# Using electronic scales for running gravity reading



## ArgM (6/3/14)

Hey guys!

This is my first post, how exciting!

I'm studying Industrial Design and I am about to begin an electronics and prototyping subject.
With this I was hoping to adapt my assignments to make a simple electronic device that will record all the data coming from the brew to then understand 
what's happening where and how that relates and interacts with other parts of the process . I realise that their are very well down products and devices that already exist,
how ever, this is irrelevant since the main grading will be based on the efficacy of the electronics and the development of the prototype.

Now, I want to swing this one more for people using a simple set up and doing small batches, so they can fine tune in between each batch (I currently take 10 - 18L yield per brew). So, I am planning on putting in all the relevant temperature and volume readers from weighing the grain right through to carbonation. 

My question is: Would zeroing out the fermenter on a set of scales, working out the initial water gravity of the water to then find out OG by dividing its mass by the water reading, then using this reading to take a running gravity and FG reading be an effective and precise way of capturing the data electronically, with out manually siphoning and reading with a hydrometer?

Thanks


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## Toper (6/3/14)

It certainly would be.The only problem with a sample that size is that you need very accurate liquid and weight measurements.You'd need to calibrate the fermenter for volume to a very tight degree,and use scales that were accurate to withiin a very fine limit.Much easier to use a volumetric flask of 100ml (100ml=100g of water) and some jewellers scales that are accurate to within .000


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## ArgM (6/3/14)

Yeah, that 'accuracy' I think may be more effort over manual readings the more I think of it...
I guess that leaves me with powered siphon into a weighted scale to take the readings intermittently or finding a similar electronic sensor like in that 'BeerBug' Kickstarter?


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## Ducatiboy stu (6/3/14)

One wsy you could do it is to have a big balance scale setup. One side has your ferm and the other side has another vessel filled with water so they both weigh the same. As your brew ferments it will change in weight. You could then remove water from the water filled vessel to even them up, measure the amount of water removed and work out what the change is. You would need to acuratly weigh your fermenter first.

Be a PITA to setup but it would make an intetesting project.


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## ArgM (6/3/14)

That would be good, the issue with that is it would give an analog reading that I would then have to set something up to read and convert.
However, having said that, I'm sure there would be a 'reader' that could sit on the balance point that could do the job with that set up.
Also, if anyone know a way of measuring the complexity of sugar during mash that'd be cool to have


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## TheWiggman (6/3/14)

I reckon it's doable* provided you had an ultrasonic level sensor or similar to detect the height of the liquid before fermentation (krausen would dick around with it).

Consider a batch going from 1.050 to 1.010

Fementer - calibrate scales to be zero with it, including airlock and liquid
Original wort - 23l @ 1.050 = 24.15kg
Beer - 23 @ 1.010 = 23.23kg

As long as you know the actual volume, which you could calibrate pretty accurately from a ULS, if you had scales that were accurate to a gram then you could know your SG pretty accurately I reckon. It's a loss of 920g which is pretty substantial _observing the liquid alone._

*This assumes there are no solids in the liquid. Fermentation causes flocculation resulting in solids and yeast settling at the bottom. You're not actually changing the mass of the contents inside the fermenter but rather separating materials of different densities. Hence total mass may be 24.10kg after it's done, maybe, with the stuff at the bottom with an SG much greater than the FG. You're then talking about a 50g range to measure over, which is a different story. I'd be surprised if it's this much.

I'd maybe look at something buoyant on the inside held down by a load cell. As the density changes so would the measurement on the load cell, but then we're no longer in the 'simple' territory are we?


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## Ducatiboy stu (6/3/14)

You will loose mass with CO2 production.


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## Ducatiboy stu (6/3/14)

ArgM said:


> That would be good, the issue with that is it would give an analog reading that I would then have to set something up to read and convert


You could easly calibrate the centre pivot pointer in gms against a scale


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## Aydos (6/3/14)

Wouldn't the mass increase with the growth of yeast cells?


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## MCHammo (6/3/14)

aydos said:


> Wouldn't the mass increase with the growth of yeast cells?


No. The yeast eat the sugars, etc in the wort. They use the materials and energy from this to produce new cells. Since no new mass is being added to the fermenter during fermentation, the contents of the fermenter cannot increase in mass.


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## schrodinger (6/3/14)

Measure the CO2 loss, which will be directly proportional to the rate of sugar depletion and ethanol production. Easy in a fermenter. Put a CO2 sensor in the headspace and measure the air flow out via the airlock. The latter will require some cleverness -- maybe use a mechanical principle akin to a tipping bucket rain gauge. Or you can use a gas mass flow meter (but I assume cost is an issue and an MFM is pricey). 

Any way, the co2 flow is just the concentration times the flow rate. Too easy.


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## Grainer (6/3/14)

build A fermenter with a built in reader that can easily be sanitised at low cost


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## Ducatiboy stu (6/3/14)

Grainer said:


> build A fermenter with a built in reader that can easily be sanitised at low cost


and pressurised...and temp controlled...


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## schrodinger (6/3/14)

The other problem with a mass based approach is that you'll also lose mass through evaporation (via air that leaves through the airlock). To account for that would require an approach akin to what I described above for CO2 anyway.

In fact, the only mass you'll lose will be through CO2 (as noted by Stu), H2O and ethanol, except for a tiny loss of volatile organics. Everything else is just metabolism -- conversion of one thing to another, which will change density but not mass.


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## Ducatiboy stu (6/3/14)

I can see a Nobel Prize....or at least an Ignobel Prize in this project...

Would actually be interesting to see what sort of weight difference there is between begining and end of fermentation.


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## Mr. No-Tip (6/3/14)

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.


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## TheWiggman (6/3/14)

Schrodinger's got it, but it would be a bit of a ball tearer at those rates wouldn't it? It won't take into account any leaks. For me about every 2nd brew won't bubble through the airlock because the seal isn't perfect. 
I think the easiest way would be to do a high gravity, small batch with a strong yeast. Measure the change in mass following fermentation and correlate this to the change in SG. You should end up with a simple factor, which you could then plot on a graph as % of starting mass vs. change in SG. 

The other thing I didn't consider was losses due to evaporation (through the airlock). It would be minimal, but would be a function of temp and surface area and should still be considered.


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## schrodinger (6/3/14)

You're absolutely right, leaks could be a big issue. Easy to fix with some vacuum grease if you use a screwtop fermenter with o-ring. (Edit: or a carboy.)

Another way to measure flowrate is to replace the airlock with a resistive pathway of known resistance (perhaps a length of HPLC tubing) and measure the gauge pressure in the headspace. We do something similar to measure water flow in leaves. The biggest challenge here (assuming you've ruled out leaks) is to keep krausen from plugging the tube.


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## MastersBrewery (6/3/14)

This may be of some use LINK


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## ArgM (7/3/14)

MastersBrewing that looks pretty perfect!
I'm wondering if its worth using both the scales and the sensor? It sounds like both could offer small amounts of information.
The sensor should also give an indication of SG during mash and boil?


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## Econwatson (7/3/14)

If all you were wanting to do is find out the alcohol content, I always thought it would be cool if you could modify a breathaliser, and get an alcohol reading that way.


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## RdeVjun (7/3/14)

Beaten by MB, nevertheless IMO your most worthwhile solution is probably in densimetry. Unfortunately gross mass and volume sensing at this scale can be fiddly, it can be susceptible to environmental fluctuations such as temperature, humidity and electrical noise, plus accounting for evaporation and respiration is difficult, and that's presuming you can source affordable sensors and interface with the required precision.
Yes, densimetry would also have value in the mash and boil, so a solution could be more universal than just monitoring the ferment.

The Beerbug could be helpful- hope it doesn't rain on your parade too much?

This bubble counter might also be useful if you're wanting to monitor respiration rate, I never pursued it after seeing the light with cling film displacing my airlock bubblers.

In my day job we explored densimetry for continuous monitoring of suspended sediment in waterways, but sadly it never got very far off the drawing board due to the expense and experimental nature- for a short term project we couldn't risk the time it would take to develop a solution, so just reverted to conventional pumping samplers and event sampling etc., however I still feel it has some merit, particularly where remoteness or access is an issue.

HTH!


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## schrodinger (7/3/14)

So here are some numbers for the OP to chew on. If your wort had the equivalent of 4 kg DME in 20 L, the total mass loss as CO2 assuming 100% attenuation would be around 2kg, or 10% of the total mass. For a more realistic 70% attenuation, it's around 7%. So if your scale's precision is around 0.5% of full scale, and supposing it goes up to 50 kg, your daily change for a 7-day ferment would be approximately equal to the scale's precision.

Edit: I stuffed up the other calcs!


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## MastersBrewery (7/3/14)

RdeVjun said:


> Beaten by MB, nevertheless IMO your most worthwhile solution is probably in densimetry. Unfortunately gross mass and volume sensing at this scale can be fiddly, it can be susceptible to environmental fluctuations such as temperature, humidity and electrical noise, plus accounting for evaporation and respiration is difficult, and that's presuming you can source affordable sensors and interface with the required precision.
> Yes, densimetry would also have value in the mash and boil, so a solution could be more universal than just monitoring the ferment.
> 
> The Beerbug could be helpful- hope it doesn't rain on your parade too much?
> ...


Unfortunately Beerbug won't hold pressure, and calcs for escaping Co2 would really be come complex if we start presurising things at different temps, so densimetry or refraction are the only 2 methods I can see working


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## MHB (7/3/14)

Someone asked about this in the shop today. Had a bit of a think about it, the best solution I can come up with is to put a largish volume not too heavy sinker on a tether and suspend it in the brew from a load cell.
Archimedes worked this one out about 2000 years ago
Just to think through the process –
Say we took a bottle that was 1L and added filled it with sand until it just sank, i.e. massed 1.1Kg
Hang that from a scale with a thin thread (most modern lab balances have a hanging hook underneath and a USB or RS232 port)
In air the scale would read 1.1 Kg
Put it in water and it should read 0.1 Kg as it has displaced 1 L of water
Put it in 1.050 wort and it will read 0.95238 Kg (if it was exactly 1 L)
As the gravity falls you get les buoyancy so the apparent mass increases and moves back toward 0.1 Kg.
If you took a piece of stainless pipe and welded hemispherical ends on and tacked a length of fine SS TIG wire to supply the tether, (given you can weld) you would have a food grade, easy to sterilise sinker.
Naturally the bigger the volume of the sinker and the closer its density is to the wort the easier it is going to be to get accurate results, but you can get a 0.0001g scale for not much these days, if this is a uni project you could probably borrow one from the Chemistry department.
Mark


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## ArgM (7/3/14)

Hey MHB,

Yeah, I had that thought as I was going to bed last night that displacement and something to read the level of displacement should work... I can barely weld, but I'm sure I could give it a shot, can always use the practice! I guess I'd have to measure the mash at timed intervals manually as my pot isn't too big, but I'm in there cooking it anyway so no extra effort... I feel like a bubble counter would be a cool addition RdeVjun.
Talked to the lecturer today about it and it sounds like I won't be able to tailor the subject around it but any work done on it will be considered for additional credit! Which is pretty good considering Im recovering from a back injury and only doing that one subject this semester.

I might start another thread about this set of sensors and what information people deem important information and collecting and displaying the info, or we could tack it onto the end of this one? not sure about the semi off-topic thread roles!


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## MastersBrewery (8/3/14)

the problem being you would have to recalibrate for each batch or be dead accurate with batch volume to achieve repeatability, or have I missed something?


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## MastersBrewery (8/3/14)

Found this also Link though bubbles forming on the sensor may throw it out some as stated worth a try though


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## schrodinger (8/3/14)

MastersBrewery said:


> ...calcs for escaping Co2 would really be come complex if we start presurising things at different temps...


Why? CO2 loss = [CO2 concentration difference (e.g., micromoles CO2/mol air, i.e., ppm)] X [flow rate (e.g., mol air/minute)]. If flow is measured on a volume basis, it's easy to correct for pressure and temperature (moles/volume = n/V = P/RT). And since CO2 conc in the fermenter will very rapidly reach 100% whereas CO2 outside is negligible (~400 ppm), you could get away with only measuring flow rate.


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## ArgM (8/3/14)

Yeah, I didn't think about the calibration, would be near impossible during mash/boil where the volume is constantly changing...
Im beginning to wonder if looking at gravity might be the wrong way to go...

I've been playing the idea out in my head of using a sensor similar to the one diabetics take blood sugar tests on to read the level of sugar, as the beer ferments or mashes this sugar level should change, if I can match OG and sugar level at start of brew and FG and sugar level at end of brew I could then use the information for the sugar level in between as an indication of what the specific gravity was at a certain time. I could also take a SG reading randomly during fermentation and use this as a test reading?


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## ArgM (11/3/14)

Does anyone here have any experience with using a Ultrasonic Transducer?

_"Ultrasonic waves are passed from a source, through the fluid of interest, and into a detector which measures the acoustic spectroscopy of the waves. Fluid properties such as density and viscosity can be inferred from the spectrum." _http://en.wikipedia.org/wiki/Specific_gravity

There also seems to be a few Arduino compatible sensors and tutorials on setting one up... It seems like this would be a good way of doing, only downside will be translating the information into SG which Im sure will become easier with time


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## MastersBrewery (11/3/14)

I would think once you had spectrum differential across a sample of differing gravity "worts" a simple equation would spit out the SG all done on the arduino


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## ArgM (11/3/14)

True, this is looking like the way to go, found the sensor online for $6 so I reckon it's worth a shot!

Thanks everyone for your ideas and experience! 

Going to start a post documenting my process as I go through and put it all together, so if you wanna check out how it goes look that up! 

(probably get started in a week or so)


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## MastersBrewery (11/3/14)

I did see a link to a paper on the subject of ultra sound and liquid density, they wanted $35 for me to read it you may find you will need to play with a range of frequencies and returns to get one reading. Be very interested in your results, don't forget temperature variance.


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## MCHammo (12/3/14)

I started working on something to do exactly this; measure wort density using ultrasonic sensors. I got most of the way there, but gave up at the end for several reasons (one of which is that it isn't really necessary)

1. You need the longest possible path through the liquid to take measurements, as the time difference between two different densities is incredibly small. On that note,
2. You need very accurate, high resolution timing to even detect the differences. 
3. The sensor will need to be immersed in the wort to accurately measure the path through the wort. The sensors need to be resistant to water, alcohol, etc. (such sensors do exist)
4. Some US sensors (particularly these resistant ones) need a high driving voltage to operate. This presents its own problem with regards to driving circuitry (and propagation time through the circuitry). The sensors I tried needed 140Vpp to operate properly (and work at 40kHz). For that, I needed to construct a transformer to step 12V up to 140V.
5. The ultrasonic waves that you intend to send through the liquid will also travel through the container. They do so faster than through the wort, so you need to do some very smart filtering
6. The US waves do not like to reflect off a surface in the FV (at least in a plastic FV), so you need two opposed sensors.
7. Fermentation activity inside the FV will affect the time of flight of the US waves - suspended yeast, CO2 bubbles, turbulence, etc will throw off the readings.
8. As mentioned, temperature will affect the density of the wort. That's a relatively easy thing to measure and calibrate for, though.

I might have missed a few things, that's just off the top of my head.

Masters, can you give us a link to that paper? With any luck, my uni has a subscription to that publication and I can have a read of it myself


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## MastersBrewery (12/3/14)

MCHammo, it was a late night of trawling a week or 2 back, will see if I can retrace my steps to night


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## TheWiggman (12/3/14)

My experience with ultrasonic transducers is with solids, specifically thickeness measurements. MCHammo has covered everything I might be able to go on about - the variable you will be measuring is density. Typically for industrial application the speed of sound through a solid will range from 1500 - 9000m/s. You can get pretty accurate measurements off the time it takes to reflect the signal, which for a ceramic 5mm thick can be around 6 E -7 seconds. They will measure accurately to within +/-0.1mm if calibrated correctly. Albeit with a unit that costs thousands of dollars.

Water is around 1400 m/s (temp dependent). You could back-calculate from your result knowing the bulk modulous and time it takes to reflect off something in the wort. The biggest variance, in my opinion, will be the target you will be reflecting the sound off as it this isn't REALLY accurately set up your results will be inconsistent and innaccurate, _unless_ you knew the SG and temp to start with and tell the controller 'this is equal to this SG'. The distance could then be calculated and the rest of the work done from there. Of course like MCHammo said your sensor would be immersed which is not ideal.

Otherwise, for much more effort, you could place the target (say a stainless plate) in the bottom of the wort and have the sensor pointing at the solution from just under the lid. The biggest issue you'll face there is massive reflections from the suface of the water which will have to be somehow ignored, which is typically done using some sory of clever algorithm or graphing the results and determining which reflections should be considered. You then have two things to account for, being air and wort. And krasuen too I suppose.

I think MHB's suggestion is the best. There's more than one way to skin that cat.


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## MCHammo (12/3/14)

The setup I was going for two sensors (one Rx, one Tx) set in the walls of the fermenter, one on either side. That takes out a lot of the uncertainty of reflections, but reduces the time available to take the measurement (with a reflection off a solid surface, you've got about twice the distance - and hence time - to measure). What I was planning on doing was making a ballpark measurement of the ToF (Time of Flight) of the waves through the wort, and filtering out anything that came outside of those bounds (waves through the fermenter wall should arrive much sooner, reflections through the wort should arrive later). Once you establish a reading of the time, you can use that as an estimate of the time the next measurement should take (as the SG of the wort will change very slowly wrt the frequency of measurement). Setting up a band-pass filter on your Rx amplification circuitry works a treat, too.

By using submerged sensors, you take things like krausen out of the equation, assuming that the sensors are sufficiently submerged in the wort. The only problem that I see with MHB's solution, is that a decent load cell (last time I checked) was very expensive. You also don't know how the krausen and top-cropping yeast are going to affect the measurement.

Another approach we thought of was very similar to a refractometer - having a prism built into the side of the fermenter, and using a laser and sensors to make readings. The main problem for us, was one of resolution. We would have needed a very high resolution ($$$) sensor to pick up our laser beam, or a prism of very high refractive index (nothing we could find was high enough - and not opaque). We scrapped this idea, as it is pretty much impossible to do on a budget. The US approach is much more dfficult (and in the end may not even work), but is a much much cheaper option. And of course, as this thread has shown, there are many other options out there, too.


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## ArgM (12/3/14)

So, the sensor sounds like its more hassle than its worth, probably still gonna by one cause it sounds pretty fun to play with. 

Ive got a really rough concept of what I came up with in my musings today about it.
This is kind of what I'm thinking of doing but not savvy with different sensors and how to use them so if someone could help with that it would be appreciated.

So, you have a float gravity reader like the hydrometer with an open end, this is then held and floated in the keg, it is able to move up and down. Into the open end of this hydrometer
is a rod, this road is fixed to the roof of the vessel and cannot move, as the gravity changes the floating vessel will move up and down this rod which through the use of a sensor will be able to 
provide a gravity reading once calibrated.






also,


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## ArgM (14/3/14)

No Rod fans around?


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## MHB (15/3/14)

Actually its nearly what I suggested above, measuring the change in bouncy, except that you have added the extra complexity of moving parts where liquid could get in and change the mass of the float, you have to account for friction between the rod and the tube making up the stem of the hydrometer and any mass of dried on krausen that sticks to the tube...
You haven't suggested how you will measure the location of the "hydrometer" in relation to the rod and how any change in the total volume of the liquids will be accounted for (yes the volume will change - you cant take our a couple of Kg's as CO2 without something changing) as that will change the reference height from where you zeroed your readings
A more complicated and less accurate way to achieve the same thing - no not a fan of the Rod.
Mark

KISS


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## MHB (19/3/14)

In line digital Refractometers have come down in price dramatically, last time I looked at them they were around $14K now they are only about $3K.
If you had the budget they are really would be a brilliant choice, offering the ability to measure the mash, boil and with a bit of output manipulation the ferment gravity, here are some https://www.misco.com/refractometers/inline-process-Refractometer
Mark


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## ArgM (22/3/14)

3k is far beyond my reach at the moment haha, I'm having trouble scraping together for a burner!

I put my head together with a friend over a few beers with this the other night and we had an idea that seems like it's worth testing:






if the movement is consistent or a pattern is noticeable against gravity readings, it could be calibrated to turn the movement from initial position and change in velocity through liquid to give SG

An adaption to this would be to add a Flex sensor to the arm.

Now, there will be volume change due to C02 however, keeping in mind this is a domestic brew with volumes never larger that 25L, I was wondering how well a bubble counter could account for this change?


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## TheWiggman (22/3/14)

Not sure how this would work. An accelerometer will measure acceleration ie rate of change in velocity. To provide a reading it would need movement. What's going to make it move? Also accelerometers only read in one direction, and as it rotates the centripetal force will play around with readings and make them non-linear. 
Additionally, viscosity is the resistance to movement. Not sure if viscosity is consistent between brews but if different this is another external variable to account for.


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## hotmelt (22/3/14)

What if you were to measure the conductivity of the wort.Wouldn't that change as it ferments?


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## ArgM (22/3/14)

Hey Wiggman,

It would be in a casing which would be balanced to float correctly, as the wort changes this balance will change, the accelerometer should move and this movement should give information on speed and distance and that data is what Im hoping to match against gravity readings... That incorrect that they on read in one direction, they read x,y,z axis simultaneously. 
Yeah, viscosity could be an issue not only between brews but also in a single brew with heavier sediment falling to the bottom.

I'm not sure about conductivity, Id need to look into it, Id be afraid of electrocuting my beautiful yeast!


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## Kodos (22/3/14)

Mr. No-Tip said:


> 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.


Liar!

You're not married.


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## ekul (22/3/14)

Why not just leave the hydrometer inside the fermenter? I used to do this when i was too paranoid that draining some liquid out would pull 'infected' air into the barrel. Use gladwrap and just look in to monitor fermentation.


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## ArgM (22/3/14)

Hey ekul,

theres a few issues with that, the first being I want constant readings so I can observe the relationships between the different forces acting on the beer, with a traditional hydrometer it requires human interaction to get the readings, I played around with the idea of a hydrometer held by a sensor which could read the movement, however as MHB pointed out, it doesn't address change in volume from C02 loss and interfered readings from the Krausen. However, assuming from his last post he was picturing use in a much larger scale production where the changes in volumes would be much greater than for domestic purposes, so there may still be something in there if I can create an accurate bubble counter and find a way to account for C02 in between the wort and roof of vessel that may not have escaped, again, for domestic purposes this should be much easier.


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## hotmelt (22/3/14)

Have a look at homebrewtalk.com http://www.homebrewtalk.com/f235/can-even-done-measuring-specific-gravity-using-arduino-raspberry-pi-385352/ someone
there is trying to do he same.
Or there's these http://www.brewballstore.com/


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## TheWiggman (22/3/14)

ArgM said:


> Hey Wiggman,
> 
> It would be in a casing which would be balanced to float correctly, as the wort changes this balance will change, the accelerometer should move and this movement should give information on speed and distance and that data is what Im hoping to match against gravity readings... That incorrect that they on read in one direction, they read x,y,z axis simultaneously.


An accelerometer will only read measure along a single axis. The most common types have peizo-electric sensor in them connected to a small mass though a dampener. When something is accelerated along the axis of the dampener, it generates a voltage. Multi-axis accelerometers are available but they consist of multiple individual accelerometers and will have 3 outputs. Smartphones (and similar devices like a Wii remote) have 3 inside them to measure each direction. 

The movement in reality will be essentially zero, hence why I was a bit sceptical. You won't find an accelerometer that will measure what you're after. It's more likely to pick up vibrations from walking than movement from the arm rotating a few degrees over a few days.
When you say "balanced to float correctly" remember that unless there are two dissimilar fluids of different density in the wort, your float will either sink or swim. To address that you'd need a spring to stop the arm from rotating vertically, but again you can't really use an accelerometer. If you're going to use this method the floation force would be far simpler (and more accurate) to measure which puts us back to MHB's suggestions. Or maybe a circular potentiometer like a fuel tank, but then we're back in overcomplicated territory.


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## ArgM (22/3/14)

hmm, my thoughts were the same way displacement works, as the gravity of the liquid changes the location where the vessel holding the accelerometer will change, being on an arm controlling the radius this moves means two outputs are required, I wont be measuring the distance moved, but rather the rate in which it moves. By keeping it somewhere stable (so as to not be affected by passing footsteps or trains as I live right next to a train line). I simply need it to write to readings, an initial and a second reading to compare this against. 

So, say we have a reading of 300 initial, then it moves as the wort changes with the yeast we may see it change to 310, then return to 300. by observing these changes it may be possible to see a correlation between that and the SG.

I personally advocated the use of a flex sensor over the accelerometer, but the general consensus was that an accelerometer would be more fun to test haha

sorry, you are right, a multi axis accelerometer is what I meant when referring to multiple readings.


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## MHB (22/3/14)

Lets call it a thought experiment, what makes the accelerometer move up and down? It is either 1/ lighter than the wort so it floats to the top of the arc and stays there, 2/ heavier, so it sinks and stays there, or 3/ at neutral bouncy so it might float in the middle of the ark, until the gravity changes then it sinks = no data


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## ArgM (22/3/14)

How would there be no data from 3/ the gravity doesnt change immediately from OG-FG it will fall slowly, the moments of falling will create velocity and will give a data reading which the sensitivity will need to be calibrated to or am I missing something?

Those brewballs looking interesting and look like a solution that could work, I would only get stepped readings with those, but it could be possible to estimate the rate of change depending on the time between each ball falls


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## MHB (22/3/14)

Explain how this works and I will agree that you understand buoyancy


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## dent (22/3/14)

Took me a while to work out you were talking about buoyancy "wtf is bouncy?"

An accelerometer can measure a static angle well enough, based on the relative pull of gravity along an axis. The common ones available in digital form cheaply nowadays can produce an accuracy down to 0.3 degrees or so, in the units I have built.


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## glenos (22/3/14)

A very quick skim of the Brew bug webpage gave me this idea, what about a mass (ideally large surface area and small mass) suspended in the wort attached to a load cell? As the density of the wort changes the mass will float.

Or flaot your hydrometer in the wort and use a camera to capture regular images and process them to interpret the scale.


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## MHB (22/3/14)

Never claimed I could spell, specially later in the day spell checkers tend to get more an more retarded 
Mark


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## ArgM (22/3/14)

I watched the video, I have no understanding of buoyancy... from the top rated comment I gather, whilst the sand is in the top it want to fall side ways which is inhibited by the tube, when sand falls it is no longer top heavy allowing it to rise, the one with sand already at base sinks because it is top heavy.

Now, since we both agree that I dont understand buoyancy it would be nice for an explanation how an object that remains bottom heavy will not work give readings of velocity as the liquid around it changes? I don't know about you but I dont regularly turn my fermenter upside down...

I think Im going to continue with this and the brewballs (going to try and make my own) 

Remember, I'm new to all this, I'm studying Industrial Design, not engineering or science, I'm simply trying to find a way to do this an proposing experiments I think may work. I'm here to learn, not to say I have the answers to everything.


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## schrodinger (23/3/14)

ArgM said:


> ...if I can create an accurate bubble counter and find a way to account for C02 in between the wort and roof of vessel that may not have escaped...


Only around ~0.2% of the total CO2 from fermentation will be in the headspace (assuming wort with 4 kg DME, 5L headspace, 18 deg C, 100% CO2 in headspace, 80% attenuation).

- 4kg DME = 133 mol CO2... 80% attenuation = 106 mol CO2
- n/V in headspace = 0.04 mol/L of air... 5L headspace, 100% CO2 => 0.21 mol CO2


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## schrodinger (23/3/14)

BTW, because gas flow out of the fermenter (i.e., bubbling) is at steady state with CO2 addition to the headspace, which means the bubbling flow rate equals the rate of CO2 production. This means you don't have to measure CO2 concentration even during the first day, before the headspace becomes saturated with CO2.

There would be a small correction for the fact that the bubbles of CO2 emerging from the beer will also be saturated with water vapour (around 2.1% at 18C), so the CO2 production is really ~= 98% of the airlock bubbling rate.


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## ekul (23/3/14)

Schrodinger, i think your calculations are wrong. For 106 moles of co2 to be produced you'd need 53 moles of glucose to be fermented out which is 180.16 x 53 = 9.55 kg glucose.

if malt malt extract is 55% (quick search, probably wrong) maltose (which is 2 glucose molecules stuck together) and you get 80% attenuation the 4kg of dme would yield 9.76 moles of glucose ---> 19.5mol co2.

ArgM. If you knew the profile of your extract or grain you could probably just measure the volume of gas that is produced. 1mole of co2 takes up 22.4L volume @ standard temp and pressure.

You could just have an accurate flowmeter on the airlock and use PV = nRT to work out what volume is being produced, ferment @ 20C and you can assume that each mole of is 22.4L

Either that or just measure the CO2 loss with scales. 19.5 mole of CO2 is ~860g, a decent set of scales would be able to measure this.


You will have to check the composition of your extract (whether it be grain or malt extract) but it should be fairly easy to work out and how much the CO2 dissolves into the liquid. You could take manual gravity readings and correlate this with the loss of CO2.


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## MastersBrewery (23/3/14)

As stated in a previously linked thread tracking gravity by measuring CO2 output is accomplished more easily with a Mass flow controller and that some of these even calculate this volume for you. Obviously you'd need a starting gravity. Check the post by MalFet


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## ArgM (23/3/14)

Yeah, Ive managed to find a DIY Mass flow controller project online I think Im going to have a shot at as well

Ekul, how would you check the composition of the extract?


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## schrodinger (23/3/14)

ekul said:


> Schrodinger, i think your calculations are wrong. For 106 moles of co2 to be produced you'd need 53 moles of glucose to be fermented out which is 180.16 x 53 = 9.55 kg glucose.


My calculation was internally correct but it was the wrong calculation!


Here was my calculation:

4 kg DME x (1000 g DME/1 kg DME) x (72 g C/180 g DME) x (1 mol CO2/12 g C) = 133 mol CO2

As long as DME is 100% carbohydrate (C6H12O2 in whatever form -- maltose, glucose, etc), it will have 72 g C per 180 g DME. DME will have some other solids besides carbs, but I believe it's still over 90% carbohydrate. So the fact that it's 55% maltose might not be relevant. I suppose it depends on the yeast, but I always thought that unfermentables reduced attenuation, so this is already captured in the 80% factor. 


The total mass loss is the amount of CO2 produced by metabolising 3.2 kg of C6H12O2 (80% attenuation of 4 kg). First, find the mass of CO2 produced:

3.2 kg C6H12O2 x (72 kg C/180 kg DME) x (1 mol CO2/0.012 kg C) x (0.044 kg CO2/1 mol CO2) = 4.7 kg CO2


My mistake was forgetting that this is mostly anaerobic respiration, not aerobic respiration, so only one-third rather than 100% of the carbon leaves the system as CO2. So if you assume all the DME was consumed anaerobically, the correct answers are 44.4 mol CO2 and 1.56 kg CO2.


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## schrodinger (23/3/14)

ArgM said:


> Yeah, Ive managed to find a DIY Mass flow controller project online I think Im going to have a shot at as well
> 
> Ekul, how would you check the composition of the extract?


You'll want a mass flow meter, not controller. The beer controls the rate of CO2 efflux.


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## MastersBrewery (23/3/14)

schrodinger said:


> You'll want a mass flow meter, not controller. The beer controls the rate of CO2 efflux.


no actually the controller as it allows a set volume to escape at a set rate, this will also allow you to pressurize the ferment if you choose to do so the meter will not

Ed:

Mass flow controller
From Wikipedia, the free encyclopedia








A mass flow controller


A *mass flow controller* (*MFC*) is a device used to measure and control the flow of fluids and gases. A mass flow controller is designed and calibrated to control a specific type of fluid or gas at a particular range of flow rates. The MFC can be given a setpoint from 0 to 100% of its full scale range but is typically operated in the 10 to 90% of full scale where the best accuracy is achieved. The device will then control the rate of flow to the given setpoint. MFCs can be either analog or digital, a digital flow controller is usually able to control more than one type of fluid or gas whereas an analog controller is limited to the fluid for which it was calibrated.
All mass flow controllers have an inlet port, an outlet port, a mass flow sensor and a proportional control valve. The MFC is fitted with a closed loop control system which is given an input signal by the operator (or an external circuit/computer) that it compares to the value from the mass flow sensor and adjusts the proportional valve accordingly to achieve the required flow. The flow rate is specified as a percentage of its calibrated full scale flow and is supplied to the MFC as a voltage signal.
Mass flow controllers require the supply gas to be within a specific pressure range. Low pressure will starve the MFC of gas and it may fail to achieve its setpoint. High pressure may cause erratic flow rates.


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## schrodinger (23/3/14)

I know what a mass flow controller is, as I have a dozen or so in my laboratory. I don't know why you would want to pressurise the fermentation, particularly in a vessel that is not designed to withstand pressure, such as a glass or plastic carboy. 

If you used an MFC for this application, there would be nothing to measure: you would be imposing the rate of CO2 loss rather than measuring it. 

But go ahead and try it. Recommend you keep the kids away, as shards of glass from an exploding carboy will leave a mark.


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## TheWiggman (23/3/14)

Refer topic - what happened to the scales man?
Or maybe get a fermenter set up with:

Scales
Mass flow meter
Ultrasonic sensor
Float on load cell

Calculate average, then confirm with hydrometer. Then realise the hydrometer works pretty well


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## ArgM (24/3/14)

Thank god I have a plastic fermenter and no kids! 

I dunno, scales didn't seem as useful as first imagined..
Hopefully will get them all running, I want to try and observe how everything interacts, no clue what I'll do with the information beyond that though!


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## MastersBrewery (24/3/14)

schrodinger said:


> I don't know why you would want to pressurise the fermentation, particularly in a vessel that is not designed to withstand pressure, such as a glass or plastic carboy.


Perhaps you should enlighten your self then, or you could try the duck nuts. I'm well sure no one is stupid enough to pressurise glass( seems comical a lab rat would make such a suggestion), I believe most Commercial breweries use Stainless and if you'd read the link the user on HBT using the mass flow controller was using a sanke keg.


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## schrodinger (24/3/14)

The OP is using a plastic fermenter, as are the great majority of homebrewers.


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## TheWiggman (24/3/14)

Masters, the flow controller that MalFet is quoting in the link also has a meter on it. Like schrodinger says a meter is required to measure the mass flow, not a controller. Maybe MalFet's idea was to have the controller to maintain a certain pressure in the fementer (albeit bugger all) to ensure air cannot get back in before or after fermentation. Or otherwise coupled with a keg to pressurise the fermentation, is a pretty funky concept. It would require a pressure sensor though for feedback, because unless you know the exact rate of CO2 production, you'll never be able to sustain a constant pressure.
The next iteration of the WW perhaps?

ArgM, I still think the scales are feasible. It would be a piece of piss to trial provided you have the scales, so why not give it a go?


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## MastersBrewery (24/3/14)

MalFet was using a pressure transducer to read the pressure in the vessel and controlling that with the MFC, in either case a micro controller could easily do the math for you.

Ed: In any case it's a matter of how far down the rabbit hole one wants or dares to venture


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## hotmelt (24/3/14)

This might do the trick






Take initial reading with hydrometer,add weight to float,set up dial gauge, connect to PC then mark SG at needle of start point.Simple


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## TheWiggman (24/3/14)

Won't quite work hotmelt, the mass's force has to be equal to the float force. As soon as the SG drops the mass will fall.


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## hotmelt (24/3/14)

I meant to change that to - add weights to counterweight to sink float below surface then set up dial gauge to zero - then as SG drops the mass would move gauge.I clicked post instead of back ,no time to change.


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## TheWiggman (24/3/14)

hotmelt said:


> I meant to change that to - add weights to counterweight to sink float below surface then set up dial gauge to zero - then as SG drops the mass would move gauge.I clicked post instead of back ,no time to change.


If I understand you correctly, that still won't work. 
Once the float is below the surface it's buoyancy (which is relative to the fluid it's submersed in) will require a given force to hold it down. If it was under the water, then the downward force of the counterweight (mg) would have to be equal to that force as you've drawn it. So, once the SG of the wort increases, the float will require less force to hold it down; this will cause the counterweight to simply drop on the dial gauge. Well mostly, because the dial gauges have a spring in them to push the tip against the surface being measured. The spring isn't something I'd trust as reliable to do this role in this case. 
For this example, you would be better to ditch the dial gauge and simply fix a spring to the ground and use the meter at the top to measure the SG. Again though, the choice of spring would have a huge bearing on it's performance for reasons I won't go into. Think F=kx^2 from high school physics. 
As has been suggested above, measuring the force alone would be the best way to measure SG using buoyancy.


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## TheWiggman (10/4/14)

This may be the solution you were after, albeit without scales -

http://brewnanny.com/brewnanny-base-model/


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## ArgM (15/4/14)

Without watching the 20 min video, is there any where that describes how the BrewNanny works? Can't seem to find anything on the site that actually describes the product..


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## dent (15/4/14)

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.


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## 431neb (15/4/14)

Mr. No-Tip said:


> 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.


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## MastersBrewery (15/4/14)

dent said:


> 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.


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## dent (15/4/14)

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.


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## MastersBrewery (15/4/14)

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!


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## ekul (15/4/14)

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.


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## TheWiggman (15/4/14)

ekul said:


> 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?


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## MastersBrewery (15/4/14)

load sensor drift


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## ekul (15/4/14)

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).


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## TheWiggman (15/4/14)

ekul said:


> 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.
> 
> ...


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?


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## MastersBrewery (15/4/14)

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


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## ekul (15/4/14)

MastersBrewery said:


> 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
> 
> ...


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


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## ArgM (15/4/14)

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!


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## ekul (15/4/14)

ArgM said:


> 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.


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