Temp Control Off by .2 degrees

[ataller]

I would like another set of eyes on this oddity I noticed.

I have my heater to turn on at 78.2 and turn off at 78.5. However, my Apex is keeping my temperature between 78.1 and 78.3.
The heater is an eheim that I calibrated and then set to 81.

Have a look at the log, there seems to be a correlation with when the apex is turning the heater on and off and when the temperature fluctuates. I do not think the temp discrepancy is because of the internal thermometer of the Eheim.

 

[SuncrestReef]

This is a common mistake people make with the Apex. You need to remove the “Set OFF” command. The reason is because the Apex evaluates each line of code from top to bottom and the last line that’s True will set the output state. In your case, the Apex will turn on the heater as soon as the temperature drops below 78.2. But once the heater warms it back up to 78.2, that line of code is no longer True, so the last line in the program that is True is the Set OFF command.

By removing Set OFF, the heater will remain on until the temperature is above 78.5. Any time you want the Apex to maintain a range between two values, whether that’s temperature, pH, flow rates, water levels, etc., you should never use a Set command.

Read more about the appropriate use of Set here:

Read This First! New APEX Users: Read This Thread!

I am a long-time owner of Neptune Systems' products, and have been helping fellow controller owners in various Internet forums for many years. Some of you may have noticed that I spend A LOT of time doing so :) In all those years, I've seen patterns of things that people sometimes do which...

forum.neptunesystems.com

Also be sure to read my series of Apex tutorials for more tips and examples on a range of topics:

Articles by SuncrestReef

www.reef2reef.com

 

[ataller]

This is a common mistake people make with the Apex. You need to remove the “Set OFF” command. The reason is because the Apex evaluates each line of code from top to bottom and the last line that’s True will set the output state. In your case, the Apex will turn on the heater as soon as the temperature drops below 78.2. But once the heater warms it back up to 78.2, that line of code is no longer True, so the last line in the program that is True is the Set OFF command.

By removing Set OFF, the heater will remain on until the temperature is above 78.5. Any time you want the Apex to maintain a range between two values, whether that’s temperature, pH, flow rates, water levels, etc., you should never use a Set command.

Read more about the appropriate use of Set here:

Read This First! New APEX Users: Read This Thread!

I am a long-time owner of Neptune Systems' products, and have been helping fellow controller owners in various Internet forums for many years. Some of you may have noticed that I spend A LOT of time doing so :) In all those years, I've seen patterns of things that people sometimes do which...

forum.neptunesystems.com

Also be sure to read my series of Apex tutorials for more tips and examples on a range of topics:

Articles by SuncrestReef

www.reef2reef.com

Thank you very much.
You have excellently explained my oversight.