So the first question to ask is, what is correct? Next is how is something being measured?
If you calibrated your probe properly and you are using temperature compensation, there is not much else that is going to be more accurate than that. When you use external methods like refractometers or external devices that use the same method as the Apex of conductivity, how do you know they are calibrated? Do they take into account the temperature of the water?
Now to answer the second question. You can use your tank to "calibrate" the probe, however unless you REALLY know what you are doing, because of the answer I gave above, this may be a very bad idea. I have just recently done this (the reason for doing this may come out in a future post), but only after CAREFUL calibration of two refractometers using Two Little Fishies "AccuraSea" and getting my water to exactly what those said was 35 (repeatedly testing) did I do it. Still, that could be anywhere from 34.7 or 35.3.
I do NOT recommend this process for the average hobbyist. If you calibrate your conductivity/salinity probe with the 53000 solution, and you readings are consistent but not matching your refractometer or other device, make sure those are calibrated and do not forget that temperature plays a role.
Hi Terence, thanks for the reply, and not meaning a hijack, just threw it out there. I've used both a standard, calibrated with AccuraSea (as well as a few other calibration solutions) ATC refractometer, as well as a completely digital, ATC corrected, calibrated, Milwaukee MA887 Seawater refractometer. On my "classic" lab-grade probe apex, I use the temp probe as connected to the salinity module, floated the calibration solution, beat the probe as best i could to remove bubbles, etc, and have never gotten a reading close to 35. It's always in the 32 to 33 range. While consistent, it's never matched either my analog or digital refractometer. On my "new" apex, I did the same calibration, same result.
Both of my refractometers match one another.
Actually, I've gone through probably 6 of the calibration packets and either the Apex probe doesn't like what's in hw-marinemix reefer salt, or both of my other, calibrated, refractometers are wrong. I guess I'm just getting tired of ordering more packets as there's no place to pick them up locally, and they're not exactly free
If I were to use the tank to calibrate the probe, what salinity should I choose when calibrating? None of the default options seemed applicable to me, so I just didn't bother with it.
Honestly, I know at the end of the day, as long as the readout is not varying much, the water is likely AOK. It's just the OCD in me that wants the apex salt gauge to read what I believe it should be reading.
(love that wiper)
