I got my hands on two of these: http://www.yhdc.us/ProductShow3.asp?ArticleID=799
Without too much knowing what I was doing, connected them to my EmonPi to measure the mains of a house (200 A split phase).
I tested them with a toaster and plug-in watt-meter, then adjusted the factor in the config file accordingly.
This setup has been working in the sense that I get data, but I wonder how accurate it is.
Is there any reason why it would not be?
That kind of device is not intended for permanent installation, so I’d be worried about introducing an unwanted air gap. That would seriously harm accuracy. If it’s kept in good condition, it should be as accurate as the specification states.
If they’re built anything like these, the air gap might not be an issue. Given the TED CTs are intended to be installed in an enclosed load center (closest UK equivalent is a Consumer Unit) the likelihood of them being moved or otherwise disturbed is nil.
I have a TED 5000 with those same CTs (the ones on the page linked above) installed in my load center. They’ve operated without issue for a bit more than two years.
Looks like it comes down to “are the springs that hold the jaws closed strong enough to keep them closed?”
The mechanics seem solid (mechanics are a bit more my thing than electronics).
I take it then, there is no principal electrically problem operating these. Nice, thanks Bill and Robert!
I will keep you posted on any new insights!
No, you just need to calculate the value of your burden resistor based on the lower 40 mA output.(meaning, the burden resistor can have a larger value - 27 Ω would be a good fit), but what difference it will make regarding resolution probably means it isn’t worth changing anything.
For either of those CTs mentioned above, were modifications needed to make them safe to use?
Ive been trying to read up on exactly what is necessary to make a CT that can fit a North American wire, but im having a hard time understanding exactly what needs to be done. From what I can gather it involves moving or installing a burden resistor onto the new CT?
There’s information on our page about using the emonTx in N.America. The short answer is, if your CT is anything other than 50 mA secondary current at your maximum load, if yours is a current output one, you need to substitute the correct value of burden resistor inside the emonTx/emonPi; if yours is a voltage output one, it needs to be 1 V out at your maximum load, and you must remove the burden resistor inside the emonTx/emonPi.