Using electronic scales for running gravity reading

[dent]

Near as I can tell they release the CO2 at a certain measured pressure and attempt to use that release timing data to estimate your fermentation progress. Pulling a long bow with that I reckon.

 

[431neb]

I use a hydrometer.
And sleep in a bed with my wife.

Nah, just kiddding. Sounds interesting. I'll be interested to see if this goes anywhere.

You use a hydrometer on your wife when she sleeps in a bed?!!

Oh, my bad. As you were.

 

[MastersBrewery]

Near as I can tell they release the CO2 at a certain measured pressure and attempt to use that release timing data to estimate your fermentation progress. Pulling a long bow with that I reckon.

Actually probably accurate to 0.5 of a point, of course you would have to give it an accurate OG to begin with, CO2 correlates directly to the amount of alcohol produced/ sugars consumed by yeast. There is already a doodad on ebay that does the same thing, weirdly it allows the CO2 to inflate a balloon to a certain pressure and release it, counting how many times it is inflated and correlating this to gravity points lost. Obviously these measurements are all dependent on temperature and I note both have temp sensors on board. As long as you can measure temp, volume of CO2 produced, and have an OG, the rest is high school math, an R'PI wouldn't get warm doing the calculation.

 

[dent]

Yeah but,

• It relies on a very small pressure measurements in vessels of unknown materials - the flexibility will change the volume of the vessel with increase of pressure on some vessels, not much others
• The temperature changes the pressure/moles relationship
• The measurements are of very small quantities, and there are many measurements - maybe that improves it? not sure.
• The wort itself absorbs a certain amount of CO2, which relates to temperature and maybe the strength of the wort too?
• Wort fermentables are consumed during the yeast aerobic phase which does not generate much CO2
• Assumes perfect seal on the fermenter - how many air lock not bubbling threads are there?

I dunno, it seems like there are a lot of variables. Maybe they have gone to the trouble of controlling against all of them but I've seen plenty of prettily designed products which would work wonderfully if it wasn't for those pesky laws of physics.

I think CO2 measurement can be a great estimator of ferment progress, I just don't know about using it to get your actual gravity reading, at least in this setting.

 

[MastersBrewery]

I agree with a lot of your points, from what I understand brew nanny holds the fermenter at constant low positive pressure, it measures and controls the temp, so alot of the problems are as I said mathmatical. I'd agree with the ferment seal. Flexibility is insignificant with volumes of CO2 produce.

The advantage is without touching the fermenter you can see your within a few points of terminal gravity and if gravity is stable over days. Most of us wait (like I am ATM) 10-14 days take a sample and see where it's at, too high, leave it a few days, check again, ect ad-nausea. If I check at 14 days and I'm at terminal gravity, the question is how long has it been there, are my techniques effective, did it ferment out in 5 days create high fussel alcohols, then sit on lees for a week? I can't say. Some guys here use refractormeters to measure gravity they convert from Brix use an adjustment for alcohol and temp compensation to get an FG, how accurate a figure is the result of all that math?

End of the day being within a point or 2 so you can move to the next step is all that is really required. Still I'd be using keg lube to help ensure that fermenter sealed!

 

[ekul]

to measure co2 loss you could just weigh the fermenter, no need to measure the amount of gas coming off. Measuring the volume of the gas coming off would be inefficient as the volume would change as the temperature changes. However the weight of the co2 being lost will always be the same.

 

[TheWiggman]

to measure co2 loss you could just weigh the fermenter, no need to measure the amount of gas coming off. Measuring the volume of the gas coming off would be inefficient as the volume would change as the temperature changes. However the weight of the co2 being lost will always be the same.

Check out the thread title and head back to post #1. How much?

 

[MastersBrewery]

load sensor drift

 

[ekul]

well, say you make 23L of beer and its 5% abv. That means you have 1.15L of pure alcohol. density of alcohol is 789kg per cubic metre. 1000L to the cubic metre. 789/1000 x 1.15 = 907 grams of alcohol. Molar weight of alcohol is 46.07g So for a 5% brew you have 19.69 moles of alcohol.

For every 1 mole of alcohol produced you also produce 2 moles of CO2. Molar weight of CO2 is 44.01g.

If you make 19.69 moles of alcohol you make 39.38 moles of CO2. 39.38 moles of CO2 weighs 1733.11g

So for a 23L brew at 5% your weight difference should be 1.7kg. I'm drunk though so someone should probably check these figures.

edited to add~ You may need to check the solubility of CO2 gas in your liquid at a certain temps, however as a fully carbonated beer is 2.2volumes (or whatever) this should only equate to around 90g of co2. Wort is nowhere near fully carbonated though (obviously).

 

[TheWiggman]

well, say you make 23L of beer and its 5% abv. That means you have 1.15L of pure alcohol. density of alcohol is 789kg per cubic metre. 1000L to the cubic metre. 789/1000 x 1.15 = 907 grams of alcohol. Molar weight of alcohol is 46.07g So for a 5% brew you have 19.69 moles of alcohol.

For every 1 mole of alcohol produced you also produce 2 moles of CO2. Molar weight of CO2 is 44.01g.

If you make 19.69 moles of alcohol you make 39.38 moles of CO2. 39.38 moles of CO2 weighs 1733.11g

So for a 23L brew at 5% your weight difference should be 1.7kg. I'm drunk though so someone should probably check these figures.

Quiet Tuesday on the brews?
Bust out the scales ArgM. This is basically what you were asking for the whole time. How did it all descend into buoyancy, ultrasonics and CO2 measurement?

 

[MastersBrewery]

ok simplistically 23L of 1.050 wort weighs 24.15 kg and 23L of 1.010 wort weighs 23.23kg
at the beginning of ferment you add 7-12G of yeast
Now at the end of ferment we have a crap load more yeast/ trub together probably slight lighter in weight by volume than the sugar that's been consumed. I note the total volume with in the fermenter may have reduced by 50-100ml, most of this I'd write off to evaporation

Most of us write 2L off to losses in the fermenter but a lot of this is liquid with solids (yeast and trub) suspended if we were able to separate these solids I'd say you'd maybe be short 300ml all up. so 22.7l of 1.010 is 22.97kg

It would be interesting to check og/fg fermenter weight

 

[ekul]

ok simplistically 23L of 1.050 wort weighs 24.15 kg and 23L of 1.010 wort weighs 23.23kg
at the beginning of ferment you add 7-12G of yeast
Now at the end of ferment we have a crap load more yeast/ trub together probably slight lighter in weight by volume than the sugar that's been consumed. I note the total volume with in the fermenter may have reduced by 50-100ml, most of this I'd write off to evaporation

Most of us write 2L off to losses in the fermenter but a lot of this is liquid with solids (yeast and trub) suspended if we were able to separate these solids I'd say you'd maybe be short 300ml all up. so 22.7l of 1.010 is 22.97kg

It would be interesting to check og/fg fermenter weight

it would be hard to do this calculation purely from og to fg because your volume will change from the co2 loss. The co2 will have a volume in the fermenter but i dont know what this volume would be. Evaporation loss should be fairly low if the fermenter is sealed. If evaporation was a concern airlocks would go dry several time during fermentation.

the trub amount shouldn't make a difference to final weight because it should be there originally. The only thing I'm aware that gets lost from the ferment is the co2.

I'm not 100% sure that 1.7kg of co2 would lost as maybe there are other pathways to alcohol.

I'm going off the formala Sugar --> 1 ethanol + 2 CO2

 

[ArgM]

Where were you all when the naysayers came at the start!
I'm going to be trialing the scales as well as a bubble counter I've knocked up with my next brew which, having been put off for about a month I think I should do this weekend!

 

[ekul]

Where were you all when the naysayers came at the start!
I'm going to be trialing the scales as well as a bubble counter I've knocked up with my next brew which, having been put off for about a month I think I should do this weekend!

i think i replied to this thread but instead of putting the weight i put the volume of gas that would be released. I saw it again and thought maybe the weight difference would be more of use.

Please report your findings, i'm very interested to see what happens.