Does anyone know the relationship between Hydrometer Accuracy and
Barometric Pressure?

That is, what is the inaccuracy of a Hydrometer with variations in
atmospheric pressure? I assume that accuracy would depend upon total
surface area of liquid exposed to atmospheric pressure whilst taking a
reading, but does anyone know what % of error there is in the reading?

Say you take a reading @20C and atmospheric pressure is say 1000mb and
the SG is 0.995, then what would the hydrometer read @ 1030mb? Lets
assume that the container we are measuring has a surface area of
126cm2.

Cheers,
Steve!

"OzWineKitz" > wrote in message
om...
> Does anyone know the relationship between Hydrometer Accuracy and
> Barometric Pressure?
>
> That is, what is the inaccuracy of a Hydrometer with variations in
> atmospheric pressure?

I'm sure that hydrometer readings are for all practical purposes essentially
independent of atmospheric pressure. Of course you could argue that at
increased pressure the glass envelope will be smaller, yielding lower S.G.
measurements, but I defy you to measure the difference across the normal
range of barometric pressure!

Altitude is another matter however, as the effect of gravity diminishes at
higher altitudes. In space, e.g., the hydrometer would float out of the
jar. For that matter, so would the wine.

Temperature also affects S.G. readings. My hydrometer indicates that its
readings are for liquids at 60°F, and a correction chart is included for
other temperatures.

Tom S

Yep, temp effects density, gravity does not. Air pressure won't have any
effects either.

Rob L
"Tom S" > wrote in message
. com...
>
> "OzWineKitz" > wrote in message
> om...
> > Does anyone know the relationship between Hydrometer Accuracy and
> > Barometric Pressure?
> >
> > That is, what is the inaccuracy of a Hydrometer with variations in
> > atmospheric pressure?
>
> I'm sure that hydrometer readings are for all practical purposes
essentially
> independent of atmospheric pressure. Of course you could argue that at
> increased pressure the glass envelope will be smaller, yielding lower S.G.
> measurements, but I defy you to measure the difference across the normal
> range of barometric pressure!
>
> Altitude is another matter however, as the effect of gravity diminishes at
> higher altitudes. In space, e.g., the hydrometer would float out of the
> jar. For that matter, so would the wine.
>
> Temperature also affects S.G. readings. My hydrometer indicates that its
> readings are for liquids at 60°F, and a correction chart is included for
> other temperatures.
>
> Tom S
>
>

The surface of liquids do not change the density, the proof is that you will
have the same reading putting your hydrometer directly the the primary
fermenter, or in a thin cylindre.

It's all a question of weight by volume. One litre of pure water will weight
one kg. The more sugar you put in the water, the more heavy it will get, but
it will still have the volume of one litre. On the other hand, the
hydrometer is balanced to float in pure water at the measure 1.000. It's
weight by volume has been calibrated for that. It will sink in lighter
liquids like oil, and will "FLOAT" on very dense liquids.

If the atmospheric pressure changes, the weight by volume of the liquide
and the one of the hydrometer will remain unchanged. So the readings will be
the same. If you change the temperature, the liquid may expand a little,
reducing it's weight by volume (same weight, more volume). Solids like the
hydrometer will not expand as much as liquids, so the readings may be
different at higher or lower temperatures.



"OzWineKitz" > wrote in message
om...
> Does anyone know the relationship between Hydrometer Accuracy and
> Barometric Pressure?
>
> That is, what is the inaccuracy of a Hydrometer with variations in
> atmospheric pressure? I assume that accuracy would depend upon total
> surface area of liquid exposed to atmospheric pressure whilst taking a
> reading, but does anyone know what % of error there is in the reading?
>
> Say you take a reading @20C and atmospheric pressure is say 1000mb and
> the SG is 0.995, then what would the hydrometer read @ 1030mb? Lets
> assume that the container we are measuring has a surface area of
> 126cm2.
>
> Cheers,
> Steve!

You know folks,

No offence intended, but it never ceases to amaze me the ignorance of
humanity!

I am aware of the arguement about temperature, because temperature
expands a liquid - but so does low atmospherice pressure,as does lower
gravitational force.

If you lower the atmoshperic temperature then a liquid will boil at a
lower temperature, hence its viscosity is increased at lower
barometric pressures. As does a liquid subject to lowered
gravitational force. It's simple physics! If one choses to ignore the
environment then let it be, but the scientist must consider all
factors, mustn't they?

Lets say that you are breathalized by a police officer and the legal
limit is 0.05% alcohol volume. Now lets consider if the atmospheric
pressure is abnormally low and the ambient temperature is relatively
high. Shouldn't it stand to reason that your REAL blood alcohol
reading be lower than actual at the time of reading? Should we just
simply accept the fact that the reading of 0.05 is acurate and we are
in the wrong if the reading is 0.051? NO! Not at all - there are other
differential factors working at hand, even though we may not be not
aware of them.

Then the same reasoning should apply to our Hydrometer readings
because there may be other influences working at hand that we are not
sure of.

The gravitational forces of the moon DO NOT work equivalent to the
Hydrometer reading because gravitational force is relative to weight
and distance. This is simple grade 8 science. So the weight of your
Hydrometer is far less significant than the weight of the liquid being
measured for Specific Gravity, isn't it?

This means that the liquid that one is measuring is being PULLED much
more than the Hydrometer that we are measuring with, isn't it? The
question remains, what is the significant difference of measurement?
The same question applies to atmospheric pressure, doesn't it? The
real question is, as to what degree or percentage is the actual
difference?

This question is not requested for speculation, but for actual
scientific reasoning, evidence, and calculation. Does anyone have a
scientific answer?

Cheers,
Steve!

No, pressure will not significantly change the volume of the fluid so it
will not effect hydrometer readings. In virtually all practical physics,
even involving multiple atmospheres of pressure change, fluid is considered
incompressible.

Ray

"OzWineKitz" > wrote in message
om...
> You know folks,
>
> No offence intended, but it never ceases to amaze me the ignorance of
> humanity!
>
> I am aware of the arguement about temperature, because temperature
> expands a liquid - but so does low atmospherice pressure,as does lower
> gravitational force.
>
> If you lower the atmoshperic temperature then a liquid will boil at a
> lower temperature, hence its viscosity is increased at lower
> barometric pressures. As does a liquid subject to lowered
> gravitational force. It's simple physics! If one choses to ignore the
> environment then let it be, but the scientist must consider all
> factors, mustn't they?
>
> Lets say that you are breathalized by a police officer and the legal
> limit is 0.05% alcohol volume. Now lets consider if the atmospheric
> pressure is abnormally low and the ambient temperature is relatively
> high. Shouldn't it stand to reason that your REAL blood alcohol
> reading be lower than actual at the time of reading? Should we just
> simply accept the fact that the reading of 0.05 is acurate and we are
> in the wrong if the reading is 0.051? NO! Not at all - there are other
> differential factors working at hand, even though we may not be not
> aware of them.
>
> Then the same reasoning should apply to our Hydrometer readings
> because there may be other influences working at hand that we are not
> sure of.
>
> The gravitational forces of the moon DO NOT work equivalent to the
> Hydrometer reading because gravitational force is relative to weight
> and distance. This is simple grade 8 science. So the weight of your
> Hydrometer is far less significant than the weight of the liquid being
> measured for Specific Gravity, isn't it?
>
> This means that the liquid that one is measuring is being PULLED much
> more than the Hydrometer that we are measuring with, isn't it? The
> question remains, what is the significant difference of measurement?
> The same question applies to atmospheric pressure, doesn't it? The
> real question is, as to what degree or percentage is the actual
> difference?
>
> This question is not requested for speculation, but for actual
> scientific reasoning, evidence, and calculation. Does anyone have a
> scientific answer?
>
> Cheers,
> Steve!

"OzWineKitz" > wrote in message
om...
> I am aware of the arguement about temperature, because temperature
> expands a liquid - but so does low atmospherice pressure,as does lower
> gravitational force.

Although it's true that an increase in temperature expands the volume of a
liquid, a decrease in atmospheric pressure does not. Neither does a
decrease in gravitational force.

> If you lower the atmoshperic temperature then a liquid will boil at a
> lower temperature

That's not quite correct. You must have meant "lower the atmospheric
_pressure_" - right?

hence its viscosity is increased at lower
> barometric pressures. As does a liquid subject to lowered
> gravitational force.

Huh? None of that sounds like good physics to me.

> Lets say that you are breathalized by a police officer and the legal
> limit is 0.05% alcohol volume. Now lets consider if the atmospheric
> pressure is abnormally low and the ambient temperature is relatively
> high. Shouldn't it stand to reason that your REAL blood alcohol
> reading be lower than actual at the time of reading? Should we just
> simply accept the fact that the reading of 0.05 is acurate and we are
> in the wrong if the reading is 0.051? NO! Not at all - there are other
> differential factors working at hand, even though we may not be not
> aware of them.

I'm sorry, but I don't see what all that means within the context of this
thread. Actually, I can't make much out of it at all.

> Then the same reasoning should apply to our Hydrometer readings
> because there may be other influences working at hand that we are not
> sure of.

One can only imagine...

> The gravitational forces of the moon DO NOT work equivalent to the
> Hydrometer reading because gravitational force is relative to weight
> and distance. This is simple grade 8 science. So the weight of your
> Hydrometer is far less significant than the weight of the liquid being
> measured for Specific Gravity, isn't it?

Perhaps, but so what? A small cylinder of sea water will measure at the
same specific gravity as an entire _ocean_ of the same water. The
difference in weights - or more correctly _masses_ - between the hydrometer
and the ocean does not factor into the measurement.

> This means that the liquid that one is measuring is being PULLED much
> more than the Hydrometer that we are measuring with, isn't it?

It's clear to me that you have some notions of physics that I could only
characterize as quaint.

Tom S

There's no mercury in my hydrometer! Or even in my thermometer come to think
of it --but I wouldn't like to break the thermometer in my wine.

--
Trevor A Panther
In South Yorkshire, England
Remove "SPAMLESS" from my address line to reply.
All outgoing mail is scanned by Norton
Anti Virus for your protection too!
"Romahawk" > wrote in message
om...
> wrote:
<snip> <snip>
> I'm wondering if dropping the hydrometer into your fermenter is such a
> good idea. If you accidentally break it or you are using a small
> container and it hits the bottom and breaks won't you now have a
> container of fermenting wine contaminated by mercury? I think it's best
> to stick with the glass tube for testing.
>
>
>
> --
> http://www.romahawk.com
>
> Posted via MooTalk
> http://mootalk.com

Hi Steve,
Yes I have a scientific answer, but to which topic? I came into this
late and this one is all of the place.

The effect of barometric pressure shifts in the range of +/- 30 mmHg
from 760 mmHg are miniscule, as are air density and gravity
corrections. If you read the S.G. on the hydrometer to only 3 places
there is no need to correct for it as far as I am concerned.

The definitive text in the States on this subject is Polarimetry,
Saccarimetry and the Sugars by Bates; it may be available in a good
university library 'down under', but it's pretty old. It is NBS
Circular C440 published in 1948, (I have a copy). You may be able to
get access to some ISO or DIN hydrometer calibration documents, that
is really what you need. (The book I mentioned has equations you can
consider, they are pretty involved.)

I can post a hyrdometer calibration document I wrote up derived from
this, but Clyde already added it to the FAQ he maintains.

All of this depends on the reference material, by the way. Weight and
Mass are not the same in air, the density of the object in question
must be considered. The standard reference material used to be a
well-defined Brass, it is now a well-defined Stainless Steel. (Both
are around 8/g per cc, air is around 0.0012 g/cc.) Only very precise
measurement equipment can pick up the diference.

Again, at the precision most winemakers are satisfied with,
temperature of the liquid is the only variable to correct. (The
hydrometer and liquid are assumed to be at equilibrium; they should be
at the same relative temperature after a few minutes if the difference
is extreme.)

Best regards,
Joe



(OzWineKitz) wrote in message . com>...
> You know folks,
>
> No offence intended, but it never ceases to amaze me the ignorance of
> humanity!
>
> I am aware of the arguement about temperature, because temperature
> expands a liquid - but so does low atmospherice pressure,as does lower
> gravitational force.
>
> If you lower the atmoshperic temperature then a liquid will boil at a
> lower temperature, hence its viscosity is increased at lower
> barometric pressures. As does a liquid subject to lowered
> gravitational force. It's simple physics! If one choses to ignore the
> environment then let it be, but the scientist must consider all
> factors, mustn't they?
>
> Lets say that you are breathalized by a police officer and the legal
> limit is 0.05% alcohol volume. Now lets consider if the atmospheric
> pressure is abnormally low and the ambient temperature is relatively
> high. Shouldn't it stand to reason that your REAL blood alcohol
> reading be lower than actual at the time of reading? Should we just
> simply accept the fact that the reading of 0.05 is acurate and we are
> in the wrong if the reading is 0.051? NO! Not at all - there are other
> differential factors working at hand, even though we may not be not
> aware of them.
>
> Then the same reasoning should apply to our Hydrometer readings
> because there may be other influences working at hand that we are not
> sure of.
>
> The gravitational forces of the moon DO NOT work equivalent to the
> Hydrometer reading because gravitational force is relative to weight
> and distance. This is simple grade 8 science. So the weight of your
> Hydrometer is far less significant than the weight of the liquid being
> measured for Specific Gravity, isn't it?
>
> This means that the liquid that one is measuring is being PULLED much
> more than the Hydrometer that we are measuring with, isn't it? The
> question remains, what is the significant difference of measurement?
> The same question applies to atmospheric pressure, doesn't it? The
> real question is, as to what degree or percentage is the actual
> difference?
>
> This question is not requested for speculation, but for actual
> scientific reasoning, evidence, and calculation. Does anyone have a
> scientific answer?
>
> Cheers,
> Steve!

"Joe Sallustio" > wrote in message
om...
> Hi Steve,
> Yes I have a scientific answer, but to which topic? I came into this
> late and this one is all of the place.
>
> The effect of barometric pressure shifts in the range of +/- 30 mmHg
> from 760 mmHg are miniscule, as are air density and gravity
> corrections. If you read the S.G. on the hydrometer to only 3 places
> there is no need to correct for it as far as I am concerned.
>
> The definitive text in the States on this subject is Polarimetry,
> Saccarimetry and the Sugars by Bates; it may be available in a good
> university library 'down under', but it's pretty old. It is NBS
> Circular C440 published in 1948, (I have a copy). You may be able to
> get access to some ISO or DIN hydrometer calibration documents, that
> is really what you need. (The book I mentioned has equations you can
> consider, they are pretty involved.)
>
> I can post a hyrdometer calibration document I wrote up derived from
> this, but Clyde already added it to the FAQ he maintains.
>
> All of this depends on the reference material, by the way. Weight and
> Mass are not the same in air, the density of the object in question
> must be considered. The standard reference material used to be a
> well-defined Brass, it is now a well-defined Stainless Steel. (Both
> are around 8/g per cc, air is around 0.0012 g/cc.) Only very precise
> measurement equipment can pick up the diference.
>
> Again, at the precision most winemakers are satisfied with,
> temperature of the liquid is the only variable to correct. (The
> hydrometer and liquid are assumed to be at equilibrium; they should be
> at the same relative temperature after a few minutes if the difference
> is extreme.)
>
> Best regards,
> Joe

Great post Joe.
Thank you.
lum