Here's something someone needs to invent...

[psymn]

Just make your fermenter sit on the digital scale/transmitting device. Considering your fermenter has constant mass and volume you can recalc gravity of the liquid inside.

That would not work, because the mass of the fermenter would not change very much. The yeast uses some of the sugar to reporduce. So even though the density of the wort changes the overall mass of the container may not change much.

Anyone know how much CO2 is produced per kg sugar?

Matt

 

[Cheesefood]

That would not work, because the mass of the fermenter would not change very much. The yeast uses some of the sugar to reporduce. So even though the density of the wort changes the overall mass of the container may not change much.

Anyone know how much CO2 is produced per kg sugar?

Matt

I thought that gravity was more of a measure of viscosity than actual weight.

 

[SpecialEd]

Specific gravity is simply the ratio of the density of the wort over the density of pure water. Pure water is well known to have a density of about 1.00g/mL.
Mathematically this is written as

Density Wort(g/mL)
-------------------------= Specific Gravity
Density Water(g/mL)

Specific gravity is unitless because it is just a ratio. So since alcohol is less dense than pure water, and adding sugar to the water makes it more dense(now called the wort ) the change in specific gravity is used to estimate how far along fermentation has gone. The yeast change sugar into alcohol(creating CO2 as a byproduct) which lowers the wort density. So thats how it all works. I dont know how much co2 per kg of sugar, prob depends on the yeast strain, if you figure it out let me know. lolwow sorry this was long.

 

[TekelBira]

A diver's wrist mount wireless computer would do it. Temperature is readily available and recorded in seconds increments. Salinity can be calibrated to read as SG. Not cheap though...



And, no, I am not putting my dive computer in the fermentor to test.

 

[homebrewer_99]

A diver's wrist mount wireless computer would do it. Temperature is readily available and recorded in seconds increments. Salinity can be calibrated to read as SG. Not cheap though...



And, no, I am not putting my dive computer in the fermentor to test.

...also, woulnd't it burn your hand...???

 

[olllllo]

I just had a Fantastic Voyage flashback.

 

[newfie]

"I hear you. I just wanted to let you know that it could be around the corner. All we need is a geek on the inside that is a homebrewer and it could happen."


Hey my first post. The Temp thing would be a breeze. Thermocouple or RTD would be my recomendation. Little signal conditioning to a cheap analog to digital converter from national instruments and your away. For the Pressure ... How about using a pressure sensor at a known depth say 20 inches (deeper is better here) then signal condition and send to the converter and thats away. Its not that hard ... if your a GEEK.
right on

 

[SpecialEd]

Nice thought newfie I totally agree on the temp, as far a pressure I kinda thought about that as well but wouldent any pressure difference due to gravity considerations be negligible? We would need an extremely precise pressure sensor. The pressure difference on a hydrometer really isnt that much, and since liquid ethanol is being created wouldent the volume also be changing.
I was thinking maybe we could use elelectrical resistance. There would have to be a difference between the resistance in alcohol and water.
Or we could measure the CO2 pressure inside the fermentor (yes I know the airlock releases it). The pressure would increase slightly before it could blowoff. A graph of this would probably look like hills with cliffs(blowoff). We could subtract off these cliffs and integrate that area. We coul probably figure out a way to relate CO2 pressure area to how much alcohol has been created.

PS we ARE the geeks on the inside lol

 

[newfie]

Hey SpecialEd, Never calculated pressure diff on specific grav at that depth ... but prolly would be small, maybe too small to get resolution on. I like the Conservation of mass idea from fermentation equation. However isn't there more going on in the wort than just changing simple sugars to ethanol and CO2? Depending on the wort content, temp, yeast etc. It is a bit of a noodle scratcher. One of my old profs is a measurement genius .... maybe i'll ask him.

 

[SpecialEd]

newfie do it..im still in school..1year left on my physics degree so I overthink things too lol. Yeah there isa lot more than just CO2 and ehtanol conversion, reproduction, metabolism.... im def not a biologist. Just thought pressure wouldent change as much as we would need because as density(due tosugar) decreased volume (due to ethanol) would increase. CO2 would prob be similarly complicated to map mathematically but a CO2 sensor might be easier to use than a pressure...? lol although you sound like the electronics kind of guy, if you can come up with a pressure sensor id definitely be on board.

 

[runhard]

This forum is great, we have physicists, engineers, teachers, public servants, students, professionals, blue collar, etc. It is fun to see a simple thought move so quickly with everyone's input valued all for the one common goal......so I can monitor my fermentation at work doing no work. Some of the ideas so far have been great. I love reading these posts as it forces me to remember back to the old school days and also become familiar with newer technologies. Just my $0.02

 

[Schlenkerla]

A little item which floats in a bucket or carboy and transmits temperature and SG of the fermenting wort through a wire to an extrenal digital monitor.

You'd have to have some sort of special bung that the wire passed through with a hole for an airlock.

Wouldn't that be cool? Plus you could have an option for this thing to also be a thermostat for controlling heating and/or cooling. It could tell you the change in SG over the last 24 hours, maybe--making it very obvious whether a beer is still fermenting.

Any ambitious inventers out there?

I think it been done already!!!!

http://www.coleparmer.com/catalog/product_view.asp?sku=2575040

EW-25750-40
Digital Density/Specific Gravity Meter
Qty:

$2990.00 / each (USD) In stock.


Quite pricey though. Imagine how pissed off the SWMBO would be!!!!

 

[SpecialEd]

lol what does SWMBO stand for? And we are actually going forsomething that floats inside the fermenter and transmit data to a computer so we can waste time being anal and tracking how fermentation is going. But its been done so we now know its possible, good catchh Schlenkerla

 

[olllllo]

lol what does SWMBO stand for? And we are actually going forsomething that floats inside the fermenter and transmit data to a computer so we can waste time being anal and tracking how fermentation is going. But its been done so we now know its possible, good catchh Schlenkerla

Something that floats inside and wirelessly (nice to have) or wired meaures temp and specific gravity. Data could be logged to a computer/laptop.
To me it's the opposite of wasting time, becase once get the data at regular intervals, it's a set-it-and-forget-it thing.

It would only notify you if temp were out of wack, beer had reached FG or SG hasn't changed in x hours.

 

[SpecialEd]

lol right in theory thats exactly what it would do. I dont know about the rest ofyoou cats but if I have a gadget I am always messing with it. My guess is 50% of homebrewers would check it 3 times a day for the first batch.

 

[Levers101]

As far as measuring CO2 production the last thing you'd want to do is measure in the gas phase. Gases are a pain to measure, though a somewhat simple device that releases a constant volume and has a counter would do well in measuring volumes of CO2 released could be used.

In fact the simplest way to get at CO2 concentration is to measure the pH. Anyone who's had environmental chemistry knows that [CO2(aq)]~=[H2CO3*] with a Henry's constant KH = approx 10^-1.5 mol/L*atm. Knowing the alkalinity of the wort to start with and assuming the alkalinity doesn't change during fermentation (probably not a bad assumption as CO2 exchange doesn't change the alkalinity and the amount of electrolytes in solution aren't likely to change a whole bunch) then Alkalinity = (a1+2*a2)(KH*Pco2/a0)+[OH-]-[H+]. Since a0, a1, a2 are known as functions of pH as are [H+] and [OH-] and Alkalinity was measured and assumed constant, you can calculate Pco2 at any time. The actual amount of CO2 produced with time should then be able to be back calculated from your pH. Also, you have to assume that the partial pressure of the CO2 in the headspace in your carboy is at equilibrium with the fermenting beer. A slightly more complicated version would take into account non-equilibrium conditions and mass transfer, but I think it could be done. Of course any potential buffer effects by yeast would have to be sorted out, but all good models have to be calibrated and validated anyways...

All I'm saying is that its much easier to measure pH and get at CO2 concentration than to measure specific gravity directly. In fact, I bet that you could monitor pH and get as good of an indication of when active primary fermentation is nearing completion as by measuring specific gravity. This is because the pH should rise as less and less CO2 is produced by the yeasties.

There should be pretty close to a stoichiometric ratio of sugars consumed to CO2 and ethanol evolved from yeast on average.

Haha, a friend/co-worker has a $10,000 probe for taking realtime pH (and other) measurements in a stream. I'm sure it'd work just fine for this. It even has a turbidimeter, which measures turbidity, which would be useful to know when most of your yeast had settled out.

Cheers to NSF funding... it makes my graduate education possible.

 

[Regicider]

Great strategy, Levers101!

I'm not sure I'm with you on the pH rising as the yeast no longer produces gas. Wouldn't it just stay much the same as long as the carbon dioxide "blanket" remains in the vessel?

However, I agree that measuring the gas phase is not the way to go.


Now here's the basis for an idea for those of you still interested in density measurements:

• A hydrometer reading is just a level (height) reading which we convert to SG by means of a scale.
• There are electronic (optical) instruments for reading levels in tanks etc.

Make the instrument in the shape of a hollow cylinder with thick walls (open in both ends). It needs to be weighted so that it will "stand up" in the wort, like a regular hydrometer. Now put a string of, say, regularly spaced light sensors along the bore. (Photo diodes or some such might do the trick.) A similar string of LEDs could be placed on the opposite side of the bore, or you could rely on ambient light.

Now, above wort level, the light should have no trouble reaching the sensors. Below wort level, the sensors should detect much less light (this probably needs calibrating for a pilsner.) The voltage from the string of sensors would translate to a level reading, which can be calibrated for two points on the SG scale -- say pure water at 1.000 and a sugar solution of 1.100.

I don't know if this makes any sort of sense at all, but I've even drawn a diagram. It shows the top, cylindrical part of the instrument. The rest of the "payload" (temperature measurements, electronics) could be kept as ballast below the surface.

(You wouldn't necessarily need light detectors. Just a string of something that reacts differently to water than to air. Preferably something with an electrical output. Resistivity probes might do well.)

 

[SpecialEd]

Yeah Reg good thinking. It should work but remember we have to fit this through the neck of a fermentor. And this stuff would all require batteries and thus be heavy. Along with this weight we would have to make it bigger to be bouyant. So the lower the power requirements the better.
PS nice drawing

 

[Regicider]

Thanks.

What's a standard inner diameter for a carboy neck, then? About two inches? As long as you don't exceed that diameter, the instrument can be fairly tall before touching the bottom.

The LEDs don't require a whole lot of power. The circuitry for detecting (and passing on) the voltage from the photo diodes might eat up a bit -- I'm not really sure. Someone earlier in this thread talked about technology that could transmit power at radio frequencies (RFID, was it?). That might lighten the load considerably.

 

[opqdan]

Something similar to what you are proposing is probably the right direction to go. Out best bet is some sort of device that replicates the act of physically taking a hydrometer reading. The only change would be that this should work in clear liquids as well as semi-opaque (like a stout). Still though with the size of the LEDs and the sensors, the meter would not be super accurate.

Also, LED's would need to be chosen to produce as little UV light as possible so as not to skunk the beer (I believe that it is UV, correct me if I am wrong). I know LED's are not full spectrum and are pretty specific, but even a little bit can introduce off flavors.

 

[Levers101]

This is an abstract from the reference:

Becker T, Mitzscherling M, Delgado A. CHEMICAL ENGINEERING & TECHNOLOGY 24 (8): 61A-67A AUG 2001.

Title: Ultrasonic velocity - A noninvasive method for the determination of density during beer fermentation

Abstract: This contribution describes a new and noninvasive method for the determination of density during the primary fermentation of beer. A piezo crystal sensor is fixed at the outer surface of the cylindroconic tank and works as emitter and receiver alternatively. The ultrasonic signal passes the tormenter twice before triggering the time of flight measurement. Principle studies were performed, which point out the applicability of the system. In particular interferences, which occur during beer fermentation, were characterized. A strong sensitivity exists to changing temperature and the concentration of diluted carbon dioxide. In this special application no dependencies on dispersed microorganism or gas bubbles in the media could be observed. A signal filtering system as well as a calibration method were developed. Finally, the measurement system was tested under technical conditions for the on-line supervision of density during a fermentation process at an industrial plant. The results obtained were in representative agreement with the values of a standard reference method with mean standard deviation of about 0.7 degrees Sacc extract.

I can't find the full text anywhere though. I go to the source and it lists pages 61A-67A which I cannot find.

Note that this work was produced by Tech Univ Munich and the corresponding address is Weihenstephan, Germany.

 

[Regicider]

I found the full text, but the site requires a license. Fortunately, the library at my university has one, so the article now rests on my HD. PM and ye shall receive.
(It looks interesting, but also fitted to large scale production. Can you say 400 cubic meters?)

And opqdan: how about a string of resistivity sensors instead? I'm pretty sure the resistivity of air is higher than that of wort in any stage of fermentation...

 

[cweston]

I have nothing to add to this discussion at this point--I just wanted to point out that I'm brimming with pride for having started a thread that has now exceeded 50 posts!

 

[johnoswald]

brim a little more since this is 54!

and also since cheesefood chimes in every now and then with his avatar
is that his swmbo or dream?

 

[opqdan]

I found the full text, but the site requires a license. Fortunately, the library at my university has one, so the article now rests on my HD. PM and ye shall receive.
(It looks interesting, but also fitted to large scale production. Can you say 400 cubic meters?)

And opqdan: how about a string of resistivity sensors instead? I'm pretty sure the resistivity of air is higher than that of wort in any stage of fermentation...

I think that would be a much better solution, and would also be easy to build and use.

A piezo crystal sensor is fixed at the outer surface of the cylindroconic tank and works as emitter and receiver alternatively. The ultrasonic signal passes the tormenter twice before triggering the time of flight measurement.

This sounds awesome. Not only is it designed for beer (so it would be acurate enough), but it seems that it would be low power and small size. I wonder if we could do something similar, based of of this research. The big difference is the batch size (we'd want it to work with 5 gallons, and it wouldn't need to work with much bigger).

hmmmm.... I've ben thinking lately about going on to do graduate work after I graduate in December (computer engineering)...


***ETA: I found this little gem over at the Got Mead forums: http://www.gotmead.com/component/option,com_smf/Itemid,103/topic,1192.0
It is an actual experiment that was done with using the mass of the carboy for the calculation of the specific gravity. As time goes on, the error in the value rises, but we could correct for that. This looks promising.

This is the scale that I think he used. Still a bit pricey, but it has a semi remote display (it can be mounted a couple feet away, corded). {whoops... I forgot the link and now I don't have it. you can find the name in the thread though}

 

[Cheesefood]

brim a little more since this is 54!

and also since cheesefood chimes in every now and then with his avatar
is that his swmbo or dream?

My swmbo is my dreamwoman. This is just a little eyecandy to make everyone's day a little brighter.

 

[olllllo]

Discontinued per the mfg page...

Designed for economical weighing and inventory tracking of draft beer usage, the Ohaus Mariner combines durable construction with easy-to-use digital electronics and custom software utilizing the specific gravity of beer. The low-profile design of the base offers low lift height for handling kegs. One-button operation, fast electronics and bright display make the Mariner quick and easy to operate. Long-length, durable power and indicator cords allow the Mariner to be positioned as required for everyday use. For quick weighing and inventorying of draft beer at an economical cost, the Mariner is the right choice.

http://www.scalesonline.com/detail.aspx?ID=349