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wangspeed

Salinity measurement face off! Hanna, Milwaukee, Neptune

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First, let me say this. I hate analog refractometers. My experience is that they go out of calibration if you look at them. Yes you can calibrate each time, but that’s a pain. Also, reading them isn’t exactly clear. Where is the line? It’s fuzzy, so which part of the line do you count as your measurement?

 

A long time ago, I switched to the Milwaukee MA887. I love it, except for one thing. It is very consistently +.002 SG. It always has been right out of the box. During DC MACNA I spoke to someone at Milwaukee about this and he was super defensive and rude. I found out their calibration standard is different than normal. I got a bottle of it and sure enough, it reads what it says it should. IMO it is -.002 SG from other standards that should be 1.026. I have tried every standard I could get my hands on. It is always +.002.

 

Strangely, a friend of mine had the Hanna version of this same checker and it is dead on accurate. Maybe Hanna calibrates it with different fluid.

 

I finally came to the realization that this is fine as long as it is consistent, and it is. It doesn’t lose calibration. Ever. Not a single time that I have tested it has it been off. I’m willing to sacrifice accuracy for this kind of consistency.

 

Along cake my current tank build with a new 2016 Apex. It has a conductivity probe. Nice! Except everyone complains about it being off. Not mine. Mine doesn’t do wonky things. It reads a little on the high side though.

 

Just a few weeks ago, I saw the Hanna salinity checker announcement. I guess they retired the old version that is almost identical to Milwaukee. Being a gadget person, I decided to get it. Besides, I hate having to go to the basement to fetch the Milwaukee. I want a dead nuts accurate refractometer on every floor of the house that has a tank.

 

My tank was a little low on salinity. I knew it was drifting due to wet skimming. Time to test out all 3 salinity probes!

 

This is dead on:

d26a5513f103ffe360ca2f0d5564104a.jpg

 

+.002 as usual (I cover the glass with my hand when it is reading)

c8d94b956ee68540f78b240817bce4b3.jpg

 

Apex is also showing high. Almost as high as my Milwaukee

7acc0fd106829b0cd7a16cd27edda456.jpg

 

There it is. Now to see how consistent the Hanna stays over time.

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Thanks! I agree, consistency is the key.

 

The benefit of a handheld refractometer is that it's inexpensive but it does have to be calibrated and sometimes often.

 

You have two different technologies there, though. Many are conductivity meters. These are measuring electrical conductivity and mapping it to specific gravity. This conversion has to make certain assumptions about the ionic composition of the fluid. That is to say, 35 pppt ASW would have a different conductivity measurement than 35 ppt saline (NaCl) solution.

 

The Milwaukee unit, though, is measuring a refractive index and converting it to specific gravity. Again, the conversion assumes a certain ionic composition to make that conversion.

 

RHF gets into some of this in a 2004 article in Reefkeeping Magazine on a homemade salinity calibration standard. If you read it through, you'd see two different recipes for a NaCl-based calibration fluid for conductivity meters and for refractometers.

 

This is probably why the two devices give you different readings. And, to be honest, neither is probably accurate even though both are precise. If you want to read specific gravity, you need a good quality hydrometer or a specific gravity meter which attempts to measure fluid density.

 

 

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So you’re happy with the Hanna? My Milwaukee crapped the bed after a few uses and a battery change, unfortunately, bought used.


Sent from my iPhone using Tapatalk

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So you’re happy with the Hanna? My Milwaukee crapped the bed after a few uses and a battery change, unfortunately, bought used.


Sent from my iPhone using Tapatalk


I don’t recall if Milwaukee does this, but try a non-rechargeable battery. I know all Hanna checkers will not work with rechargeables.

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Oops. Too soon. Forgot to answer the question. So far so good, but time will tell how well it stays calibrated. They suggest calibration once month.

It’s harder to clean though. You need to rinse with RODI. The old Milwaukee, I just rinse with tap. It’s clean enough around here to ensure the glass and sample well don’t form deposits if you wipe it off with a lint free cloth.

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The Hanna tester is the HI98319 one right? I read about it a couple of weeks ago and have been considering picking it up. Having to rinse with RODI water isn't an issue for me since I I could just swish it around in my top off water container after each use. 

 

Where did you pick yours up from? Looks to be $70 on the Hanna site and I'm curious if I can get it a bit cheaper or not.

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Thanks for the update. I just got mine in the mail I ordered during black Friday a couple of days ago. Looking forward to actually getting all calibrated and using it this weekend. 

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12 hours ago, wangspeed said:

 


I don’t recall if Milwaukee does this, but try a non-rechargeable battery. I know all Hanna checkers will not work with rechargeables.

 

 

Yeah, I was using Duracell non rechargeable. It appears the screen is reading funny. I'm sure it's out of warranty, I've not reached out. I loved it while I was using it though. 

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FYI, I have been rinseing with tap water on my hannah unit to no ill affect for about a month, i'll let you know if that continues to be the case. Also i ended up testing a new packet of solution after a month and the unit did not need to be recalibrated... so far so good! I love how handy it is, also it's temp readings are very accurate. 

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The Hanna tester is the HI98319 one right? I read about it a couple of weeks ago and have been considering picking it up. Having to rinse with RODI water isn't an issue for me since I I could just swish it around in my top off water container after each use. 
 
Where did you pick yours up from? Looks to be $70 on the Hanna site and I'm curious if I can get it a bit cheaper or not.


No it sells for MSRP everywhere. I think saltwater aquarium.com and premium aquatics are sponsors and it can be had from either of those.

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I got mine through saltwateraquarium.com with a small 10% discount and 5% cashback for a total of 15% off which was nice. 

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I stick to the refractometer and check calibration before each use; it only takes 45 seconds and leaves me no doubt. 

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