The Apex conductivity/salinity probe is not of the best design. With that acknowledged, here's how to get yours working consistently and well.
First, if you've done a calibration before and it seems to be messed up, simply recalibrating it is likely not going to do the trick. You need to reset the probe software in the controller and this is not well documented but I can vouch from personal experience that it definitely works and will save you much frustration. First, disconnect the probe from the jack on the Apex controller. Now do a manual calibration. Obviously this is a sham calibration since no probe is attached, so just go through the steps quickly and finish it. Then reboot your Apex (any of the several ways to do this is fine.)
Now reconnect your probe. You're ready to do a proper calibration. It needs to be a Manual calibration, not Automatic.
For the first phase, rinse the probe well in RODI water, shake it off gently and pat the end to remove excess moisture. You really don't have to make it bone dry, although you can blow a little pressurized gas through if you want. (I wouldn't let it dry overnight as some suggest, not necessary at all.) Start the manual calibration. The number should settle pretty fast. Go to phase two.
For the second phase, make sure you have the right solution, and make sure it is at your tank water temperature. Many people just tape the opened package to the inside of the sump. Or you can put the package in a beaker of water and make a water bath in your sump. Insert the probe, make sure it's submerged, let it sit with a swish every 30 seconds or so. Wait for number to settle for several minutes at least, until you're absolutely sure it's not moving anymore, and then complete the calibration.
If you have no defective hardware or offbeat software glitch, your probe should be working now.
First, if you've done a calibration before and it seems to be messed up, simply recalibrating it is likely not going to do the trick. You need to reset the probe software in the controller and this is not well documented but I can vouch from personal experience that it definitely works and will save you much frustration. First, disconnect the probe from the jack on the Apex controller. Now do a manual calibration. Obviously this is a sham calibration since no probe is attached, so just go through the steps quickly and finish it. Then reboot your Apex (any of the several ways to do this is fine.)
Now reconnect your probe. You're ready to do a proper calibration. It needs to be a Manual calibration, not Automatic.
For the first phase, rinse the probe well in RODI water, shake it off gently and pat the end to remove excess moisture. You really don't have to make it bone dry, although you can blow a little pressurized gas through if you want. (I wouldn't let it dry overnight as some suggest, not necessary at all.) Start the manual calibration. The number should settle pretty fast. Go to phase two.
For the second phase, make sure you have the right solution, and make sure it is at your tank water temperature. Many people just tape the opened package to the inside of the sump. Or you can put the package in a beaker of water and make a water bath in your sump. Insert the probe, make sure it's submerged, let it sit with a swish every 30 seconds or so. Wait for number to settle for several minutes at least, until you're absolutely sure it's not moving anymore, and then complete the calibration.
If you have no defective hardware or offbeat software glitch, your probe should be working now.