h a l f b a k e r yExperiencing technical difficulties since 1999
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The device consists of two parts.
The transmitter resembles a conventional
hydrometer made of sterilazable plastic. It has a
weighted bulb to which is attached a shaft. There is
an annular float around the shaft, retained by a
disk on the shaft end.
The float contains a pair of coils, but
is othewise
very buoyant, having a density of 0.1 or less.
The other component is a receiver which has a
simple LCD display.
The sensor is placed in a container of fermenting
wine or beer.
The sensor sinks until its density balances that of
the liquid. The ring floats on the surface.
A coil runs up the length of the shaft. As the ring
moves up and down, the inductance of the coil is
changed. Thus as the density of the liquid changes,
the position of the ring and thus the resonance
varies in proportion, as the winding of the coil is
non-linear.
The position information derived from the coil and
the temperature of the liquid are transmitted to the
display module twice a minute.
This allows the user to monitor the fermentation
non-invasively, reducing the risk of contamination
and spoiling.
The de luxe receiver can present a graphical
representation of density against time, thus
allowing the fermentation end point to be more
easily selected.
[link]
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So, the Borg make homebrew? |
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// Borg make homebrew? // |
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No, we have simply identified a previously
unexploited market niche. |
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The inductive float approach to level sensing
is under review. Optical methods are
promising. |
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The float might be better with a specific gravity of just under 1 or it would sit on the foam. |
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Anyway, doesn't the foam stick to everything, even the
hydrometer shaft, causing potential errors? |
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Yes. Got any bright ideas? |
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Yes...the weight loss during CO2 generation is around 4%, so...a
set of scales? |
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For a lower-tech approach, a series of cats could be
fitted with weighted belts, such that each cat sunk
at a particular liquid density. The density of the
liquid could then be measured by the number of
cats still meowing. |
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Ah, the Archifelis principle. |
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As the float moves up the shaft could you use induction to create electricity? Then use several hundred of these whilst brewing beer to help offset household electricity costs. |
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Oh, I think I've got an idea that won't be affected by the crud or dead cats: |
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Normally tank levels can be found by bubbling air into the bottom, and the pressure of the air, which causes the bubbles, represents the level of liquid after suitable calibration. It works well with liquids that kill most other sensors. |
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For the beer: two tubes which bubble air, an exact vertical distance apart. A manometer sits between the two. The pressure of one against the other is dependant on the density of the beer only. Even if everything gets crudded up, should continue to work. |
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Very like a pitot tube, then. |
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Arbitrarily limiting the vertical separation to
100 mm, the pressure difference will be 9.8 x
1000 x 0.1 = 980 Pa. |
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The change in S.G. during fermentation is
from about 1035 to 1015, about 2% or about
20 Pa. |
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Add to that the turbulence and noise from
the bubbles and the desing would be …
challenging. |
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I suppose if you used a U-tube manometer, the distance between the levels would be...100mm strangely enough(or around 140mm if Alcohol was used). If the tubes were sloped so that the meniscus travelled horizontally more than it travelled vertically, a 2% variation in S.G. could offer a difference of minimum 3mm between meniscii (sp?), depending on the angle. |
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Hey, go ahead, build a prototype- we're not
stopping you. |
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We're not saying it can't work, just that there
are a few aspects that will need very careful
thought … |
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Rather than sensing the meniscus … if you
have two parallel tubes, open at the bottom
and closed at the top by pressure sensors,
then the differential reading between the
sensors will be directly proportional to the
distance between the openings and the
density of the liquid. |
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The signal would be small, but no doubt a 741
Op-amp would do a reasonable job … |
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or use something powered by alcohol. |
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Wow...I just put a kettle of water on the stove to heat to make beer, and then refreshed the Halfbakery and here we are... |
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Well, (+) for concept but yes, the bubbles collecting on the device cause it to float higher over time, hindering accuracy. Perhaps small creatures that thrive in beer can be trained to knock these bubbles off for some reward. |
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//Perhaps small creatures that thrive in beer can be
trained // |
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Did anyone ever mention how big the Borg are? |
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