Real-Time Fermentation Monitor

Just don't forget to calculate and take into account the weight of the hydrometer tube full of liquid you are removing from each reading you take. That will impact the accuracy of the scale method of monitoring.

boyurboy said:

Just don't forget to calculate and take into account the weight of the hydrometer tube full of liquid you are removing from each reading you take. That will impact the accuracy of the scale method of monitoring.

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I'll take the OG reading before the original weight, and the FG after the final weight.

Coastarine said:

I'm going to just have a simple excel spreadsheet. I'll weigh the better bottle and any blowoff rig, enter that into the spreadsheet.

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I would recommend just doing your weights with the BB only. That way you don't have to worry how the blowoff rig is affecting the weight. It would be hard to guarantee that the same weight of a long tube is being counted after moving the carboy around.

Jonnio said:

I would recommend just doing your weights with the BB only. That way you don't have to worry how the blowoff rig is affecting the weight. It would be hard to guarantee that the same weight of a long tube is being counted after moving the carboy around.

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I don't really follow...if beer blows out the tube and into the jug then that still needs to be weighed, so the jug has to be on the scale. What are you worried about?

I'm probably going to rig a way to hang a water bottle on the neck of the carboy for the blowoff just to make it easier to weigh the entire thing.

Coastarine said:

I don't really follow...if beer blows out the tube and into the jug then that still needs to be weighed, so the jug has to be on the scale. What are you worried about?

I'm probably going to rig a way to hang a water bottle on the neck of the carboy for the blowoff just to make it easier to weigh the entire thing.

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I am following you now - I was thinking that the bucket of water wasn't going to be weighed, just the carboy and the tube. I was thinking that depending on the position of the tube you could get a different weight....That isn't the case though if your going to weigh the whole deal.

You may want to have way to stop or account for evaporation from your blowoff container too. I doesn't sound like your going to do a big bucket, but if there is a large surface area you may lose a lot of water over the course of a couple weeks.

I have thought about blowoff evaporation, but I usually use a jug with a pretty small mouth so I don't think there will be much. If there is, it shouldn't vary largely from batch to batch. All of these things like blowoff evap, dissolved CO2, and other things that might throw off the weight slightly but be consistent between batches will be compensated for by fitting an equation to reconcile the expected FG based on weight and the actual FG.

I wrote the spreadsheet, pretty simple so far. I'm going to plot the error between the measured FG and weight calculated FG versus OG, volume, empty weight, basically all of the starting values and look for trends. It might just be that the error comes out almost the same each time in which case I'll just average them and use it as a correction.

Parker36 said:

I was thinking about what The Kaiser said earlier about CO2 in the liquid screwing with the buoyancy of a submerged hydrometer type thing and was wondering how this dissolved CO2 affects a standard hydrometer reading and how large the affect is.

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This should pretty much be a non-issue except for the few hrs when fermentation is *really* vigorous.

Preliminary numbers are in!

Yesterday was a partigyle brew so I'm lucky enough to have two batches to run through this side by side. It's been about 30 hours since pitching and my yeast were off to a ROARING start. The brown ale was bubbling the blowoff tube before the red ale was even chilling. (OW=Original Weight of beer, fermenter, and blowoff. Don't worry, the spreadsheet subtracts the empty weight of everything for calculation but I just don't have that number)

Winter brown ale: OG 1.084 and OW 47.600lb -> 4.65gal
current weight: 46.025 lb for a calculated gravity of 1.043. (47% apparent att.)

Irish Red Ale III: OG 1.048 and OW 47.981 -> 4.76 gal
current weight: 47.038 lb for a calculated gravity of 1.024. (49% apparent att.)

At least it passes a sanity test so far!

edit: discussion continued here https://www.homebrewtalk.com/f11/weight-based-gravity-measurement-88821/#post956140

very cool please keep us posted.

This might be something I would be interesting once it has been tested more.

I am a patent attorney. If you want to talk about what's involved in patenting this, let me know via PM.