Hydrometers Vs Refractometers

[idlefingers]

I went to my lfs today to speak with the marine guy and get some advice. He mentioned how I'd need a hydrometer and I explained how I'd read on here that refractomers are far more accurate and does he think they're better as well. He said that hydrometers are quite accurate and would suffice at a fraction of the cost.

He then showed me how the hydrometer works compared to the refractomer and how the hydrometer has large spaces between the marks whereas the refractomer's marks were extremely close together and small, and therefore hard to read.

So now Im confused. How can refractomers be so much better if they're so hard to read? Are hydrometers really that inaccurate? I don't want to spend £50 if £10 will do.. But, saying that, I don't want to spend £10 on something on to regret it and go and spend £50 on a replacement!!

 

[sophos9]

Hydrometers are absolutely NOT as accurate as refractometers full stop. Refractometers are not hard to read? Buy a refractometer or you will honestly waste you cash!!

 

[idlefingers]

He got one of the refractometers out of the box and I looked through it into the light.. The lines did seem really close together and I have good eyesight. I didn't see what it's like when actually trying to get a reading, so I just took his word that it's hard to discern where exactly the water line is.

 

[sophos9]

Once loaded with some salty things work out fine - I can easily measure 1.023! Also when buying a refractometer try and buy one that has automatic temperature adjustment!

 

[idlefingers]

Okay, thanks for the help. I'll look into that.

 

[andywg]

It all depends on the equipment being bought. A decent hydrometer will work just as well as a decent refractometer so long as they are used correctly.

Most refractometers that we can afford are not entirely accurate from a salinity of 0 through to 35. Therefore it is best to calibrate them in a solution that you know is 35 (salt solution) rather than one that is 0.

There is quite a heated thread on RC about whether hydrometers are better than refractometers. The best thing for a refractometer in my book is the fact that any reading doesn't have to be adjusted for temperature.

 

[norite]

I've been through a number of hydrometers - the ones you drop in the water. *ALL* of them have been 'out' compared to another hydrometer, or a refractometer. (I even took one back to the lfs coz it was showing a salinity that was too low) However, as long as you can compare/calibrate the hydrometer to a known salt concentration, and adjust accordingly, then you should be OK.
My present hydrometer is out by 0.03, as in it is showing a salinity of 1.023, when in reality it should be 1.026

 

[SkiFletch]

My present hydrometer is out by 0.03, as in it is showing a salinity of 1.023, when in reality it should be 1.026

This is very common with hydrometers and the main reason I suggest refractometers. Hydrometers are very prone to drifting low. My own hydrometer started life very accurate but now reads 1.019 when in a solution where it should read 1.026... That's way too far off for my tastes. Refractometers however do not tend to drift this drastically once calibrated.

 

[idlefingers]

Refractometer it is then. Thanks for the advice everyone!

 

[idlefingers]

is this refractometer a good choice? it's £10 cheaper than the other ones I've seen.. It doesn't mention a brand name or anything..

 

[sophos9]

Looks like its got all the business!