How accurate is your hydrometer?!!

[peebee]

Tilt is good, but not sure what it gives you the open-source ispindel for about the third of the price ?

"Good"? Are you sure about that? I have to hack the output of my Tilt to get any sense out of it. As the title of this thread is "how accurate is your hydrometer" I think it pretty well excludes "Tilts" and their somewhat uncertain accuracy.

In my current brew the Tilt is chucking out:

Which means my proclamation earlier in this thread (yesterday, i.e. that the beer is "finished") was rubbish (the yeast is new to me - a detail users of conventional hydrometers can ignore). But this output is also hacked (selectively "calibrated") else by this time , day 4, the Tilt would have been outputting garbage. Yesterday's post also indicates how much faith I have in the Tilt's output, in that I'm backing it up with a more reliable instrument.

 

[Edison]

I think I might give the Tilt a miss then, especially at the price!

 

[gingerneil]

"Good"? Are you sure about that? I have to hack the output of my Tilt to get any sense out of it. As the title of this thread is "how accurate is your hydrometer" I think it pretty well excludes "Tilts" and their somewhat uncertain accuracy.

In my current brew the Tilt is chucking out: View attachment 28054

Which means my proclamation earlier in this thread (yesterday, i.e. that the beer is "finished") was rubbish (the yeast is new to me - a detail users of conventional hydrometers can ignore). But this output is also hacked (selectively "calibrated") else by this time , day 4, the Tilt would have been outputting garbage. Yesterday's post also indicates how much faith I have in the Tilt's output, in that I'm backing it up with a more reliable instrument.

Ah, ok! I assumed at that price that it would be 'good'.. maybe not then! I have found my iSpindel to be very close to my measurements - within 0.002 generally, and definitely reflecting the overall trend so I can see when fermentation is stopped. These devices also provide temp too - and thats handy for controlling matts etc.

 

[zeptobrewer]

I'm half tempted to get a pycnometer to have a more accurate source of calibration. Should probably wait until I've got enough brews under my belt for it to actually matter to me, so I'll add it fairly far down this infintely growing shopping list.

 

[peebee]

I'm half tempted to get a pycnometer to have a more accurate source of calibration. Should probably wait until I've got enough brews under my belt for it to actually matter to me, so I'll add it fairly far down this infintely growing shopping list.

Good shout! Folk don't need to use a pycnometer all the time, but they do provide a reliable calibration point for the "everyday" instrument.

But the shopping list won't end with the pycnometer. They cost as little as a fiver each (delivered) from China. You don't need built-in thermometers or "calibrated" bottles (you "calibrate" them, i.e. figure out the exact volume, yourself). But you will need decent weighing scales if using 25ml bottles (weigh to +/-0.01g reliably). But for calibration you could get 50ml or 100ml bottles and ease up on the accuracy of the weighing scales. A 1litre bottle (if you could get a pycnometer so big) would work with decent kitchen scales with a bit better than +/-1g accuracy.



I've been working on getting this stuff right for 5 or 6 months. Some of my earlier posts (on Jim's) were a bit muddled (temperatures of "reference" and other such detail) so be careful of that if you come across it. But the stuff in this thread should be good.

You don't need to work out water's density for the "reference", plenty of folk have done that for you. E.g. Water Density Calculator (you only need 3 decimal places).

 

[matt76]

My original hydrometer used to read 1.000 in water at 20degC but I think the paper must have slipped at some point (probably due to putting it in hot wort) as I eventually discovered it was reading 1.004.

So I bought a new one..... that read 1.003 from the get go and I do still check it occasionally. Rather than keep wasting money I just remember to write down the "measured" and "corrected" values in my notes. However.....

Two things have jumped out at me reading through this thread:

1.

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

Well I know I have very hard water so this is interesting.

2. Is the error constant, i.e. if I'm out by 0.003 at 1.000 will I still be out by 0.003 at 1.050 (I was wondering this the other day).

Oh, and one other source of error, if you're making a really dark beer you can't always see through the sample to read the hydrometer, hence I don't actually know the exact OG of the Baltic Porter I made the other day except that it's "north of 1.080", though some might argue that at this strength the exact ABV% becomes somewhat irrelevant anyway!

 

[strange-steve]

1.
Well I know I have very hard water so this is interesting.

While this is technically true, for the TDS of typical tap water the inaccuracy is negligible.

2. Is the error constant, i.e. if I'm out by 0.003 at 1.000 will I still be out by 0.003 at 1.050 (I was wondering this the other day).

I suppose it depends on the cause of the error. It seems to be fairly common for the paper scale to shift slightly in which case the error would be constant.

Oh, and one other source of error, if you're making a really dark beer you can't always see through the sample to read the hydrometer

You can read the scale above the sample though and see where the bottom of the meniscus is?

 

[Keruso]

Really??

You can, but you have to adjust readings, thankfully there are calculators to use
Refracto calculator

 

[An Ankoù]

My hydrometer consistently reads 1001 in soft water at 20C (the calibration temperature). I record what it says for OG and for FG. and treat it as if it were accurate. I'm interested in: a consistent FG over a couple of days for bottling; and the difference between OG and FG to estimate the abv. If it were 5 points or even 10 points out, it wouldn't make any difference for either of these two uses.