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Robusto
02-16-2012, 11:21 AM
OK guys and gals, time for my dumb question of the day-
How do you “calibrate” a hydrometer? In other words; how do you check to see if it’s reading properly? For a thermometer it’s pretty easy- just put it in boiling water and it should be at 212 F. But is there a way to test a hydrometer? Like add X grams of sugar to X ml of water and it should read 1.XXX. All of the ways that I have found on the inter-web have been for 1.0000 i.e. distilled water at a specific temp. The other methods calibrate at 1.004, but my new hydrometer only goes from 1.060 to 1.130…. so the distilled water method will not work, and I cannot find out if the other method will scale up properly to give a higher reading.

The reason that I ask is that I got a new hydrometer that is susposed to be more accurate (it measures a smaller range of gravity and the numbers are further apart), but the numbers look weird, like the paper (or whatever they are typed on) has slipped in the glass tube.

thanks

Soyala_Amaya
02-16-2012, 11:24 AM
Plain ol' water should read at a flat 1.000. If it's off one way or the other, then your hydrometer is off.

Dan McFeeley
02-16-2012, 11:32 AM
Take a look here:

http://www.byo.com/stories/projects-and-equipment/article/indices/29-equipment/414-calibrate-your-hydrometer-and-fermenter-techniques

Some good info, with detail!

--

jthoward013
02-16-2012, 11:34 AM
if that hydrometer only goes down to 1.060 you are in trouble to start. most meas will start out higher and you could read them but they end really low beyond the reach of your hydrometer like in the 1.020-0.990 range

triarchy
02-16-2012, 11:47 AM
For mead, the working SG range of a hydrometer should be around 1.160 to .990 (this is just a rough estimate of range as Im at work and I cant see mine for reference). This should cover you for beer too Id imagine. Having yours stop at 1.060 will not be very helpful once you get about 1/2 finished with a fermentation, as your mead will be below 1.060 by then.

Robusto
02-16-2012, 12:08 PM
Thanks guys. I should have noted that this one is part of a set of 3. One goes from 0.980-1.020, the next goes from 1.000-1.070, and the third goes form 1.060-1.130. Itís the last one that Iím concerned with. The idea here is that by stretching the numbers out, you can get a more accurate reading. I got these primarily for brewing beer, but thought that because of the wide range I could also cover mead.

Chevette Girl
02-16-2012, 01:31 PM
Those should be nice and accurate then... If you've got one that goes up to 1.070, then make something with sugar or salt and water to 1.070 and check the one you're concerned with against that. If the paper's shifted it should be a straight "add/subtract this much", hopefully.

Loadnabox
02-16-2012, 02:16 PM
Use distilled water, the mead calculator, and regular table sugar. Since it's literally 100% sugar it's a fixed value that you can get a specific SG with (unlike honey whose sugar content varies)

For instance, according to the mead calculator, to get an SG of 1.070 a total volume of 1 liter would require 186 Grams of sugar (measured on a good scale).

Place the sugar in the bottom of a beaker or something that can measure very accurately. Add water up to 1 liter, mix until sugar is completely dissolved.

Arden
02-16-2012, 06:05 PM
It's my understanding that hydrometers are calibrated by the manufacturer at a particular temperature. For example, mine was calibrated at 60* F. It should say on the hydrometer or the package it's in what that temperature is. I tested my new one in plain water (distilled would be better but I didn't have any) at 60* F. Instead of 1.000, as it should be, it read 1.004. Now whenever I take a reading with it I make that adjustment for what I will record at the SG.

JamesP
02-16-2012, 08:46 PM
Sounds like you may have a distillers hydrometer, which covers a narrower and higher sg range, for measuring sg of spirits.

My "wine & beer" hydrometer is calibrated for 20C or 68F, and has a corrections table if the temp of the sample is different to the standard.


For calibrating, apart from pure water = 1.000, you can also use something like:



262g of Sugar in a total volume of 1Litre is sg=1.100 at 68F

or


2.215 lb of Sugar in total vol of 1 Gal (US) is sg=1.100 at 68F

Robusto
02-17-2012, 11:21 AM
thanks everyone. that is the info that I was looking for.

-F

Braxton
02-17-2012, 06:22 PM
A little off topic, but you mention checking the calibration of a thermometer in boiling water - it's actually more accurate to check the temperature in ice water. Water will boil at different temperatures depending on altitude and other factors. Many digital thermometers with automatic re-calibration will ask you to crush ice, fill a glass with it, add cold water, and wait about 10 minutes, then take a reading and calibrate to 32 degrees.