Accuracy of broken hydrometer (top cracked off)

[clone63]

I've got a hydrometer that fell in the thief open side down, so the top 1/4" or so cracked off.. I thought I might be able to still use it, give or take a couple points off.. ESPECIALLY since I get 1.0 in water.
But in something that was previously 1.038 I got 1.044.
And something I thought was at FG of 1.01 became 1.017.
So I made a sugar water solution by calculator that should be 1.06 read to be 1.073.

I've given up considering using it except to.. test water.. apparently.
So I am just asking, by what design are the non-linear off readings occurring?
The first 2 readings are both too high by about the same amount. So that doesn't explain why water is correct. A linear progression sure isn't obvious.
Isn't it just air inside? Shouldn't it be at least accurately inaccurate?

It will bug me if I don't ask...
PS. I taped the top so it doesn't take on liquid.

 

[TexasDroughtBrewery]

uhhh, just buy a new one man LOL.

 

[flars]

Buy two new ones since this one still reads 1.000 in distilled water at the calibration temperature. Always good to have a spare on hand.

A thief is rather narrow for getting a good SG read. To easy for the hydrometer to stick.

 

[jschein]

Get a couple of new ones as spares.
Don't forget to post up to this thread https://www.homebrewtalk.com/showthread.php?t=148083

 

[dyqik]

I've got a hydrometer that fell in the thief open side down, so the top 1/4" or so cracked off.. I thought I might be able to still use it, give or take a couple points off.. ESPECIALLY since I get 1.0 in water.
But in something that was previously 1.038 I got 1.044.
And something I thought was at FG of 1.01 became 1.017.
So I made a sugar water solution by calculator that should be 1.06 read to be 1.073.

I've given up considering using it except to.. test water.. apparently.
So I am just asking, by what design are the non-linear off readings occurring?
The first 2 readings are both too high by about the same amount. So that doesn't explain why water is correct. A linear progression sure isn't obvious.
Isn't it just air inside? Shouldn't it be at least accurately inaccurate?

It will bug me if I don't ask...
PS. I taped the top so it doesn't take on liquid.

The material missing from the top means that the part of the hydrometer that is above the liquid weighs less than it should. The level a hydrometer ends up at is the height where the weight of liquid displaced by the immersed part of the hydrometer is equal to the total weight of the hydrometer. Remove some of the weight, and it will sit higher in a given fluid. You may also have shifted the paper scale a little.

 

[brick_haus]

Throw it away. It is no good any longer.