digital refractometer question

[ramarro]

Hi,
i am trying to setup a new tank (so for now no 'my tank' thread, as it's still empty) , and i am quite a newbie, so first things first i am trying to check salinity :)

now, something strange happen when using digital refractometer, that is labeled with ATC

if i put a drop of water, and press read, it shows 32ppt.
Water T is 26*C, room T is 19*C

now if i leave the glass of water used to pick a sample (again 32ppt) for a while till it cool down from 26 to 19, i get a new sample from the glass, and try again, the salinity raise of 2% (34ppt).


few questions now
1) is ATC working at all? shouldn't the ppt be the same?
2) what is the 'best' way to do use it? leave the sample reach room temperature and then trust this value?
3) anything i am missing


for the record:
- i used bi-distilled water to calibrate, at room temperature, and subsequent read report 0% correctly
- the refractometer is a green milwaukee

thanks for helping (and sorry for my terrible english)

 

[Tahoe61]

I have the green Milwaukee, mine is typically calibrated using distilled. Use this temperature conversion chart.

https://www.brewersfriend.com/hydrometer-temp/

:)

 

[Fish Fan]

I have the green Milwaukee, mine is typically calibrated using distilled. Use this temperature conversion chart.

https://www.brewersfriend.com/hydrometer-temp/

:)

I have the Milwaukee digital, and I love mine, even though it's been pointed out to me that it's not the most accurate way to test salinity, compared to some other options out there. But I love mine :)

I'm a little confused by what the OP is seeing and your reply here. I did think that these refractometers were temperature compensated. Is that not true?

Also, mine came with 35 ppt calibration fluid. Wouldn't it be best to calibrate the refractometer around the level where you know you want to test? For example, if you could only do a two-step calibration for a pH probe, you would want to use something like 7.0 and 10.1 because were will be testing around 7.8-8.4, and not like 7.0 and 4.01.

What do you think here? Thanks!

 

[Tahoe61]

I use either distilled or bottle calibration fluid if I have it.
When I measure and the devise reads 23 C I get a different reading of the same solution/sample if the device reads 26 C.
If I remember correctly the devise recommended 25 C.

 

[ramarro]

that's good, thanks for the input, i will try to standardize everything with the same temperature, probably atc isn't as smart as it should be, so if i use the same temp while calibrating and measuring i should be fine (i guess)

thanks!

 

[Randy Holmes-Farley Verified Community Expert]

I have the green Milwaukee, mine is typically calibrated using distilled. Use this temperature conversion chart.

https://www.brewersfriend.com/hydrometer-temp/

:)

I don't think one can use a hydrometer correction table for a refractometer that is not ATC, and one certainly cannot use one for an ATC refractometer which is not functioning correctly to eliminate temp effects. :)

 

[Randy Holmes-Farley Verified Community Expert]

that's good, thanks for the input, i will try to standardize everything with the same temperature, probably atc isn't as smart as it should be, so if i use the same temp while calibrating and measuring i should be fine (i guess)

thanks!

ATC functions have a range where they work, and the farther you are toward the extremes, or outside that range, the bigger the error effect will be.

Which model refractometer?

 

[BeanAnimal]

I have had (2) of those Milwaukee units... both are in the trash. I wouldn't trust them within 5ppt in either direction, at any temperature.

If they were consistent, I would live with whatever the error is, but I never found them to be consistent.

The only thing that I do trust is Topic Marin hydrometer as a base reference, I know it does not drift. I use it to set my conductivity and refractometers to match.

 

[ramarro]

ATC functions have a range where they work, and the farther you are toward the extremes, or outside that range, the bigger the error effect will be.

Which model refractometer?

it's the Milwaukee MA886
i'll check the Topic Marin hydrometer, at least to have a way to "double check" the reads thanks for the input

 

[TangerineSpeedo]

I also have the Milwaukee. I have found it is not accurate due to the household temps being much cooler than the tank temps. Most of the year the temp in the house is 20c or below. I mix my salt using the TM hydrometer and test my tanks using the Hanna handheld digital.

 

[Randy Holmes-Farley Verified Community Expert]

it's the Milwaukee MA886
i'll check the Topic Marin hydrometer, at least to have a way to "double check" the reads thanks for the input

Ah, that's part of the problem. That is not their seawater refractometer. That is a sodium chloride refractometer, so both the absolute values and the temperature corrections will be imperfect.

MA 887 is the seawater version.

To use it as best possible, calibrate as normal using water close to tank temp, then make a DIY seawater 35 ppt standard at tank temp, measure the value, and equate that with 35 ppt/ sg = 1.0264.

All of these issues are discussed here:

https://www.reefedition.com/refractometers-salinity-measurement/

 

[Miami Reef]

I really like the Milwaukee refractometer for salinity measurements. It’s very consistent for me. It has an accuracy of +/- 1-2 ppm.

I use the Tropic Marin hydrometer when I want highly accurate readings. You can’t go wrong with either option. :)