[DivingTheWorld]

Originally Posted by d0ughb0y

I can see how this method works better. you are calibrating while the probe is picking up all kinds of electrical noise and interference coming from other probes (like ph), and power cords, etc. That's why the reading is different if you calibrate outside of the sump. Even if you take a cup of your exactly 35ppt tank water to calibrate the probe outside of the tank, you will likely not get the same reading if you put the probe in the tank due to the crap noise it is picking up. For the amount of money neptune charges for this, plus the galvanic isolation mumbo jumbo they claim, I think this should just work without going through hoops (just one of the many things that don't work well in Apex but people are afraid to talk about). your tropic marin is not affected by it right?

its still good practice to check the salinity outside of the tank to compare. salinity should be the same regardless if it is measured in the tank or outside.

Yeah, the Tropic Marin is just a glass floating hydrometer. Simple, but dead accurate. For my probe, I have the wire totally isolated from any other wires and the probe is on the opposite side of the sump chamber from my other probes. I wanted to make sure there was no possibility of interference. And I agree, that shouldn't be an issue if it was constructed correctly. They should be using some sort of shielded wire.