Can I use the Acaia Lunar scale to measure 100 mg precisely?

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Derryisreal
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#1: Post by Derryisreal »

Hi folks, so I bought an Acaia Pearl scale, which I like, but find too big, also, would love to make rpavlis water and instead of buying a mg scale, I was wondering if I should just upgrade to the Lunar, since it offers a high readability option of 0.01 g?
I really don't want two scales, don't want to make concentrate either, so my thinking was - if the Lunar can weigh 100mg of Potassium Bicarbonate precisely, why not get it? I like the premium feel of Acaia and would not go for a cheap scale.
Would love to hear your thoughts!

Thanks.
Light roasts are to me what garlic is to vampires.

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Jeff
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#2: Post by Jeff »

No, figure ±0.05 g at best (readability alone).

My experience with the Lunar 2021 is that it is an 0.1 g "accuracy" scale, examining the capture of the digital data over Bluetooth (including with the 0.01 scaling).

If you want to try direct measurement with 0.01 g accuracy, you probably need something with an air-current shield.

I recently bought https://www.amazon.com/gp/product/B011J88S8M/ at $35 and it seems reasonable. I still use it to weigh out "a couple grams" for 1000 ppm concentrates of 1 liter/kg size.

yertchuk
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#3: Post by yertchuk »

A gallon jug of distilled would require 0.3 to 0.4g of potassium bicarbonate for RPavlis water. Since it's not super critical the Lunar will be OK in my opinion. In fact I did just this for a while before switching to Crystal Geyser.

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GC7
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#4: Post by GC7 »

No! Weighing very small amounts with precision requires different scales and as Jeff mentioned, some kind of environmental shielding.

What I recommend is to weigh amounts within the accurate limits of your scale and make 100X or 1000X concentrated solutions. You then need an accurate method of liquid volumetric measurement to make appropriate dilutions of the components of your solution.

yertchuk
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#5: Post by yertchuk »

Can you really tell the difference in taste between, say, 0.35g and 0.40g of bicarb in RPavlis water? I certainly can't.

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Derryisreal (original poster)
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#6: Post by Derryisreal (original poster) »

Thank you all for the advice. I guess then I should rephrase the question - is the Lunar good enough, although imprecise, also, what would happen if I go above the 100mg per liter? Would the pH change dramatically, or just the taste would be affected?
I really would rather have only one scale, but if that is not feasible, I guess one more is in order :D
Light roasts are to me what garlic is to vampires.

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Jeff
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#7: Post by Jeff »

If you're shooting for a 20% accuracy, it probably doesn't matter much. For many people looking for a non-scaling water to feed their espresso machine with, reading to 0.1 g is probably OK if you're making several liters or a gallon at a time.

If you're making a liter or two at a time, I'd personally go with a concentrate approach as the amount for 1 liter is getting pretty small compared to a resolution of 0.1 g.

(Note that weighing the water making up the concentrate or the eventual dilution to much better than 1% is probably unnecessary to get 5% kind of accuracy end-to-end.)

If you're trying to decide if, for example, you like 60 ppm or 50 ppm KH and 40 ppm GH water better with your beans, grinder, and extraction profile, then you probably should look to a concentrate approach and a 10 mg resolution scale.

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Derryisreal (original poster)
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#8: Post by Derryisreal (original poster) »

Thanks, Jeff!
However, concentrates further confuse me. I am not sure what I should aim for. I am terrible at math.
Light roasts are to me what garlic is to vampires.

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Jeff
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#9: Post by Jeff »

Once you figure out the amount to add to your concentrate and how much concentrate to add, then it shouldn't be any worse than measuring directly.

For example, my "mix" is such that I use 10 g to get 10 KH* in a liter total. Figuring out that "magic number" of chemical to add to the concentrate bottle was the hard part. Now I have the amount to add in my liter concentrate bottle written on the side.

One thread with "numbers" already worked out is Easiest way to make rpavlis water?

* "KH" is one of the units that people use to measure brewing water

jpender
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#10: Post by jpender »

Jeff wrote:I recently bought https://www.amazon.com/gp/product/B011J88S8M/ at $35 and it seems reasonable. I still use it to weigh out "a couple grams" for 1000 ppm concentrates of 1 liter/kg size.
Sort of off-topic but I wonder if you could test something for me. I bought that scale a year and half ago. It was branded differently but was clearly the same hardware. I returned it because it behaved in a dishonest way. The firmware would sometimes fudge a nice rounded result. I can't find my notes but what I observed was that weights of, say, 9.990, 9.995, 10.010g would all be reported as 10.000g by the scale. This only happened near nice round numbers. I'm not sure why they would write the firmware to do that except that it would make it appear that the scale worked perfectly when calibration weights were placed on it. For me it was deal killer and I prefer my older milligram scale that doesn't lie to me.

I wonder if yours does this too or if the different branding also means different firmware. Can you try a similar test?