Ultimate Refractometer Battle

[aquaticlog]

I've been collecting refractometers for almost 10 years. Some would be consistent, and some would be all over the map.

I've finally sat down and shot a detailed video where I go through every single refractometer, from old school optical to the latest digital ones, calibrate them and test them against my tank seawater. Enjoy.

 

[Waters]

Nice video. I found my Milwaukee to have the same type of issues with the readings changing from one second to the next. Every time I post that people tell me it is user error lol. I always end up double checking with a normal refractometer.

 

[aquaticlog]

Nice video. I found my Milwaukee to have the same type of issues with the readings changing from one second to the next. Every time I post that people tell me it is user error lol. I always end up double checking with a normal refractometer.

Thanks, funny that Hanna does not have the same issue. And yet, Hanna's Salinity Tester.. C'mon.

 

[ca1ore]

For those that cannot be bothered to watch the video, what's the answer LOL?

 

[destro]

Hi,

I watched your video last night and thought it was great. Appreciate the time you put in to do a thorough review like this.

I used the Sybon for a long time as well but switched to the digital device about half a year ago as it gave me temperature as well.

With regards to the hand held Hanna Marine Salinity Tester, when calibrating or testing, you need to give it a little shake to release any air bubbles that get trapped in the electrodes. I didn't see you doing this while calibrating or testing. It makes a difference IMO.

I've been using this for a few months and the results are within tolerance to my Apex salinity probe. No issues here. I feel regret that you ran into some issues with yours.

With regards to the Hanna Digital Refractometer for Seawater Analysis - HI96822
I'm interested after watching your review. However, I did ask Hanna about the difference which holds me back from investing further.

"When comparing conductivity to refractometery to measure salinity, the consensus among the scientific community favors conductivity. This is because there is non-conductive material in your sample which can impact the refractive index of seawater but not the actual salt concentration. For example, if we add sugar to artificial seawater, we will see that our salinity value will increase but we have not changed the concentration of salt in the water. If we measured the salinity of that sample with our HI98319 conductivity meter you’ll notice the value is largely unchanged. It is common to have inflated values with a refractometer due to the large number of materials which will affect the density of that water outside of the dissolved salt values. For example, anti-caking agent in salt mixes, organic waste, sugars, potential non-ionic contaminants or uneaten fish food can increase the values produced on a refractometer but this would be less likely to occur on a conductivity meter like the HI98319. Added bonuses of using conductivity to measure salinity are that you no longer have a light interference, and the temperature compensation is of your direct sample and not as influenced by ambient atmosphere near the surface of a prism."

I fully agree with you - using one device to maintain stability is the most important.

For your collection and next review -- > Hanna Laboratory Research Grade Benchtop EC/TDS/Salinity/Resistivity Meter - HI5321

 

[Richard Newman]

Interesting video. And I just found your AquaticLog app/website (Really nice).

I have spent many, many hours doing research on this specific topic when two of my LFS and my own refractometer did not align. (One used a Red Sea refractometer and the other a Milwaukee device). Your best point is at the end of the video. Specific values are just numbers, consistency is what is key.

Really the only true way to obtain an absolute measurement is to evaporate all the water and measure the salt that is left.

In my research refractometers can be biased by different elements in the sample water, thus returning a value that is off from a reference source. For this reason, the scientific community uses the conductivity method to measure salinity as it is less influenced by other elements in the water sample.

A couple of notes from my research on the various devices. Some people have reported that stray light can influence the Milwaukee device and by covering the sample area resolves that issue. Though it was very interesting to see the devices fluctuate from reading to reading.

There is also another area that should be taken into account and that is the conversion from the various forms of measurements. Refractometers are light based and while it kind of tracks in a linear fashion, it isn't 100% linear. Same goes for the conductivity scale. 53uS represents the standard 35ppt. But again there is a conversion leaving room for discrepancies.

Of note is how temperature plays a large role in affecting the reading. A sample read at 20C (68F) will have a different reading at 25C (77F). Not mention in your video is that it is key to keep all testing materials at the same temperature when comparing results. Reference/calibration solutions should match the sample solution in temperature prior to calibration.

I have the new Hanna salinity/temp tester. And once calibrated with the calibration fluid at the same temp as my tank water. It matched the reading on my refractometer.

 

[tstar]

I'm very interested in this subject as I'm getting pretty frustrated with my Red Sea Refractometer not seeming to hold it's calibration. I'm looking at the Milwaukee Refractometer or the Hanna probe conductivity tester to replace/supplement it.

But I still don't know which one to get!!!!

Tim

 

[Scorpius]

I heard people having issues with the Milwaukee digital refractometer and all I can add is that it's been consistent the whole six years I've owned it. Maybe I have the magic touch or something.