Method for detecting Ethanol in solution?

Discussion:

(too old to reply)

Evan

2007-06-13 21:36:30 UTC

Hi all, coming from an electronics/engineering background so I
apologize if there's an easy answer to this, I haven't come across it
yet...

I'm interested in being able to sense/measure alcohol fermentations
in
a hobby situation, say home brewing or winemaking, where normally one
would have to open the vessel and take samples in order to see
specific gravity via floating hydrometer or hand held refractometer.
There are a number of problems involved, one being tha the solution
of
course is not just alcohol and water, there are many other chemicals
present, as well as sediment, yeast and other things that impinge
upon
clarity (Which I think would preclude the near-IR sensor that I saw
someone mention in this group's archives)

I have not seen any comercially available sensor that measures
ethanol
in solution directly; i was thinking perhaps capacitance or
resistance
could reliably be an indicator, but as I mentioned before there are
acids among other things present which I'm sure would render that
kind
of reading useless.

The only thing resembling a lead I have is using infrared to observe
the CO2 bubbles leaving the air-trap on top of the sealed vessel; if
I
could get a reasonable estimate of the volume per bubble I think I
could work backwards through fermentation chemical formulas to arrive
at the portion of alcohol being produced. Now i'm wondering if I
could find some sort of sensor that does ethanol vapor (e.g., a
breathalyzer type sensor) and expose it to the CO2 exhaust from the
fermentation and get a reliable reading there, then i would just have
to make some correlation between the reading in the vapor and what is
in the emitting solution.

Any thoughts would be greatly appreciated; I'm sure there's a good
way
to do this, just have to find it...

d***@hotmail.com

2007-06-13 23:23:39 UTC

Permalink

Post by Evan
Hi all, coming from an electronics/engineering background so I
apologize if there's an easy answer to this, I haven't come across it
yet...
I'm interested in being able to sense/measure alcohol fermentations
in
a hobby situation, say home brewing or winemaking, where normally one
would have to open the vessel and take samples in order to see
specific gravity via floating hydrometer or hand held refractometer.
There are a number of problems involved, one being tha the solution
of
course is not just alcohol and water, there are many other chemicals
present, as well as sediment, yeast and other things that impinge
upon
clarity (Which I think would preclude the near-IR sensor that I saw
someone mention in this group's archives)
I have not seen any comercially available sensor that measures
ethanol
in solution directly; i was thinking perhaps capacitance or
resistance
could reliably be an indicator, but as I mentioned before there are
acids among other things present which I'm sure would render that
kind
of reading useless.
The only thing resembling a lead I have is using infrared to observe
the CO2 bubbles leaving the air-trap on top of the sealed vessel; if
I
could get a reasonable estimate of the volume per bubble I think I
could work backwards through fermentation chemical formulas to arrive
at the portion of alcohol being produced. Now i'm wondering if I
could find some sort of sensor that does ethanol vapor (e.g., a
breathalyzer type sensor) and expose it to the CO2 exhaust from the
fermentation and get a reliable reading there, then i would just have
to make some correlation between the reading in the vapor and what is
in the emitting solution.
Any thoughts would be greatly appreciated; I'm sure there's a good
way
to do this, just have to find it...

I think you've mistaken the facts. A hydrometer or refractometer can
be used to monitor the progress of fermentation, not to give estimates
of ethanol content. You said you are doing this as a hobby and you
said that you have an engineering background. You are asking for a
scientific method to estimate ethanol content. You are not likely to
find it at the hobby level, especially considering the complex
biological background. Why not just work like an engineer and use a
hydrometer or refractometer to monitor the progress of your
fermentation?

Evan

2007-06-14 00:41:59 UTC

Permalink

Post by d***@hotmail.com
I think you've mistaken the facts. A hydrometer or refractometer can
be used to monitor the progress of fermentation, not to give estimates
of ethanol content. You said you are doing this as a hobby and you
said that you have an engineering background. You are asking for a
scientific method to estimate ethanol content. You are not likely to
find it at the hobby level, especially considering the complex
biological background. Why not just work like an engineer and use a
hydrometer or refractometer to monitor the progress of your
fermentation?

On one hand you're right of course- both of those items can be used to
gauge fermentation progress, and homebrewers typically do things just
that way--note the starting specific gravity, take readings until they
stabilize, note finishing gravity, and from the difference you can
find your alcohol content. Going that route though for one thing
doesn't really give continuous readings, which I'd like, and also is
an avenue for contamination (you have to open the container to take a
sample) and wastage (generally it's believed to be best practice to
discard the sample at risk of contamination if you re introduce it to
the bulk liquid)

The reason I'm interested in devices is in that vein--I could easily
seal my bucket/bottle/whatever around a probe or sensor lead, and if
nothing more glance over at a display to get an idea of how my stout
is coming (or if I wanted to get really fancy, collect and compile the
data somehow)

Since my background is in electronics I wanted to explore my options
there first, but I have taken a look at refractometers,but I'm under
the impression that the type of device I need, which would be able to
read from bulk solution in a pipe or tube, rather than a sample, are
generally industrial make and rather expensive. A hydrometer would be
the easiest option in terms of equipment, but the foam and debris you
generally get in an active fermentation make reading it accurately
(and ensuring that it's floating accurately) a problem as far as I've
thought about it.

David Stone

2007-06-14 11:53:50 UTC

Permalink

Post by Evan

The impedance spectroscopy idea seems to fit, then, or you could
try just measuring conductivity - lots of probes/meters available
to do that. The reading should change over the course of fermentation
and settling.

Gregg

2007-06-14 10:07:25 UTC

Permalink

I used impedance spectroscopy on slurries as a quick way to measure the
solid phase properties.
The equivalent circuit was a nightmare, so I used a neural net to
analyze the cole-cole plot..
The biggest problem from your end would be obtaining the large number of
known samples to train the neural net.
I was surprised at how accurate it was.
The neural net software I used was cheap - $50.00. I used a good
impedance meter and swept the frequency from 100Hz to 10MHz.
I suspect your frequency range can be shorter if you are just looking
for an indicator. (maybe you can build or find a rudimentary impedance
unit)? I suspect your impedance measurements don't have to be accurate,
just consistent.
I was able to estimate surface area, p-size, % solubility, and X-tal
phases in one 30 second sweep. It may work for your project.
In any case, it should be fun to try.

Gregg

David Stranz

2007-06-14 16:48:16 UTC

Permalink

Post by Evan
Hi all, coming from an electronics/engineering background so I
apologize if there's an easy answer to this, I haven't come
across it yet...
I'm interested in being able to sense/measure alcohol
fermentations in
a hobby situation, say home brewing or winemaking, where
normally one would have to open the vessel and take samples in
order to see specific gravity via floating hydrometer or hand
held refractometer. There are a number of problems involved, one
being tha the solution of
course is not just alcohol and water, there are many other
chemicals present, as well as sediment, yeast and other things
that impinge upon
clarity (Which I think would preclude the near-IR sensor that I
saw someone mention in this group's archives)
I have not seen any comercially available sensor that measures
ethanol
in solution directly; i was thinking perhaps capacitance or
resistance
could reliably be an indicator, but as I mentioned before there
are acids among other things present which I'm sure would render
that kind
of reading useless.
The only thing resembling a lead I have is using infrared to
observe the CO2 bubbles leaving the air-trap on top of the
sealed vessel; if I
could get a reasonable estimate of the volume per bubble I think
I could work backwards through fermentation chemical formulas to
arrive at the portion of alcohol being produced. Now i'm
wondering if I could find some sort of sensor that does ethanol
vapor (e.g., a breathalyzer type sensor) and expose it to the
CO2 exhaust from the fermentation and get a reliable reading
there, then i would just have to make some correlation between
the reading in the vapor and what is in the emitting solution.
Any thoughts would be greatly appreciated; I'm sure there's a
good way
to do this, just have to find it...

If it ain't broke, don't fix it - you already have a technology
that works - your hygrometer - you just need to monitor its
readings automatically.

Why not attach something to it that would allow you to sense its
position remotely? I'm thinking a tiny mirror or reflective tape;
bounce collimated light from a laser pointer off the tape, and
measure a change in angle of reflection as the hygrometer level
changes. Or attach a gradient film and measure the intensity of
the beam. Or use a cylindrical lens to spread the laser beam out
into a line and attach something tho the hygrometer that will block
more or less of it as the level changes. You're an EE - that kind
of photo-optic circuit shouldn't be hard.

I don't know what your fermentation vessel looks like, but if it's
a 5-gallon jug like a lot of people use, you could seal a clear
plastic or glass tube to the top so that the hygrometer would be
visible through that. TAP Plastics sells tubes / cubes / other
shapes that could be adapted. Your bubbler would go on top of the
tube, or as a separate vent from the vessel.

You might have to recalibrate the hygrometer for the added mass of
whatever you attach to it unless you can figure out a way to sense
position without modifying it.

aubrey

2007-06-15 05:17:58 UTC

Permalink

Would you be willing to develop a method not for yourself, but for the
whole hobby community, i.e., a product?

There was literature involving optical fibers run through turbid
solutions published back in the 70s. Even though the light is totally
reflected, the wave function extends out into the solution, and the
absorbance spectra was acquired, if I remember the articles after 20
years.

I do happen to have at hand some near IR spectra of a water and an
ethanol sample from specimens that were handy, i.e., perhaps
contaminated. These specimens show absorbance for water at 972 nm,
and ethanol at a couple of peaks, including 908 nm. I haven't checked
these values against literature.

I would try to find a couple of diodes that emit at those two
wavelengths, run them through a fiber in the solution, and monitor the
absorbance. There is plenty of mischief to keep you busy as an
engineer, e.g., modulating the signal (in old language and technique,
"chopping") to eliminate stray light and electronic DC drift. Finding
the right length of fiber to give good sensitivity.

Sounds like fun. Also, every town in Minnesota seems to be building a
corn to ethanol plant. May be a good project to know a lot about.

Gregg

2007-06-15 10:34:21 UTC

Permalink

Post by aubrey

Would you be willing to develop a method not for yourself, but for the
whole hobby community, i.e., a product?
There was literature involving optical fibers run through turbid
solutions published back in the 70s. Even though the light is totally
reflected, the wave function extends out into the solution, and the
absorbance spectra was acquired, if I remember the articles after 20
years.
I do happen to have at hand some near IR spectra of a water and an
ethanol sample from specimens that were handy, i.e., perhaps
contaminated. These specimens show absorbance for water at 972 nm,
and ethanol at a couple of peaks, including 908 nm. I haven't checked
these values against literature.
I would try to find a couple of diodes that emit at those two
wavelengths, run them through a fiber in the solution, and monitor the
absorbance. There is plenty of mischief to keep you busy as an
engineer, e.g., modulating the signal (in old language and technique,
"chopping") to eliminate stray light and electronic DC drift. Finding
the right length of fiber to give good sensitivity.
Sounds like fun. Also, every town in Minnesota seems to be building a
corn to ethanol plant. May be a good project to know a lot about.

Just an FYI.....
They make hand held Raman units that can read through glass or from a
distance of 10's of feet.
I don't think those units are cheap........
Not as much fun as building something that works.

Gregg

Evan

2007-06-15 20:35:41 UTC

Permalink

Post by aubrey
Would you be willing to develop a method not for yourself, but for the
whole hobby community, i.e., a product?
There was literature involving optical fibers run through turbid
solutions published back in the 70s. Even though the light is totally
reflected, the wave function extends out into the solution, and the
absorbance spectra was acquired, if I remember the articles after 20
years.
I do happen to have at hand some near IR spectra of a water and an
ethanol sample from specimens that were handy, i.e., perhaps
contaminated. These specimens show absorbance for water at 972 nm,
and ethanol at a couple of peaks, including 908 nm. I haven't checked
these values against literature.
I would try to find a couple of diodes that emit at those two
wavelengths, run them through a fiber in the solution, and monitor the
absorbance. There is plenty of mischief to keep you busy as an
engineer, e.g., modulating the signal (in old language and technique,
"chopping") to eliminate stray light and electronic DC drift. Finding
the right length of fiber to give good sensitivity.
Sounds like fun. Also, every town in Minnesota seems to be building a
corn to ethanol plant. May be a good project to know a lot about.- Hide quoted text -
- Show quoted text -

Audrey-
(Apologies if this double posts, I thought I replied this morning but
cannot see it so far, i'm assuming google groups ate it)

I'd definitely be interested in making my findings available either in
a polished product or in DIY documentation form depending on how my
project goes. Lots of mischief is right too! But neat idea, I will
definitely look more in that direction :)

Cheers,
-Evan

alex

2007-07-04 04:47:07 UTC

Permalink

Post by Evan

Audrey-
(Apologies if this double posts, I thought I replied this morning but
cannot see it so far, i'm assuming google groups ate it)
I'd definitely be interested in making my findings available either in
a polished product or in DIY documentation form depending on how my
project goes. Lots of mischief is right too! But neat idea, I will
definitely look more in that direction :)

This one has an ethanol scale:
www.anton-paar.com/ap/apinternet/html/default/cxsn-5nufkh.en.0.jsp