, it'll at least be repeatable.




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[*] posted on 3-5-2018 at 10:42


Maybe a local jeweler can help you with one or point you in the right direction, some use incredibly accurate 20g limit scales for weighing diamonds and gemstones.




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[*] posted on 3-5-2018 at 11:52


I did some extensive testing of this scale: http://www.dx.com/p/precision-20g-jewelry-digital-scale-0-00...
The factory calibration was within 0,2%, and with a quality wieght I was able to get it down to 0,1%. I did multiple full-range tests over the course of several weeks (transported it to work for tests), it was perfectly linear (to within 0,1%) throughout the range.




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[*] posted on 3-5-2018 at 14:45


Quote: Originally posted by sodium_stearate  
I have a friend who also makes Edison brown wax
and early style cylinder records. He has an O'Haus
Dial-O-Gram scale which he brought along one time
when he visited my place.

The Dial-O-Gram scale appears to be very accurate at
its calibrated temperature of around 68 degrees F.

I demonstrated that it changes quite markedly
at a higher temperature. After doing a test with it
at an ambient temperature of around 70 degrees F. one
evening, we again tested it the next day when the
temperature had reached about 95 F. There was a quite
large variation.

I gather that this variation is due to the fact that
the "Dial-O" mechanism uses a spring. Springs
always vary their force as a function of temperature.

A plain beam balance which depends only upon
gravity will not have this variation introduced in this
particular way.

So, that's the one thing I'd be watching out for when
using the Dial-O-Gram scale. If it is always used
at a consistent temperature, it'll at least be repeatable.


I have a check weight set for setting the ballance if doing anything where 1mg accuracy is critical. Especially when doing things with powder, I set the scale for the desired weight- Over the range from 0 to about 4.5 grams where most powder charges I use are, this will sometimes require offsetting the scale up to 2mg from the nominal setting.

Typically, reloading charges are given to the tenth of a grain. There are 64.8mg to the grain- The Dial O Gram 1mg resolution is overkill for a reloading scale. I also have an old but still functional Dial O Grain (same scale body, but calibrated in grains), this model is no longer made and usually costs a bit more if you can even find one.




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3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.

Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).

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[*] posted on 3-5-2018 at 15:13


I occaisionally use a gun powder scale



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[*] posted on 3-5-2018 at 18:25
$25.49 plus shipping, no batteries...


https://fsreloading.com/index.php?_route_=lee-precision-lee-...

Lee Precision safety scale. Mechanical scale, no batteries, magnetic damping, this and a check weight set will do what you ask.

90681LeeSafetyScale-228x228.jpg - 7kB




Rapopart’s Rules for critical commentary:

1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.

Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).

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