You got it Craig - Salinity is measured via conductivity (at least that how the Apex does it.) I use a Osmolator with fail-safe handled via the Apex as follows...
Set ON
Fallback ON
If Cond < 34.6 Then OFF
If pH > 08.75 Then OFF
Min Time 060:00 Then OFF
If FeedC 060 Then OFF
If FeedD 030 Then OFF
This turns off the ATO if...
- Salinity drops below 34.6 PPM
- pH increases above 8.75 (I use Kalk saturated RO/DO for my top-off.)
Both events also trigger an alarm and send me a text and email.
The Set On command provides the starting point for the outlet
The Fallback command tells the outlet what to do if it loses connection to the Apex.
The feed times represent maintenance cycles such as a water change where I want the ATO turned off for a set period of time.
The Min time statement guarantees that if the outlet is turned off - it will remain off for at least 60 minutes (to prevent cycling in the event of a probe failure)
I also have an alarm,text and email set should the salinity increase to more than 35.4 PPM as this would indicate that either the ATO pump has failed, or the ATO container is empty.
I have a hard time reading 1/10th of a PPM on a refractometer, the Apex makes it very easy to be precise.