Which to trust?

[tmccaffery]

I have a digital Milwaukee refractometer and Apex probe. I calibrated the Milwaukee using supplied distilled water and 35ppt solution both measured correct. The Apex I used manual calibration using 53,000 solution leaving in sump overnight. When done it measured 34.9ppt on Apex. Now my tank reads at 35.8 and Milwaukee reads 39. I was figuring maybe 2 degrees or so off but by this much?

My tank has evaporated so that's why the high readings. When I mix salt which one should I go with?

According to neptune probe is calibrated if reads 34.9.

 

[Uncle99]

When calibrated, neither would be that far off from one another.
Something else is wrong.

 

[tmccaffery]

Like what?

 

[thegrun]

I really don't trust conductivity probes for more than a ballpark number. They are very prone to electrical interference.

 

[tmccaffery]

Would it be more accurate if I got the PM2 module? Just curious.

 

[lapin]

Milwaukee refractometer. I this we trust. Recalibrate it using the 35ppt solution. It should be right on the next day. I have 3 refractometers and they all hold the setting. One is pretty rusted and still works.

 

[water is wet]

I've got two Milwaukee refractometers that are both off by at least 2 points and they very everytime they're not as reliable as some think. The 1st one worked great for a couple of years but the second one only lasted a few months before it started having trouble.

 

[tmccaffery]

So what you suggest to do then? Get another refractometer?

 

[FullBoreReefer]

I agree, I ONLY use my Apex probe to notice changes NOT for an accurate reading. I still use my refractometer though.

 

[tmccaffery]

Interesting I read that Milwaukee has a 2-3 degree variance. Can anyone recommend a refractometer that is more accurate?

 

[tmccaffery]

VeeGee I heard is the best but wow $111 dollars

 

[AlSimmons]

Couldn't you just get a floating glass hydrometer and call it a day?

FWIW I've been using one for a LONG TIME and my parents used to use the same thing back in the late 70's early 80's. Here it is 2018 and the design is still the same. Go figure...

 

[tmccaffery]

Like this:

https://www.ebay.com/itm/Fish-Tank-...312551&hash=item3adf016e7a:g:jDwAAOSw~oFXFYcG

 

[tmccaffery]

Got one off of Ebay now... I will try that

 

[ReeferNoob4ever]

I have been using a hydrometer (the same one at that) for 13 years now. Still works like a champ!

 

[Sisterlimonpot]

I would trust the recently calibrated Milwaukee. The reason why I say that is because the Milwaukee is extremely straight forward with calibration. With the Apex probe there are so many little things that can go wrong when calibrating such as: a wet probe before starting calibration, trapped air around the probe, tank water making it's way into the solution bag, temp variations between the salinity probe and temp probe.

Plus I couldn't make out what you meant by, "The Apex I used manual calibration using 53,000 solution leaving in sump overnight" Please clarify if you allowed the probe to sit in calibration fluid over night or that after calibrating it, you left the probe over night before taking readings. If the answer is that you left it calibrating over night, can you shed some light as to why?

 

[tmccaffery]

i put calibration fluid overnight in sump

 

[avery155]

I have same setup as OP, my Apex reads low, and 34.9 in solution. I have wires completely seperated so no electrical interference l, as well as shut off all other equipment. I don't trust it for anything other than hey look it decided to go up today, then hey other went down the say before (even tho tank is equipped with ato).

If you wiggle it it goes up, tip it upside down and it reads 50+ ..

Milwaukee just plain works, everytime.

 

[carrots]

I am another that still uses a hydrometer. In fact it is the only one I have ever had for over 40 years. Damn the years went by so fast..