How accurate is your hydrometer?!!

[Trom-man76]

Just using a HMRC approved hydrometer for working out abv for tax purposes. Testing these Stevenson reeve bad boys against my original homebrew hydrometer and it's almost 2% difference!!!!!!
My old beer recipie, I thought, was 5% and was really 7%
Not complaining just surprised it was that far out.

 

[chillipickle]

Ask your self was your old recipe really 5% and the HMRC hydro was lying to be 7% for the extra revenue...only joking of course :)

 

[peebee]

I've wondered about these "HMRC approved hydrometers". Scientific (and perhaps these HMRC ones?) will be calibrated to a 4C water reference by default. Brewing hydrometers will be "calibrated" roughly to a 20C water reference. The temperature they are to be used and the "reference" temperature can be different.

The difference is put a brewing hydrometer in water at the hydrometer's "calibrated" temperature and it will read 1.000 … yeah, that's got to be right! Put a scientific hydrometer in water at it's calibrated temperature and it will read about 0.998 … na, that's got to be wrong? Nope, it's right!

Your "HMRC approved" hydrometers perhaps has a marking something like "20/4", or perhaps not because that is the default. Your brewing hydrometer should be marked something like 20/20, but probably wont because they are imprecise Noddy tools.

 

[Clint]

For the wife's benefit it measures beers at 4%.

 

[marshbrewer]

For the wife's benefit it measures beers at 4%.

Mines like that. It also has an 'about' function, i.e.

'how strong is that beer you are drinking!?!?!'

'about 3%, darling'

 

[Clint]

Amazing!

 

[lancon]

Just using a HMRC approved hydrometer for working out abv for tax purposes. Testing these Stevenson reeve bad boys against my original homebrew hydrometer and it's almost 2% difference!!!!!!
My old beer recipie, I thought, was 5% and was really 7%
Not complaining just surprised it was that far out.

2% ABV difference would be about the difference on the hydrometer of 1.000-1.015, 15 points of gravity!

 

[Galena]

I checked my hydrometer last night and in tap water at 20.1 degrees it was reading 1.006. So does that mean I should subtract .006 off all reading?

 

[lancon]

And Stevenson Reeves HMRC approved are calibrated to 20C

 

[lancon]

check your water? or get a new hydrometer? If it is that far out I wouldn't trust it at all, perhaps the printed scale is not correct?

 

[johncrobinson]

The 1.000 (plain water reading.)will not be accurate in a hard water area.

 

[terrym]

The 1.000 (plain water reading.)will not be accurate in a hard water area.

What error would you expect then?

 

[foxbat]

I checked my hydrometer last night and in tap water at 20.1 degrees it was reading 1.006. So does that mean I should subtract .006 off all reading?

That's off by a surprising amount. Have you dropped it or done anything else that would cause the label inside to slip? Yes you should subtract .006 from all readings.

 

[Cwrw666]

When you get to a certain age the accuracy of a hydrometer or any other measuring devise depends entirely on your ability to read it anymore in the gloom.

 

[marshbrewer]

To be honest, I'm not that fussed about the accuracy, more the repeatability.

For instance, if in a liquid that is really 1040, mine reads 1038, then after fermentation it is really 1012 but mine reads 1010 then the ABV calculation is the same.

Likewise, if a particular style finishes at 1015 but my hydrometer reads 1013, and the style has the maltiness that is perfect, and another style finishes at 1008 but my hydrometer reads 1006 and it has the correct dryness for that style, as long as I shoot for my hydrometer reading when brewing all is good.

OK, I might have to adjust my brewing software when I find that I always hit 2 points lower than it predicts, but that's about it

The only thing that would concern me is if the readings weren't repeatable, in other words, in a liquid that was really 1010, it would give different readings on different days despite the temp being stable. But I've never encountered that tbh.

 

[An Ankoù]

Does it really matter for the purposes of calculating abv? If my hydrometer reads the OG, say, 5 degrees to high and I use the same hydrometer to measure the FG, that'll also be 5 degrees too high. But the difference between the OG and the FG will be the same as if I used a finely tuned hydrometer so the abv calculation will also give the same result.

 

[strange-steve]

Just using a HMRC approved hydrometer for working out abv for tax purposes. Testing these Stevenson reeve bad boys against my original homebrew hydrometer and it's almost 2% difference!!!!!!
My old beer recipie, I thought, was 5% and was really 7%
Not complaining just surprised it was that far out.

I'm confused as to how you found a 2% abv difference. Did the calibrated hydrometer read a higher OG and a lower FG than your old hydrometer?

 

[strange-steve]

The 1.000 (plain water reading.)will not be accurate in a hard water area.

Unless you're brewing with sea water I don't think a hydrometer is accurate enough to notice any difference.

 

[Galena]

That's off by a surprising amount. Have you dropped it or done anything else that would cause the label inside to slip? Yes you should subtract .006 from all readings.

Brand new yesterday

 

[Clint]

...but he did have to tape it back together as the courier noticed the FRAGILE label.