Hopefully a question with a quick answer. I have a number of energy meters with a wired pulse output on the back end of each meter, not connected to the live supply. A long time ago I had them all hooked up to an Arduino, and had the Arduino logging the pulse counts to emonCMS. It made for interesting graphs. Eventually I decommissioned the system and I can’t find the sketches I used. The meter documentation shows 2 wires in use - basically 5v in and (when a pulse happens and the circuit is made) 5v back out again which is measured by the Arduino.
I’m trying to hook one of these back up to my emonTH. Do I just connect 5v from the emonTH to the input on the meter, and then the output to D3 on the emonTH? Or do I need to hook up GND somewhere along the line?