and if you do see a pulse, you need to check the duration between the pulses varies with load (in case it’s just a comms request or indication of life). In fact, thinking about it, if the IR led was also a pulsed output there would most likely be some form of scaling/units written on the meter face eg 1000imps/kw etc, I can’t tell from the pic, nor do I know that that text must be there for IR output.
The pulse counter has a RJ45 plug and can plug into the emonpi, I’m not sure what an “Arduino TX” is, if it’s a post 2015 emonTx, it will plug in as per the emonPi. Otherwise, the plug can be chopped off (or a suitable socket used) and the 3 wires connected directly.