Hi, I've got an EmonTx v3 hooked up to measure individual circuits in my house, and I'm seeing a weird problem. First up, I'm in Australia, so running ~250V @ 50Hz. My Tx is connected via an AC adapter.
The problem I'm seeing is that when I have one of the SCT-013-000 sensors connected to a particular circuit, the Tx reads 0W on the primary (red) wire, yet I know that the circuit is drawing power, because my internet connection and a bunch of other power points are connected to that circuit (verified by switching the breaker off).
I've tested all of my CTs and all of the Tx inputs, and when the CT and input are connected to another circuit, I get non-zero readings. I've also verified that I've got the right mains wiring using one of those AC detector pen-like things. It beeps for the wire in question when the circuit breaker is on, and is quiet when the breaker is off.
Can anyone help me figure out what's going on? I wonder if there could be some way that the circuit is wired up incorrectly, such that stuff can still draw power, but the CT won't detect anything?
Thanks for any help!
Bodhi
Re: Power monitor trouble-shooting
Ah, sorry. Should this go in the "Questions and support" forum?
Re: Power monitor trouble-shooting
Do you have a feel for how much power is being drawn on that circuit? If you plug in a really beefy load like an electric kettle or toaster, does anything show up then?
Re: Power monitor trouble-shooting
dBC it's got at least a laptop charger and a few other things that draw at least 20W or so. When I was testing everything to make sure, the CTs could easily pick up the laptop charger.
Good idea about trying something powerful, I'll give that a shot...
Re: Power monitor trouble-shooting
Unfortunately, 20 W on an input that's good to 24 kW is really, really pushing the limit on what you can measure with a 10-bit ADC. You can't expect a reasonably accurate reading until the power gets towards an order of magnitude bigger than that.
Re: Power monitor trouble-shooting
Robert, fair enough. I was expecting to see something though, even if it wasn't terribly accurate. The input was precicely zero though, whereas the other inputs, such as the light circuit will "measure" < 20W, it will actually show a noise-floor of a couple of Watts when everything is off.
Re: Power monitor trouble-shooting
Have you restarted the emonTx since you plugged the CT in?
The software detects the used inputs and works those, ignoring the ones that don't have a plug in. And those do report exactly zero to emonCMS.
Re: Power monitor trouble-shooting
Yes, restarted several times. I actually took it back to my desk to disable that part of the firmware, so that all inputs are always read, and it is still reporting zero (I have 4 CTs plugged in, so that feature isn't so important for me anyway).
I tested the CT->emonTx->serial (and wireless, from a RaspberryPi) with a laptop charger plugged into the same circuit actually (it has a two-wire cord to the plug that I could split so as to clamp around one), and it could measure ~15W, but using the same CT on the active wire of the circuit itself, I get zero.
I think I might call my electrician to come and have a look.