Four instruments.. four very different salinity readings.

[gideon2086]

Refractomer - 1.030
Hydrometer - 1.025
Hannah Digital - 1.023
Milwaukee Digital - 1.027

This is a bit ridiculous. Which of these do I trust?

 

[taulgrl]

Refractomer - 1.030
Hydrometer - 1.025
Hannah Digital - 1.023
Milwaukee Digital - 1.027

This is a bit ridiculous. Which of these do I trust?

I would test each against RODI which should be 1.000 (or close to..)

 

[bnord]

also, a 1.025 standard is cheap and easily available - I'm guess only one of those is right.... smile

 

[Sean Clark]

Aside from the refractometer they are all close enough.

Lots of factors to consider. When were they last properly calibrated? Were all of the samples the same temperature? Was that temperature the same as the fluid used to calibrate the tool? The Hydrometer is probably your best bet provided that it is a seawater Hydrometer and not intended for another use.

 

[tharbin]

I agree with @Sean Clark. If you look at them and take the hydrometer as 'right' the Hanna is .002 low and the Milwaukee .002 high. That is an acceptable range. I would double check the calibration of the refractometer.

 

[vetteguy53081]

I would test each against RODI which should be 1.000 (or close to..)

Refractomer - 1.030
Hydrometer - 1.025
Hannah Digital - 1.023
Milwaukee Digital - 1.027

This is a bit ridiculous. Which of these do I trust?

Have one or two trusted LFS test salinity for you and compare with each of yours for closest or same. My guess would be Hydrometer and Hanna

 

[gideon2086]

All were calibrated this morning. All read zero with RODI. All were tested with tank water that came out of the tank seconds before being measured.

 

[zdrc]

Did you calibrate with 35ppt solution or just RODI? I believe you need to use 35ppt solution, RODI won't cut it.

 

[Sean Clark]

All were calibrated this morning. All read zero with RODI. All were tested with tank water that came out of the tank seconds before being measured.

But was your rodi 77-78 degrees?

 

[Lbrdsoxfan]

I'd lean to the Milwaukee over anything else, hydrometer a close second. We all know refractometers have a tendency to be bogus with numbers (aka you stare at them funny and they loose calibration).

 

[Snoopy 67]

When seeking any measurement it is always better to calibrate with a solution closest to the endpoint you are looking for.

 

[gideon2086]

Did you calibrate with 35ppt solution or just RODI? I believe you need to use 35ppt solution, RODI won't cut it.

I calibrated the Hannah with 35ppt. The others with RODI.

 

[TokenReefer]

if this is a vote thread - hydrometer

Edit: of those listed it has the fewest variables

 

[zdrc]

I calibrated the Hannah with 35ppt. The others with RODI.

Try calibrating all besides the hydrometer with 35ppt. As someone already mentioned, you need to calibrate as close as possible to the salinity you plan on measuring.

What type of hydrometer? The high quality glass hydrometers are supposed to be the gold standard because they don't need to be calibrated.

 

[gideon2086]

Try calibrating all besides the hydrometer with 35ppt. As someone already mentioned, you need to calibrate as close as possible to the salinity you plan on measuring.

What type of hydrometer? The high quality glass hydrometers are supposed to be the gold standard because they don't need to be calibrated.

A cheapo plastic one I picked up when I first got into the hobby many years ago.

 

[brandon429]

this sums of reef testing of all the params, excellent thread to reflect on the decisions we make on guess test kits

 

[e3pillereefer]

Apex will give you another wacky reading to puzzle over.

 

[brandon429]

when cycle trouble shooters but the first stated range without question, that always amazes me. you can literally name any ammonia number in a cycling thread and the umps will believe it and say the bacteria are dead. this kind of thread is handy to know we're all ballparking, guesstimating.

 

[Randy Holmes-Farley Verified Community Expert]

I calibrated the Hannah with 35ppt. The others with RODI.

Depending on the refractometer, using ro/di for calibration may be theoretically ok, but it may also be inherently inaccurate and it is worth checking every device in a 35 ppt standard.

Even hydrometers should be checked and must be adjusted for temp issues.

I personally wonder how much of the faith in the accuracy of glass hydrometers is based on the fact that few people test them in 35 ppt standards to actually know.

 

[Thor2j]

I calibrated the Hannah with 35ppt. The others with RODI.

Milwaukee is supposed to be calibrated with distilled water. Can't use 35ppt on it.