Remote AC-AC sensing with EmonTX?

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(James Taylor) #1

I am currently monitoring my energy with an EmonTX but was looking at adding an AC-AC adapter for better accuracy, however it’s not really feasible to get a socket in the meter cupboard. Is it possible to monitor it from a different node (perhaps another EmonTX) inside the house, but still have the the EmonTX monitoring the energy benefit from it? I’ve seen a few forum posts suggesting that it works but can’t find anything in the wiki saying for sure.

(Robert Wall) #2

It will “work” in the sense that you will be able to take the voltage reported by one emonTx and the current reported by another, multiply the two together and get apparent power. Even that will be an improvement, because at the moment you’re multiplying measured current by a guessed value for the voltage. But for best accuracy, you need the voltage and current to be measured by the same emonTx to calculate real power, which is what you pay for.

How far away is the nearest place you can have a socket? You can extend the low voltage cable from the a.c. adapter, and then you wouldn’t need batteries in your emonTx. Or you could extend the c.t. cables and put the emonTx near a socket - or a combination of both!

(James Taylor) #3

Sorry I’ve been a bit bad in getting back to this thread. The meter cupboard is outside, and recessed into the wall and the cables to the RCD in the house go up into the attic through a cavity wall, and then drop down again into the kitchen. So I’d essentially have to run the ct clamp cables from a room, into the attic and then drop them down into the meter cupboard.

Probably looking at ~15m of cable I’d guess.

(Robert Wall) #4

That shouldn’t be a problem, if you do it properly.
I presume you can’t go straight through the wall?