Perseverance pays and in my case frustration lost out!
Calibrating the salinity probe on the Apex is a bit of a nightmare! Honestly, I’ve lost track of how many videos and posts and threads I read over the last few weeks trying to identify the root cause of why I’m having such a hard time calibrating the darn thing!
Some were more useful than others, some whimsical at best, but it took a combination of about a handful of them to come up with what finally worked for me.
These are the steps I took, perhaps they’ll help somebody else or maybe they won’t but, I’ll post them here just in case. I read quite a few threads about how having the probe cable next to power can introduce unwanted noise, stop by the electrical department, and got a couple of Clip-on Ferrite ring core RFI/EMI noise suppressors for both ends of the probe cable.
Word of warning on the clip-on Ferrite rings, they rust, so do your best to keep them sealed and away from saltwater. I wrapped the one closest to the probe in electrical tape and then covered it over with high shrink heat shrinks.
1. Calibrate your temperature probe, I cannot stress this enough if you fail to do this part don’t even bother with the rest. I used a newly acquired Hannah salinity tester with a built-in temperature to calibrate mine.
2. Drop your tank temperature to 77°F (wait for it to become stable with minimum fluctuations).
3. Run the calibration of the salinity probe directly from the Apex display and not from fusion! Fusion has way too much lag and waiting for the probe reading to become stable works best from the display.
4. Float the reference solution in your tank for a minimum of 30 minutes.
5. Make sure the temp probe and the solution are in the same vicinity to each other. The closer the better.
6. Remove the probe from your sump and clean it off with RO/DI water, it’s best to let the probe sit outside drying off for a minimum of an hour once it’s been cleaned. I have no patience for that so I use the blow dryer on cold air for about 3-5min.
7. At the apex display navigate to the probe calibration setting for your salinity probe and start your salinity probe calibration process.
8. When you get to the part about inserting the salinity probe into the reference solution, set yourself a 15-minute timer, placed the probe in a solution, and swirl it around gently for the entire 15 minutes. Note: if you happen to be watching your display, The reading will settle a couple of times but keep creeping up, mine finally ended up settling well above 0700 and I still had about three minutes left on the timer.
9. Once it settles and you hit next on the apex Display module, congratulations you’ve calibrated your probe. Go ahead and take it out of the solution and swirl it around in RODI water for a few minutes before placing it back into the sump.
31.6 ppt roughly equates to 1.023sg, which is what the Hana checker shows, after it was calibrated.