Hydrometer accuracy test.

[Kiwifirst]

I finally got round to checking my hydrometer today after just assuming it was accurate. If I am correct, then it looks like this reading of water at 20c is between 1.003 and 1.004

If I am reading that right, then factoring that .004 difference will help me when trying to work out my failure to hit my FG.
Flip side, would explain my high SG 's as well.

 

[n87]

if its the same one as mine (which it does look like) it will be the upper miniscus reading.
it should say it in the paper somewhere

i also take a reading without the container full to the brim

 

[Ducatiboy stu]

Actually...you are not reading it correctly, as shown in your pic.

You need a longer sample tube so you can read it from the bottom of the meniscus.

http://en.m.wikipedia.org/wiki/Meniscus

 

[n87]

Actually...you are not reading it correctly, as shown in your pic.

You need a longer sample tube so you can read it from the bottom of the meniscus.

http://en.m.wikipedia.org/wiki/Meniscus

as mentioned, i believe the one pictured is the same as mine, which has 'reading upper miniscus' on it. see attached


but i do agree that the tube is too full for an accurate measurement

 

[Kiwifirst]

Yes you are right, it is the same. So a new read using the upper meniscus looks around 1.002.[


attachment=71395:ImageUploadedByAussie Home Brewer1401004832.984991.jpg]

 

[gTrain]

If you are reading your hydrometer from the top of the meniscus for both your OG & FG, wouldn't the calculation of ABV be the same as reading from the bottom of the meniscus for both readings?

 

[Kiwifirst]

I suppose it would. 1.050 to 1.013 compared to 1.052 to 1.015 should be the same abv% right?

I think for me, it is more about knowing the discrepancy. On brew day, with all that is going on, missing my OG by a couple of points doesn't register much on my attention scale. But a week later when my focus is on FG and I look back at my recipe at least I can now think that that 1.015 is actually 1.013 which could have been my target.

 

[Burt de Ernie]

Wait, I thought the calibration test was to be undertaken in distilled water!

 

[marksy]

Yeah distilled water and either 15c or 20c. Your hydrometer should tell you what temp.

 

[TheWiggman]

If you are reading your hydrometer from the top of the meniscus for both your OG & FG, wouldn't the calculation of ABV be the same as reading from the bottom of the meniscus for both readings?

That's right. If the weight is wrong it WON'T affect the range. The hydrometer will displace its weight in water, so the denser the hydrometer the more it will drop. As the neck is air, this is the extra bit getting displaced so the range will be the same regardless of the calibration.
In reality you would be safe going OG - FG and/or correcting based on the error (eg 3 in this case). I'm surprised though, these are a quality hydrometer. French made I think.

Ed: was completely wrong.

 

[ricardo]

What is the correct reading for a hydrometer in tap water?

 

[mr_wibble]

Just so it's here somewhere:

You can buy very accurate, Australian made hydrometers from Carlton Glass.

I'm saving up for a 0-10% http://www.carltonglass.com.au/brix.htm

 

[ricardo]

Just so it's here somewhere:

You can buy very accurate, Australian made hydrometers from Carlton Glass.

I'm saving up for a 0-10% http://www.carltonglass.com.au/brix.htm

how much are they, also is the 0 - 10 not brix meaning that you would need a 0 - 30?

 

[mr_wibble]

My quote was $150.

They do have other ranges (and precisions), but I wanted an accurate finishing measurement.

Although I do realise that level of precision is probably not necessary for hobby brewing.
But I've got a thing about inaccurate measurements - I may not be able to control my brewing exactly, but at least I will have a fair idea of where it's headed.

 

[n87]

the way i see it, as long as the increments are correct, it doesnt really matter how far it is out. you will still be able to work out the ABV, and with a quick in the head calculation, you can work out the correct SG

 

[TheWiggman]

You'd still want to know how far out it is n87. It's arguably more important to know your FG than anything else to ensure that you've attenuated fully. Otherwise, bottle bombs might be on the cards.

Ed - assuming you were discounting the error (your post read like you might have been)

 

[n87]

My hydrometer is close enough to spot on for my uses (+/- 1 point) when tested at room temp with water (i do this most times while i am rinsing it)
From my understanding, you mainly need the FG to be stable more than it to be the 'right' FG. so as long as you are using the same equipment, you will see that.

 

[ricardo]

My quote was $150.

They do have other ranges (and precisions), but I wanted an accurate finishing measurement.

Although I do realise that level of precision is probably not necessary for hobby brewing.
But I've got a thing about inaccurate measurements - I may not be able to control my brewing exactly, but at least I will have a fair idea of where it's headed.

imagine breaking that !!

 

[Black n Tan]

May be something like this is a good compromise. You won't top yourself if you break it. I HAD one for a few months but didn't replace it when it broke.

http://www.grainandgrape.com.au/products/category/search/7HYDRO+CARLT+%3C50

 

[TimT]

The other thing is, you should see how it reads at eye level. I don't remember much from high school or 1st year uni chem, but I do remember that much - that since the reading would change depending on your perspective, it is assumed that you should do the reading at eye level - I'm sure this rule holds true for hydrometers as well. The first pic is significantly above eye level, which would partially explain the unusually high reading.