Conductivity Confusion

[bsstover]

Ok, so I just installed a new conductivity probe for my apex. I purchased the 53mS calibration solution from Apex and followed steps to calibrate the probe. When the probe is placed in the calibration solution, the monitor reads 34.9. When placed in aquarium reading is 31.9. Now for the confusion. When I calibrate my refractor with either the same 53mS calibration solution or my ATC calibration solution and then test my aquarium water, the reading on my refractometer is 40!!! How is this possible and what do I need to do to get my true salinity value?! Thanks for help.

 

[jgvergo]

Make sure your calibration solution is the same temperature as your tank water when calibrating the conductivity probe and the refractometer.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, the conductivity measurement needs a temperature measurement at the same time in the same fluid. So if the APEX temp probe is not in the calibration fluid, it might be measuring incorrectly.

 

[Waterjockey]

Ok, so I just installed a new conductivity probe for my apex. I purchased the 53mS calibration solution from Apex and followed steps to calibrate the probe. When the probe is placed in the calibration solution, the monitor reads 34.9. When placed in aquarium reading is 31.9. Now for the confusion. When I calibrate my refractor with either the same 53mS calibration solution or my ATC calibration solution and then test my aquarium water, the reading on my refractometer is 40!!! How is this possible and what do I need to do to get my true salinity value?! Thanks for help.

Not all conductivity standards are suitable for use in refractometers. I don't know if the apex solution is suitable or not, something to look at anyhow.
Randy has an article about refractometers, including making your own calibration standard.

http://www.reefkeeping.com/issues/2004-06/rhf/

Cheers!