hydrometer calibration

hydrometer calibration

Post by Don Shesnick » Wed, 09 Jan 2002 03:24:50



I kept getting readings on my valpolicella kit of 0.999 - 1.000 and
waiting for 0.996 to stablilize. It came as a suprise when I found my
new hydrometer reading +0.004 at 60F. It might be a good idea if your
new to wine making to calibrate yours.

Don

 
 
 

hydrometer calibration

Post by Glen Duf » Wed, 09 Jan 2002 21:39:49


Don,

Many years ago I had a similar problem then realized that the readout is
just a piece of paper curled up and held in the tubing by friction.  Mine
had slipped down and this was the real cause of the problem.  I suppose
the smart thing to do is buy another hydrometer.  I suppose an option
would be to check the reading in distilled water as that should give you
1.000 and then adjust your future readings accordingly.  You also might
be able to shake it down (or up) by tapping the tip of it on your hand.

It strikes me that these are not particularly well made unless someone
can show me that they are fixed or glued into the glass somehow thought
this is not obvious to me.  I expect not all hydrometers created equally
but I've only seen the one inexpensive style in winemaking shops?

This reminds me of the story my wife told me when she ran a small
winemaking shop back around 1970.  Their hydrometers were packaged with a
plastic ring around the middle of the hydrometer to protect it in the
box.  One of her customers was a local obstetrician who broke a
hydrometer  when he decided to try removing it with pliers by pulling the
wide end through the plastic.  I thought sliding it out the narrow end
seemed pretty obvious.  Needless to say we didn't have him deliver any of
our kids!!!

Glen Duff
----------

Quote:

> I kept getting readings on my valpolicella kit of 0.999 - 1.000 and
> waiting for 0.996 to stablilize. It came as a suprise when I found my
> new hydrometer reading +0.004 at 60F. It might be a good idea if your
> new to wine making to calibrate yours.

> Don


 
 
 

hydrometer calibration

Post by Greg Coo » Wed, 09 Jan 2002 22:39:03



Quote:

> Don,

> Many years ago I had a similar problem then realized that the readout is
> just a piece of paper curled up and held in the tubing by friction.  Mine
> had slipped down and this was the real cause of the problem.  I suppose

Hmm, all the hydrometers I have used have a glob of glue holding the paper.
I could see how this could come unsticked though.

Quote:
> This reminds me of the story my wife told me when she ran a small
> winemaking shop back around 1970.  Their hydrometers were packaged with a
> plastic ring around the middle of the hydrometer to protect it in the
> box.  One of her customers was a local obstetrician who broke a
> hydrometer  when he decided to try removing it with pliers by pulling the
> wide end through the plastic.  I thought sliding it out the narrow end
> seemed pretty obvious.  Needless to say we didn't have him deliver any of
> our kids!!!

This is too funny!!!!!

----Greg

http://www.ndsu.nodak.edu/instruct/grcook/wine/

 
 
 

hydrometer calibration

Post by Ray » Thu, 10 Jan 2002 05:35:13


Calibration is something I have to contend with in my regular job so it just
comes natural that I test mine in pure water before I use it each time.
This is so easy why not?  :o\   I have one that is over twenty years old and
one that is about 4 years old.   Slightly different styles.  They both
always test true.  I do not normally test them against a known sugar water
solution though I have.  I do frequently test a solution using both to see
that I get the same reading.

Since the scales are linear, if the hydrometer is reading off on a pure
water solution, you should be able to adjust answers by the error and be
right.  Of course they are fairly cheap so you could buy a new one too.

Ray


Quote:

> I kept getting readings on my valpolicella kit of 0.999 - 1.000 and
> waiting for 0.996 to stablilize. It came as a suprise when I found my
> new hydrometer reading +0.004 at 60F. It might be a good idea if your
> new to wine making to calibrate yours.

> Don

 
 
 

hydrometer calibration

Post by Jack Kell » Thu, 10 Jan 2002 08:28:29


Ditto on both points.

Jack Keller, The Winemaking Home Page
http://winemaking.jackkeller.net/

 
 
 

hydrometer calibration

Post by Stephen Cava » Fri, 11 Jan 2002 12:17:19



[snip]

Quote:
> Since the scales are linear, if the hydrometer is reading off on a pure
> water solution, you should be able to adjust answers by the error and be
> right.  Of course they are fairly cheap so you could buy a new one too.

I recall reading an article in "Brewing Techniques" vol 7 #3, a great
magazine which died a couple years ago, that suggested the error curve was
not simply linear, and that a hydrometer reading 1.000 in water at 60F might
in fact be off as the gravity increases. If your unit reads, for example,
1.002 in your calibration water, you cannot just subtract .002 from a
gravity reading as the error increases as gravity increases. The cheap
hydrometers typically have an error of 10% +/- This means that in a gravity
solution of 1.050 a $5 hydrometer could read between 1.045 and 1.055.  So
for $5 you get a unit that is OK for low readings, but not so great for high
readings. A more accurate scientific hydrometer which has a small range
spread over a long tube can be had for about $30US

Steve

 
 
 

hydrometer calibration

Post by Joe Sallust » Fri, 11 Jan 2002 20:43:54


That is correct, the scales a not linear, I just measured my Dujardin
Salleron hydrometer. at around 1.000 its a .40" for 10 degrees, at
around 1.100 it's around .32" for 10 degrees, that is a 20%
difference.

I have Kesslers, cheapos and the French hydrometers mentioned above
and have the ability to calibate them.  In a month or so I will have
some time available and will calibrate them and post the results.

Nice catch, I am a metrologist and always considered them reasonably
linear, that what winemaking texts usually say.

PS: Jack, I have half of those hydrometer values entered into a
spreadsheet and will post that too.  ( I got the hydrometer scales
from NIST and am hand entering them into a spreadsheet for
manipulation.)

Best regards
Joe

Quote:
> I recall reading an article in "Brewing Techniques" vol 7 #3, a great
> magazine which died a couple years ago, that suggested the error curve was
> not simply linear, and that a hydrometer reading 1.000 in water at 60F might
> in fact be off as the gravity increases. If your unit reads, for example,
> 1.002 in your calibration water, you cannot just subtract .002 from a
> gravity reading as the error increases as gravity increases. The cheap
> hydrometers typically have an error of 10% +/- This means that in a gravity
> solution of 1.050 a $5 hydrometer could read between 1.045 and 1.055.  So
> for $5 you get a unit that is OK for low readings, but not so great for high
> readings. A more accurate scientific hydrometer which has a small range
> spread over a long tube can be had for about $30US

> Steve

 
 
 

hydrometer calibration

Post by Jack Kell » Fri, 11 Jan 2002 23:31:32


Quote:
> ...I am a metrologist and always considered them reasonably linear,
> that's what winemaking texts usually say.

I always wondered what you do.  For some reason, I had you pegged as a
lab technician of some sort.  What interesting folks we have here....

Yes, texts usually imply a constant error rate, and for temperature
corrections I think they all imply this..  Indeed, this is only the
second time I have ever heard that a hydrometer error ratio may not be
constant.  A winemaker in Ohio once claimed that the error rate was
linear, but not constant, but I sort of dismissed his claim because it
flew in the face of simple logic and everything else I had read or
heard.  In hindsight, he may have been right.  It may be time for me
to recalibrate my own hydrometers with known solutions of, say, 1.000,
1.050 and 1.100....

Quote:
> PS: Jack, I have half of those hydrometer values entered into a
> spreadsheet and will post that too.  (I got the hydrometer scales
> from NIST and am hand entering them into a spreadsheet for
> manipulation.)

Joe, you are a sweetheart [don't read anything into that comment :-)].
 I look forward to reading them.

Jack Keller, The Winemaking Home Page
http://winemaking.jackkeller.net/

 
 
 

hydrometer calibration

Post by Brian Lundee » Sat, 12 Jan 2002 03:13:50


Hey Steve,

I just thought of a good marketing scheme for you.

Package up a carefully weighed amount of sugar, along with some instructions
on how much water to add it to, and sell it as a Hydrometer Calibration Kit
for $9.95.

If they want, people could buy the Deluxe kit for $14.95. That would include
the water. ;-)

Cheers
Brian


Quote:



> [snip]
> > Since the scales are linear, if the hydrometer is reading off on a pure
> > water solution, you should be able to adjust answers by the error and be
> > right.  Of course they are fairly cheap so you could buy a new one too.
> I recall reading an article in "Brewing Techniques" vol 7 #3, a great
> magazine which died a couple years ago, that suggested the error curve was
> not simply linear, and that a hydrometer reading 1.000 in water at 60F
might
> in fact be off as the gravity increases. If your unit reads, for example,
> 1.002 in your calibration water, you cannot just subtract .002 from a
> gravity reading as the error increases as gravity increases. The cheap
> hydrometers typically have an error of 10% +/- This means that in a
gravity
> solution of 1.050 a $5 hydrometer could read between 1.045 and 1.055.  So
> for $5 you get a unit that is OK for low readings, but not so great for
high
> readings. A more accurate scientific hydrometer which has a small range
> spread over a long tube can be had for about $30US

> Steve

 
 
 

hydrometer calibration

Post by Don Shesnick » Sat, 12 Jan 2002 05:50:33


Quote:
> I just thought of a good marketing scheme for you.

> Package up a carefully weighed amount of sugar, along with some instructions
> on how much water to add it to, and sell it as a Hydrometer Calibration Kit
> for $9.95.

> If they want, people could buy the Deluxe kit for $14.95. That would include
> the water. ;-)

Brian,
Exactly how am I suppose to get rich and retire if you keep giving
my ideas to Steve. :)

Don

 
 
 

hydrometer calibration

Post by Guy » Sat, 12 Jan 2002 06:41:28


When is that going on sale?
Guy


Quote:
> > I just thought of a good marketing scheme for you.

> > Package up a carefully weighed amount of sugar, along with some
instructions
> > on how much water to add it to, and sell it as a Hydrometer
Calibration Kit
> > for $9.95.

> > If they want, people could buy the Deluxe kit for $14.95. That
would include
> > the water. ;-)

> Brian,
> Exactly how am I suppose to get rich and retire if you keep giving
> my ideas to Steve. :)

> Don

 
 
 

hydrometer calibration

Post by D Schult » Sat, 12 Jan 2002 23:34:36


I'm having a little problem with hydrometers not being linear when it comes
to error. If I understand correctly, the hydrometer is going to float based
on it's weight and the amount of water, or solution, that it displaces.
Since the change in displacement is based on the thin upper extension of the
tube which is cylindrical, the change in the volume of water it displaces in
different gravity solutions is a function of height. The cylinder's volume
is equal to pi * radius^2 * height. If the radius of the upper tube stays
constant, the displacement, height, is directly proprotional to the gravity
of the solution. To be non-linear, either the radius must change over the
length of the tube or the paper scale must have been printed in a non-linear
scale. I don't see either of these as being very likely.

I should have that issue of Brewing Techniques*** around. I'll see if I
can dig it up and post the Author's basis for non-linearity.

-Dan


Quote:
> That is correct, the scales a not linear, I just measured my Dujardin
> Salleron hydrometer. at around 1.000 its a .40" for 10 degrees, at
> around 1.100 it's around .32" for 10 degrees, that is a 20%
> difference.

> I have Kesslers, cheapos and the French hydrometers mentioned above
> and have the ability to calibate them.  In a month or so I will have
> some time available and will calibrate them and post the results.

> Nice catch, I am a metrologist and always considered them reasonably
> linear, that what winemaking texts usually say.

> PS: Jack, I have half of those hydrometer values entered into a
> spreadsheet and will post that too.  ( I got the hydrometer scales
> from NIST and am hand entering them into a spreadsheet for
> manipulation.)

> Best regards
> Joe

> > I recall reading an article in "Brewing Techniques" vol 7 #3, a great
> > magazine which died a couple years ago, that suggested the error curve
was
> > not simply linear, and that a hydrometer reading 1.000 in water at 60F
might
> > in fact be off as the gravity increases. If your unit reads, for
example,
> > 1.002 in your calibration water, you cannot just subtract .002 from a
> > gravity reading as the error increases as gravity increases. The cheap
> > hydrometers typically have an error of 10% +/- This means that in a
gravity
> > solution of 1.050 a $5 hydrometer could read between 1.045 and 1.055.
So
> > for $5 you get a unit that is OK for low readings, but not so great for
high
> > readings. A more accurate scientific hydrometer which has a small range
> > spread over a long tube can be had for about $30US

> > Steve

 
 
 

hydrometer calibration

Post by Don Shesnick » Sun, 13 Jan 2002 00:26:52


Quote:
> When is that going on sale?
> Guy

It's a virtual sale, you use your own water, sugar and tools
and just send me the money.

Boy I hope this works...

Don

 
 
 

hydrometer calibration

Post by Ray » Sun, 13 Jan 2002 01:16:16



Quote:

> > When is that going on sale?
> > Guy

> It's a virtual sale, you use your own water, sugar and tools
> and just send me the money.

> Boy I hope this works...

> Don

It's a deal.  Here's $9.95 virtual money.  Don't spend it all in one place!
;o}

Ray

 
 
 

hydrometer calibration

Post by Ray » Sun, 13 Jan 2002 01:19:44


This is rather eye opening.  The scale looks linear as it is printed in the
hydrometer.  If the scale is truly linear, the error will be constant and
can be corrected for.  If the scales used in the hydrometers are wrong, that
is another ball game.  I want to do some research on this but can not right
now.

Interesting thread.  ;o\  hmmmm.

Ray


Quote:
> I'm having a little problem with hydrometers not being linear when it
comes
> to error. If I understand correctly, the hydrometer is going to float
based
> on it's weight and the amount of water, or solution, that it displaces.
> Since the change in displacement is based on the thin upper extension of
the
> tube which is cylindrical, the change in the volume of water it displaces
in
> different gravity solutions is a function of height. The cylinder's volume
> is equal to pi * radius^2 * height. If the radius of the upper tube stays
> constant, the displacement, height, is directly proprotional to the
gravity
> of the solution. To be non-linear, either the radius must change over the
> length of the tube or the paper scale must have been printed in a
non-linear
> scale. I don't see either of these as being very likely.

> I should have that issue of Brewing Techniques*** around. I'll see if
I
> can dig it up and post the Author's basis for non-linearity.

> -Dan



> > That is correct, the scales a not linear, I just measured my Dujardin
> > Salleron hydrometer. at around 1.000 its a .40" for 10 degrees, at
> > around 1.100 it's around .32" for 10 degrees, that is a 20%
> > difference.

> > I have Kesslers, cheapos and the French hydrometers mentioned above
> > and have the ability to calibate them.  In a month or so I will have
> > some time available and will calibrate them and post the results.

> > Nice catch, I am a metrologist and always considered them reasonably
> > linear, that what winemaking texts usually say.

> > PS: Jack, I have half of those hydrometer values entered into a
> > spreadsheet and will post that too.  ( I got the hydrometer scales
> > from NIST and am hand entering them into a spreadsheet for
> > manipulation.)

> > Best regards
> > Joe

> > > I recall reading an article in "Brewing Techniques" vol 7 #3, a great
> > > magazine which died a couple years ago, that suggested the error curve
> was
> > > not simply linear, and that a hydrometer reading 1.000 in water at 60F
> might
> > > in fact be off as the gravity increases. If your unit reads, for
> example,
> > > 1.002 in your calibration water, you cannot just subtract .002 from a
> > > gravity reading as the error increases as gravity increases. The cheap
> > > hydrometers typically have an error of 10% +/- This means that in a
> gravity
> > > solution of 1.050 a $5 hydrometer could read between 1.045 and 1.055.
> So
> > > for $5 you get a unit that is OK for low readings, but not so great
for
> high
> > > readings. A more accurate scientific hydrometer which has a small
range
> > > spread over a long tube can be had for about $30US

> > > Steve