We got on this discussion in this thread: https://www.homebrewtalk.com/f11/real-time-fermentation-monitor-85661/index2.html This post contains no new information that isn't in that thread, it just gives me somewhere to document my scribblings without further contaminating an otherwise very scientific thread.
For a summary, I'm using the definition of specific gravity, and so the definition of density, to try to monitor gravity without having to pull a sample of beer. You might be asking yourself "what's the advantage of this?" Well I'm sure that will make itself obvious.
When it does, someone please PM me or something. Maybe it will be a good way to know when fermentation is done, then you can take a sample to get a more accurate FG reading. I dunno, I just want to see the concept work.
In the mean time I picked up a cheap postage scale on ebay with a 76lb capacity and 0.2oz resolution. I weigh the empty fermenter and any blowoff rig or airlock during the boil, then take a gravity after chilling, fill the better bottle, pitch yeast, and weigh the whole thing again. Gravity -> density, and weight/density -> volume. After fermentation, weigh again. Assuming volume stays the same (can anyone confirm that?), then Weight/volume = density -> gravity. Ta Da! Of course I made a handy excel spreadsheet to do the math.
Naturally it is important to not put anything into/take anything out of the blowoff jug or fermenter. Also, I expect some error from things like evaporation of the blowoff jug water, maybe the CO2 still in solution, and I'm sure things I haven't forseen. With any luck, the error will be consistent and predictable in some way.
The first two iterations of this are underway. I brewed a partigyle two days ago. The strong beer measured 1.084 and weighed in at 47.600 lb minus the empty weight, putting the volume at 4.65 gal. About 30 hours later it weighed 46.025 lb which puts the gravity at 1.043 and 47% apparent attenuation.
The weaker beer measured 1.048 and weighed 47.981 lb for a volume of 4.76 gal. After 30 hours it weighed 47.038 and a calculated gravity of 1.024 and 49% apparent attenuation.
That's all for now, I'll give them a few more days and weigh again. So far I can at least say that the numbers are reasonable.
For a summary, I'm using the definition of specific gravity, and so the definition of density, to try to monitor gravity without having to pull a sample of beer. You might be asking yourself "what's the advantage of this?" Well I'm sure that will make itself obvious.
When it does, someone please PM me or something. Maybe it will be a good way to know when fermentation is done, then you can take a sample to get a more accurate FG reading. I dunno, I just want to see the concept work.
In the mean time I picked up a cheap postage scale on ebay with a 76lb capacity and 0.2oz resolution. I weigh the empty fermenter and any blowoff rig or airlock during the boil, then take a gravity after chilling, fill the better bottle, pitch yeast, and weigh the whole thing again. Gravity -> density, and weight/density -> volume. After fermentation, weigh again. Assuming volume stays the same (can anyone confirm that?), then Weight/volume = density -> gravity. Ta Da! Of course I made a handy excel spreadsheet to do the math.
Naturally it is important to not put anything into/take anything out of the blowoff jug or fermenter. Also, I expect some error from things like evaporation of the blowoff jug water, maybe the CO2 still in solution, and I'm sure things I haven't forseen. With any luck, the error will be consistent and predictable in some way.
The first two iterations of this are underway. I brewed a partigyle two days ago. The strong beer measured 1.084 and weighed in at 47.600 lb minus the empty weight, putting the volume at 4.65 gal. About 30 hours later it weighed 46.025 lb which puts the gravity at 1.043 and 47% apparent attenuation.
The weaker beer measured 1.048 and weighed 47.981 lb for a volume of 4.76 gal. After 30 hours it weighed 47.038 and a calculated gravity of 1.024 and 49% apparent attenuation.
That's all for now, I'll give them a few more days and weigh again. So far I can at least say that the numbers are reasonable.
