The X1 in that schematic is the BNC connector.....basically that schematic is for orp...I have another for PH if you want it, well basically you can remove the 2 variable resistors and thats all the one that is on the orp is a set it once and never again kinda dealy...
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500G Mixed Reef

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Electrician, Electronics Technician, I can help with any electrical questions you might have!!
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Kevin
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