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Topic: Taking a shot at specific gravity measurements (Read 4 times) previous topic - next topic


People can read the posts and they will realize you started the arguments when I contradicted your opinion. That's taking it pesonal and you keep doing it over and over. You did said "brainstorming" I mentioned was bs. It was you. I even said that your load cell thing was a good thing then; but like with anything else there were problems with the hook up string. You were also the subject of the argument there. It has been you alll the time. Now you are calling me old, young and a bunch of other things that just make me laugh, just because I desagreed with your opininon. Isn't that taking it pesonal? Remember stay proffessional and argue with science not with insults they aren't going to make you prevail. When I said No one voted I meant no one mentioned your load cell, except me by the way...
Buoyancy ("vouyancy" hahaha thanks fo the clarification on the spelling) is not something that difficult to understand, that's why its taught in elementay I guess, so don't be so possessive about your knowledge on that.  Take it easy we all learn with all this.
Perseverance is 90% of the solution. The remaining 10% is more perseverance.


Not a moving part. You lower a weight into the liquid and tie the string to a force gauge.

I assumed that you would be dipping it rather than leaving it immersed, but you know what they say about people who assume. I thought that would be the only sensible way to get rid of the unpredictable variable buoyancy effects from bubbles collecting on the wetted surfaces.
I only provide help via the forum - please do not contact me for private consultancy.


Didn't realise it was a poll. It's a perfectly feasible solution, and the only thing I don't much like about it is that it seems to require moving parts which I think would be problematic in a hygienic environment. And just about all the other solutions being suggested suffer from a similar problem.

Well, this other guy is doing a vote all by himself, apparently that is what he considers as a vote. I must have not learned my English well enough. Sounds like communist vote. One person votes :)

You insist in being non proffessional...
Perseverance is 90% of the solution. The remaining 10% is more perseverance.


Feb 04, 2013, 11:28 am Last Edit: Feb 04, 2013, 11:49 am by Twinnie Reason: 1
I'm glad everyone's as passionate about SG readings as I am.

On the other hand I'm now thinking about using a sampling method. The advantage of this is that I can keep everything out of the fermenting bin which will help in sanitizing the whole thing and I'll also be able to move it all to another bin without quite so much effort. The disadvantage is it it will have a pump and added complexity which will make infection more likely but since it's modular I should just be able to submerge the whole thing into sanitizing fluid. Aquarium pumps are used in homebrewing a fair bit so they can't be that bad, you can get those ones that just squeeze the tube whatever they're called and they should be simple to clean.

My plan would be to have the pump suck up the wash for a while and which would be filling a container until it is full and then the rest (including yeast head) will all wash down the side and run back into the bin. Then I would just measure the weight of the container. This way the mass would be constant and I wouldn't have to worry about the bubbles or variation in the liquid volume.

My only concerns are that weighing the liquid might be tricky while trying to keep the whole thing sealed (to prevent contamination) and I'd have to have some kind of valve to release the liquid from the container afterwards. I was also concerned about sediment settling and screwing up my measurements but I figure I can program some kind of cleaning routine after a measurement and have the pump blast it all away by opening the valve and rinsing it all out with. There's also the concern of having the measurements disturbing the fermentation while it's conditioning. It won't be a problem during the early stages but later on I'll have to limit the readings to something like twice a day and try to minimize how much it disturbs the sediment that's already settled.

Come to think of it, couldn't I just make the container tall and thin and bring the pressure sensor back into play? That way I wouldn't need to worry about isolating the container for the purposes of weighting it and I just use some kind of pinch valve to close the bottom since I wouldn't have to be thinking about balancing it on another sensor or anything.


Weighing the liquid itself is a good method; but in your case (as you mentioned) there are several inconveniencies. On the other hand, to use this method in a reliable and consistent way you need to be very precise in the volume of liquid you are weighing. To keep the volume nearly constant everytime the measurement is done by pumping can be difficult to achieve. In the "thin and tall column" there will also be evaporation reducing the amount of liquid and therefore its weight affecting the specific gravity calculations. You won't be able to determine if the change in weight is due to density change or evaporation. The main problem is that several factors not only specific gravity changes are affecting the System under measurement. That's why this is normally done by taking a known volume sample of the liquid and weighing it or dipping in an specific gravity measuring bulb and observing how much it sinks. These two methods remove all other influencing variables. In the case of the floating device that is achieved by placing the scale in the device itself.
Perseverance is 90% of the solution. The remaining 10% is more perseverance.

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