POS Hydrometer

[specharka]

As if it wasn't bad enough having to replace a hydrometer every time they get farted on, this happens...

I have owned this thing for less than 2 months. I knew that there were some calibration issues with this hydrometer but this is absurd -- more than 0.005 off???

What a piece of garbage. Just goes to show you can't rely on your measuring tools alone.

View attachment ImageUploadedByHome Brew1450742079.275363.jpg

(Measured with distilled water @ 60F)

 

[slym2none]

Mine has read 2 points high since I bought it. I am glad I knew to check it, thanks to this forum.

 

[mainiac]

The stem looks far off to one side . . . is the bulb perhaps adhering to/dragging on the side of the test tube? Try using a test vessel with a wider diameter so that it can float more freely and lessen the chance of contacting the vessel walls.

 

[Rev2010]

I've been using the same hydrometer that came with my first Coopers homebrewery kit 5 years ago. I have two others (got two more kits for the fermenters later) and keep them as backup but this one is doing great. It's stamped as made in France.


Rev.

 

[specharka]

The stem looks far off to one side . . . is the bulb perhaps adhering to/dragging on the side of the test tube? Try using a test vessel with a wider diameter so that it can float more freely and lessen the chance of contacting the vessel walls.

Trick of the lighting. It's quite free, and the reading isn't the first high side reading I've taken.

Brewed an alt yesterday, refractometer said 1.050, hydrometer said 1.055. Think I know which one to trust

 

[IslandLizard]

That's a lot! You could correct it with a couple o-rings around the top.

 

[Calder]

That's a lot! You could correct it with a couple o-rings around the top.

Great idea. i have one that reads .003 high. I got another one that reads correctly now, but will use the old one as back-up if I ever need it.

 

[myerstyson]

I'm no scientist and I'm not being a smart-ass, but I have to ask:

If you know the hydrometer is off by 0.005, does it matter?

For instance, I went into Brewer's Friend ABV calculator and input:

1.05 OG and 1.01 FG and got 5.25%
1.055 OG and 1.015 FG and got 5.25%

What's the diff? Or am I missing something "science-y" that I don't understand?

 

[Rhumbline]

I'm no scientist and I'm not being a smart-ass, but I have to ask:

If you know the hydrometer is off by 0.005, does it matter?

...

What's the diff? Or am I missing something "science-y" that I don't understand?

I guess you might be concerned that it isn't just off by .005 but that it isn't accurate.

It might be off by .005 at 1.000 but off by .009 at 1.060. Difficult to test at anything other than 1.000

 

[myerstyson]

I guess you might be concerned that it isn't just off by .005 but that it isn't accurate.

It might be off by .005 at 1.000 but off by .009 at 1.060. Difficult to test at anything other than 1.000

Oh ok. I understand now. Had no idea it could be off at different gravities. With that in mind, how do we know it is not off even if it is showing 1.000 at 60* in distilled water?

 

[Rhumbline]

Oh ok. I understand now. Had no idea it could be off at different gravities. With that in mind, how do we know it is not off even if it is showing 1.000 at 60* in distilled water?

You can make the assumption that if it is accurate at 1.000 it is probably accurate across the scale, or you could test other known liquids. An internet search will yield the SG of various liquids you may have around the house.

I don't get too wrapped up in it. I mostly use the hydrometer to get an idea when fermentation has stopped. If my beer is 4.7% instead of 4.5% it's not a concern for me.

 

[IslandLizard]

I guess you might be concerned that it isn't just off by .005 but that it isn't accurate.

It might be off by .005 at 1.000 but off by .009 at 1.060. Difficult to test at anything other than 1.000

Given the simple geometry of a hydrometer, what makes you think the measurement would be off? The difference in submerged volume of the straight thin tube is linearly proportional to the difference in gravity.

You can make the assumption that if it is accurate at 1.000 it is probably accurate across the scale, or you could test other known liquids. An internet search will yield the SG of various liquids you may have around the house.

I don't get too wrapped up in it. I mostly use the hydrometer to get an idea when fermentation has stopped. If my beer is 4.7% instead of 4.5% it's not a concern for me.

In red. That sounds more like it!

To test, you could measure out a mass of sugar and dissolve it in water to an accurate volume (or mass). With the now known gravity of your sugar solution your hydrometer (and refractometer) should read that value, spot on.

 

[Rhumbline]

Given the simple geometry of a hydrometer, what makes you think the measurement would be off? ...QUOTE]

I'm going to let the Sandia Lab type folks on here reply, but my theory was that if the weight of the "reference lump" was off then the error in accuracy would increase as the measured SG went up.

But I could be way out of my depth here. I'll defer to the eraser heads on this.

You can easily find the SG of common household liquids such as rubbing alcohol, olive oil, etc.

 

[WrQth]

If the paper in the tube isn't glued you can sometimes gently bump it to get it to line up I believe

 

[Invertalon]

My original hydrometer I bought from the LHBS I never checked and wondered why the IIPA I brewed had a FG of like 1.004... Thought for sure it was infected. When I checked the calibration in 60F distilled water found it was .004 off (too low), so then everything made more sense.

I picked up two higher quality hydrometers with smaller scales from Northern Brewer and they are both spot on at 60F. Also far easier to read, which is nice.

 

[IslandLizard]

I'm going to let the Sandia Lab type folks on here reply, but my theory was that if the weight of the "reference lump" was off then the error in accuracy would increase as the measured SG went up.

But I could be way out of my depth here. I'll defer to the eraser heads on this.

You can easily find the SG of common household liquids such as rubbing alcohol, olive oil, etc.

No need to get the nerds involved, a hydrometer is as simple as I described. It's the difference in displacement volume that's being measured on a long skinny tube.

There are different hydrometers to measure different mixtures, such as saline solutions. They all work on the same principle. The scales however, are different. There are some complications when liquid mixtures do not behave linearly due to contraction, e.g., alcohol and water. But a correctly calculated or calibrated scale should give correct readings of your samples.