hydrometer calibration

hydrometer calibration

Post by Guy » Sun, 13 Jan 2002 02:09:46



"Don Shesnicky" wrote;

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...

You forgot to include your address. To late now!
Guy
 
 
 

hydrometer calibration

Post by Don Shesnick » Sun, 13 Jan 2002 03:11:58


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

Damn, a virtual loophole...I need a virtual lawyer.

 
 
 

hydrometer calibration

Post by Don Shesnick » Sun, 13 Jan 2002 03:14:25


Quote:

> You forgot to include your address. To late now!

Dang another loophole. Just so you know I don't really
exist but am fully virtual now.

The Wine Cyborg... WineBorg.

 
 
 

hydrometer calibration

Post by Stephen Cava » Mon, 14 Jan 2002 12:31:05



[snip]

Quote:
> 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.

Dan,

I just checked the issue of Brewing Techniques (vol 7, #3), and it is
claimed that indeed the error is not constant, and that it may be greater at
higher gravities. There were several reasons given, but one I recall is that
diameter of the tube often varies slightly and the thickness of the tube
glass may vary over the length as well.

Steve

 
 
 

hydrometer calibration

Post by Joe Sallust » Thu, 24 Jan 2002 20:48:48


Dan
Sorry I missed this.  Not to quible but wouldn't it be total volume vs
total mass for equilibrium?  In other words, the bulb + submerged stem
vs density of the fluid?  Since the change in submerged stem is a
smaller part of the total (depending on the manufacturer) that may
acount for the difference.  I will think it through later, it's a good
question...
Regards
Joe
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